1. |
- Palmquist, Anders, 1977, et al.
(author)
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Complex geometry and integrated macro-porosity: Clinical applications of electron beam melting to fabricate bespoke bone-anchored implants
- 2023
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In: Acta Biomaterialia. - : Elsevier BV. - 1742-7061 .- 1878-7568. ; 156, s. 125-145
-
Research review (peer-reviewed)abstract
- The last decade has witnessed rapid advancements in manufacturing technologies for biomedical implants. Additive manufacturing (or 3D printing) has broken down major barriers in the way of producing complex 3D geometries. Electron beam melting (EBM) is one such 3D printing process applicable to metals and alloys. EBM offers build rates up to two orders of magnitude greater than comparable laser-based technologies and a high vacuum environment to prevent accumulation of trace elements. These features make EBM particularly advantageous for materials susceptible to spontaneous oxidation and nitrogen pick-up when exposed to air (e.g., titanium and titanium-based alloys). For skeletal reconstruction(s), anatomical mimickry and integrated macro-porous architecture to facilitate bone ingrowth are undoubtedly the key features of EBM manufactured implants. Using finite element modelling of physiological loading conditions, the design of a prosthesis may be further personalised. This review looks at the many unique clinical applications of EBM in skeletal repair and the ground-breaking innovations in prosthetic rehabilitation. From a simple acetabular cup to the fifth toe, from the hand-wrist complex to the shoulder, and from vertebral replacement to cranio-maxillofacial reconstruction, EBM has experienced it all. While sternocostal reconstructions might be rare, the repair of long bones using EBM manufactured implants is becoming exceedingly frequent. Despite the various merits, several challenges remain yet untackled. Nevertheless, with the capability to produce osseointegrating implants of any conceivable shape/size, and permissive of bone ingrowth and functional loading, EBM can pave the way for numerous fascinating and novel applications in skeletal repair, regeneration, and rehabilitation. Statement of significance: Electron beam melting (EBM) offers unparalleled possibilities in producing contaminant-free, complex and intricate geometries from alloys of biomedical interest, including Ti6Al4V and CoCr. We review the diverse range of clinical applications of EBM in skeletal repair, both as mass produced off-the-shelf implants and personalised, patient-specific prostheses. From replacing large volumes of disease-affected bone to complex, multi-material reconstructions, almost every part of the human skeleton has been replaced with an EBM manufactured analog to achieve macroscopic anatomical-mimickry. However, various questions regarding long-term performance of patient-specific implants remain unaddressed. Directions for further development include designing personalised implants and prostheses based on simulated loading conditions and accounting for trabecular bone microstructure with respect to physiological factors such as patient's age and disease status.
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2. |
- Berglund, Fanny, et al.
(author)
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Evidence for wastewaters as environments where mobile antibiotic resistance genes emerge
- 2023
-
In: Communications Biology. - : Springer Science and Business Media LLC. - 2399-3642. ; 6
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Journal article (peer-reviewed)abstract
- The emergence and spread of mobile antibiotic resistance genes (ARGs) in pathogens have become a serious threat to global health. Still little is known about where ARGs gain mobility in the first place. Here, we aimed to collect evidence indicating where suchinitial mobilizationevents of clinically relevant ARGs may have occurred. We found that the majority of previously identified origin species did not carry the mobilizing elements that likely enabled intracellular mobility of the ARGs, suggesting a necessary interplay between different bacteria. Analyses of a broad range of metagenomes revealed that wastewaters and wastewater-impacted environments had by far the highest abundance of both origin species and corresponding mobilizing elements. Most origin species were only occasionally detected in other environments. Co-occurrence of origin species and corresponding mobilizing elements were rare in human microbiota. Our results identify wastewaters and wastewater-impacted environments as plausible arenas for the initial mobilization of resistance genes.
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3. |
- Peruzzi, Niccolò, et al.
(author)
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Multimodal ex vivo methods reveal that Gd-rich corrosion byproducts remain at the implant site of biodegradable Mg-Gd screws
- 2021
-
In: Acta Biomaterialia. - : Elsevier. - 1742-7061 .- 1878-7568. ; 136, s. 582-591
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Journal article (peer-reviewed)abstract
- Extensive research is being conducted on magnesium (Mg) alloys for bone implant manufacturing, due to their biocompatibility, biodegradability and mechanical properties. Gadolinium (Gd) is among the most promising alloying elements for property control in Mg alloy implants; however, its toxicity is controversial. Investigating Gd behavior during implant corrosion is thus of utmost importance. In this study, we analyzed the degradation byproducts at the implant site of biodegradable Mg-5Gd and Mg-10Gd implants after 12 weeks healing time, using a combination of different imaging techniques: histology, energy-dispersive x-ray spectroscopy (EDX), x-ray microcomputed tomography (µCT) and neutron µCT. The main finding has been that, at the healing time in exam, the corrosion appears to have involved only the Mg component, which has been substituted by calcium and phosphorus, while the Gd remains localized at the implant site. This was observed in 2D by means of EDX maps and extended to 3D with a novel application of neutron tomography. X-ray fluorescence analysis of the main excretory organs also did not reveal any measurable accumulation of Gd, further reinforcing the conclusion that very limited or no removal at all of Gd-alloy happened during degradation.
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4. |
- von Mentzer, Ula, 1995, et al.
(author)
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Biomaterial Integration in the Joint: Pathological Considerations, Immunomodulation, and the Extracellular Matrix
- 2022
-
In: Macromolecular Bioscience. - : Wiley. - 1616-5195 .- 1616-5187. ; 22:7
-
Research review (peer-reviewed)abstract
- Defects of articular joints are becoming an increasing societal burden due to a persistent increase in obesity and aging. For some patients suffering from cartilage erosion, joint replacement is the final option to regain proper motion and limit pain. Extensive research has been undertaken to identify novel strategies enabling earlier intervention to promote regeneration and cartilage healing. With the introduction of decellularized extracellular matrix (dECM), researchers have tapped into the potential for increased tissue regeneration by designing biomaterials with inherent biochemical and immunomodulatory signals. Compared to conventional and synthetic materials, dECM-based materials invoke a reduced foreign body response. It is therefore highly beneficial to understand the interplay of how these native tissue-based materials initiate a favorable remodeling process by the immune system. Yet, such an understanding also demands increasing considerations of the pathological environment and remodeling processes, especially for materials designed for early disease intervention. This knowledge will avoid rejection and help predict complications in conditions with inflammatory components such as arthritides. This review outlines general issues facing biomaterial integration and emphasizes the importance of tissue-derived macromolecular components in regulating essential homeostatic, immunological, and pathological processes to increase biomaterial integration for patients suffering from joint degenerative diseases.
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5. |
- Ferrand-Drake Del Castillo, Gustav, 1990
(author)
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Polyelectrolyte Brush Electrodes for Protein Capture and Release
- 2020
-
Doctoral thesis (other academic/artistic)abstract
- Stimuli-responsive polyelectrolyte brushes switch as a function of pH between a charged and neutral state that affects their electrostatic interactions with other charged molecules like proteins. Adjustment of the pH results in the binding of large quantities of proteins making polyelectrolyte brushes widely used as biointerfaces. However, the interaction between proteins and polyelectrolyte brushes remains poorly understood. Protein binding to brushes despite net repulsion indicates that the mechanism is determined by more than electrostatic effects. In this thesis polyelectrolyte brushes, and protein-polyelectrolyte interactions were characterized using new methods. The results show that non-electrostatic interactions play an important role in protein binding to pH-responsive polyelectrolyte brushes. Active switching of polyelectrolyte brushes requires control of the pH. However, controlled pH switching that is convenient and non-invasive has proven difficult to achieve. In this thesis electrochemistry was used to generate local pH gradients, that resulted in reversible switches of polyelectrolyte brushes, even in highly buffered liquids and in biological solutions like serum. Reversible electrochemical switching of polyelectrolyte brushes was accomplished by employing diazonium salt surface functionalization. Electrochemical switching was used to control protein-polyelectrolyte interactions to create polyelectrolyte brush electrodes that captured and released high quantities of proteins on-demand. Our method for electronic control of protein immobilization should increase the utility of pH-stimuli-responsive polymer brushes in applications such as bioanalytics, protein purification, and protein drug-delivery.
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6. |
- Dietrich, Franciele, et al.
(author)
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Effect of storage and preconditioning of healing rat Achilles tendon on structural and mechanical properties
- 2021
-
In: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 11:1
-
Journal article (peer-reviewed)abstract
- Tendon tissue storage and preconditioning are often used in biomechanical experiments and whether this generates alterations in tissue properties is essential to know. The effect of storage and preconditioning on dense connective tissues, like tendons, is fairly understood. However, healing tendons are unlike and contain a loose connective tissue. Therefore, we investigated if storage of healing tendons in the fridge or freezer changed the mechanical properties compared to fresh tendons, using a pull-to-failure or a creep test. Tissue morphology and cell viability were also evaluated. Additionally, two preconditioning levels were tested. Rats underwent Achilles tendon transection and were euthanized 12 days postoperatively. Statistical analyzes were done with one-way ANOVA or Student’s t-test. Tissue force and stress were unaltered by storage and preconditioning compared to fresh samples, while high preconditioning increased the stiffness and modulus (p ≤ 0.007). Furthermore, both storage conditions did not modify the viscoelastic properties of the healing tendon, but altered transverse area, gap length, and water content. Cell viability was reduced after freezing. In conclusion, preconditioning on healing tissues can introduce mechanical data bias when having extensive tissue strength diversity. Storage can be used before biomechanical testing if structural properties are measured on the day of testing.
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7. |
- Matthiesen, Isabelle, et al.
(author)
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Continuous Monitoring Reveals Protective Effects of N‐Acetylcysteine Amide on an Isogenic Microphysiological Model of the Neurovascular Unit
- 2021
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In: Small. - : Wiley. - 1613-6810 .- 1613-6829. ; 17:32, s. 2101785-
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Journal article (peer-reviewed)abstract
- Microphysiological systems mimic the in vivo cellular ensemble and microenvironment with the goal of providing more human-like models for biopharmaceutical research. In this study, the first such model of the blood-brain barrier (BBB-on-chip) featuring both isogenic human induced pluripotent stem cell (hiPSC)-derived cells and continuous barrier integrity monitoring with <2 min temporal resolution is reported. Its capabilities are showcased in the first microphysiological study of nitrosative stress and antioxidant prophylaxis. Relying on off-stoichiometry thiol–ene–epoxy (OSTE+) for fabrication greatly facilitates assembly and sensor integration compared to the prevalent polydimethylsiloxane devices. The integrated cell–substrate endothelial resistance monitoring allows for capturing the formation and breakdown of the BBB model, which consists of cocultured hiPSC-derived endothelial-like and astrocyte-like cells. Clear cellular disruption is observed when exposing the BBB-on-chip to the nitrosative stressor linsidomine, and the barrier permeability and barrier-protective effects of the antioxidant N-acetylcysteine amide are reported. Using metabolomic network analysis reveals further drug-induced changes consistent with prior literature regarding, e.g., cysteine and glutathione involvement. A model like this opens new possibilities for drug screening studies and personalized medicine, relying solely on isogenic human-derived cells and providing high-resolution temporal readouts that can help in pharmacodynamic studies.
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8. |
- Iseri, Emre
(author)
-
Microfluidic Compartmentalization for Smart Materials, Medical Diagnostics and Cell Therapy
- 2022
-
Doctoral thesis (other academic/artistic)abstract
- The organisation of fluids in small compartments is ubiquitous in nature, such as in the cellular composition of all life. This work explores several engineering avenues where microscale fluid compartmentalization can bring novel material properties or novel functionality in life sciences or medicine. Here, we introduce four unique compartmentalization methods: 1) 3D fluid self-organisation in microscaffolds (FLUID3EAMS), 2) 2D microcapillary arrays on a dipstick (Digital Dipstick), 3) a sliding microfluidic platform with cross-flow (Slip-X-Chip), and 4) compartmentalization by cutting of soft solid matter (Solidify & Cut). These methods were used in a wide range of applications. Within the area of smart materials, we applied FLUID3EAMS to synthesize materials with temperature-tuneable permeability and surface energy and to establish, in a well-controlled fashion, tissue-like materials in the form of 3D droplet interface bilayer networks. Solidify & Cut was used to form soft composites with a new type of magnetic behaviour, rotation-induced ferromagnetism, that allows easy reprogramming of the magnetization of magnetopolymers. Within the area of medical diagnostics, we applied Digital Dipstick to perform rapid digital bacterial culture in a dipstick format and obtained clinically relevant diagnostic results on samples from patients with a urinary tract infection. Furthermore, Slip-X-Chip enables particle concentration and washing as new functions in sliding microfluidic platforms, which significantly expands their potential application area. Finally, within the area of cell therapy, we explored the microencapsulation of high concentrations of therapeutic cells and presented a novel technique to fabricate core-shell microcapsules by exploiting the superior material properties of spider silk membranes.
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9. |
- Blust, Kelly
(author)
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Advancing 3D Cell Cultures of Stem-Cell Derived Pancreatic Islets and Breast Cancer Cells Using Recombinant Functionalized Spider Silk : Insights into cellular composition using bioinformatic methods
- 2024
-
Doctoral thesis (other academic/artistic)abstract
- The culture of cells in 3D creates a more physiologically relevant cell environment than conventional 2D cultures. Interactions of cells with the extracellular matrix induce important cellular signalling that regulates cell adhesion, migration, proliferation, differentiation, and survival. This is crucial for modelling cell development and disease. This thesis aims to develop and analyse improved 3D cell culture methods for stem cell-derived pancreatic islets (SC-islets) and breast cancer cell lines using a functionalized recombinant spider silk. Spider silk is a natural protein-based material with remarkable mechanical properties of high strength and elasticity. It is also biodegradable and cytocompatible. FN-silk, the recombinant spider silk protein utilized in this thesis, is functionalized with a cell binding motif (RGD) from fibronectin, to improve cell adhesion. Notably, FN-silk self-assembles at the liquid-air interface into a fibrillar structure, making it favourable as support for cell culture. In this thesis, bioinformatic methods were used to discover how the FN-silk supported environment affects the gene expression of cells and the cellular heterogeneity of SC-islets during a differentiation process. Additionally, bioinformatical analysis of the effect of 3D cell culture of breast cancer cell lines in FN-silk networks was performed. The first part of the thesis addresses serval challenges in pancreatic islet transplantation, by presenting an optimized protocol for pancreatic differentiation from human pluripotent stem cells, improving in vitro cultivation, and developing a cryopreservation method for SC-islets. The differentiation protocol presented in Paper 1 resulted in pure endocrine cell populations, avoiding unwanted proliferating and non-endocrine cells. It was also demonstrated that these SC-islets matured in vivo, and could effectively reverse diabetes in a diabetic mouse model. Single-cell RNA sequencing analysis provided new insights into the cellular composition and gene expression of the SC-islets before and after transplantation. In Paper 2, an innovative method for 3D in vitro cultivation of SC-islets using FN-silk networks mimicking the extracellular matrix was established. The FN-silk networks provided structural support for in vitro cultivation and handling during in vivo transplantation. The viability and functionality of free and FN-silk incorporated SC-islets were evaluated and compared. Single-cell RNA sequencing analyses confirmed maintenance of cellular composition, with a slightly improved beta cell maturation for SC-islets supported by FN-silk. In Paper 3, a novel strategy for cryopreservation of SC-islets was explored. The twisted vitrification method, previously employed for 2D cultures, was adapted for 3D cultures by utilizing integration into FN-silk networks to facilitate handling during the vitrification process. The second part of the thesis aimed to develop a method for 3D culture of breast cancer cells to better replicate the complexity of the tumour microenvironment. In Paper 4, FN-silk networks were used to generate a 3D environment for breast cancer cells where crucial cell-ECM interactions can be established. Proliferation rates and key marker expression of the cells cultured in 2D versus in the FN-silk network environment were investigated. Bioinformatic analysis of bulk RNA sequencing data was used to compare breast cancer cells in conventional 2D cell cultures with those cultured in 3D with the support of FNsilk. In conclusion, the work conducted in this thesis presents significant advancements in the development and analyses of 3D cell cultures of both SCislets and breast cancer cell lines, potentially enhancing therapeutic applications, disease modeling, and drug testing.
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10. |
- Johansson, Martin L, et al.
(author)
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Non-invasive sampling procedure revealing the molecular events at different abutments of bone-anchored hearing systems–A prospective clinical pilot study
- 2022
-
In: Frontiers in Neuroscience. - : Frontiers Media SA. - 1662-4548 .- 1662-453X. ; 16
-
Journal article (peer-reviewed)abstract
- Purpose: To investigate the molecular activities in different compartments around the bone-anchored hearing system (BAHS) with either electropolished or machined abutments and to correlate these activities with clinical and microbiological findings. Materials and methods: Twelve patients received machined or electropolished abutments after implant installation of BAHS. Peri-abutment fluid and tissue were collected from baseline to 12 months. Gene expression of cytokines and factors related to tissue healing and inflammation, regeneration and remodelling, as well as bacterial recognition were determined using quantitative-polymerase chain reaction (qPCR). The clinical status was evaluated using the Holgers scoring system, and bacterial colonisation was investigated by culturing. Results: The gene expression of inflammatory cytokines (IL-8, IL-1β, and IL-10) and bacteria-related Toll-like receptors (2 and 4) was higher in the peri-abutment fluid than at baseline and in the peri-abutment tissue at 3 and 12 months. Conversely, the expression of genes related to tissue regeneration (Coll1a1 and FOXO1) was higher in the tissue samples than in the peri-abutment fluid at 3 and 12 months. Electropolished abutments triggered higher expression of inflammatory cytokines (IL-8 and IL-1β) (in peri-abutment fluid) and regeneration factor FOXO1 (in peri-abutment tissue) than machined abutments. Several cytokine genes in the peri-abutment fluid correlated positively with the detection of aerobes, anaerobes and Staphylococcus species, as well as with high Holger scores. Conclusion: This study provides unprecedented molecular information on the biological processes of BAHS. Despite being apparently healed, the peri-abutment fluid harbours prolonged inflammatory activity in conjunction with the presence of different bacterial species. An electropolished abutment surface appears to be associated with stronger proinflammatory activity than that with a machined surface. The analysis of the peri-abutment fluid deserves further verification as a non-invasive sampling and diagnostic procedure of BAHS.
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11. |
- Hutchinson, Daniel, et al.
(author)
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Highly Customizable Bone Fracture Fixation through the Marriage of Composites and Screws
- 2021
-
In: Advanced Functional Materials. - : John Wiley and Sons Inc. - 1616-301X .- 1616-3028. ; 31:41
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Journal article (peer-reviewed)abstract
- Open reduction internal fixation (ORIF) metal plates provide exceptional support for unstable bone fractures; however, they often result in debilitating soft-tissue adhesions and their rigid shape cannot be easily customized by surgeons. In this work, a surgically feasible ORIF methodology, called AdhFix, is developed by combining screws with polymer/hydroxyapatite composites, which are applied and shaped in situ before being rapidly cured on demand via high-energy visible-light-induced thiol–ene coupling chemistry. The method is developed on porcine metacarpals with transverse and multifragmented fractures, resulting in strong and stable fixations with a bending rigidity of 0.28 (0.03) N m2 and a maximum load before break of 220 (15) N. Evaluations on human cadaver hands with proximal phalanx fractures show that AdhFix withstands the forces from finger flexing exercises, while short- and long-term in vivo rat femur fracture models show that AdhFix successfully supports bone healing without degradation, adverse effects, or soft-tissue adhesions. This procedure represents a radical new approach to fracture fixation, which grants surgeons unparalleled customizability and does not result in soft-tissue adhesions. © 2021 The Authors.
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12. |
- Muneer, Faraz, et al.
(author)
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Innovative Green Way to Design Biobased Electrospun Fibers from Wheat Gluten and These Fibers' Potential as Absorbents of Biofluids
- 2022
-
In: ACS Environmental Au. - : American Chemical Society (ACS). - 2694-2518. ; 2:3, s. 232-241
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Journal article (peer-reviewed)abstract
- In this study, a new method was developed to successfully design sustainable microfibers from wheat gluten proteins using a nonreducing solvent and electrospinning. We explored the morphology by X-ray tomography, scanning electron microscopy (SEM), and confocal laser scanning microscopy (CLSM), protein chemistry and cross-linking by size exclusion-high-performance liquid chromatography (SE-HPLC), and secondary structure by Fourier transform infrared spectroscopy (FT-IR) of fibers containing 15 and 20% of gluten. The impact of heat (130 °C) post-treatment on the polymerization properties of fibers and their absorption performance in different biofluids were also evaluated. The fibers with 20% gluten showed a uniform architecture supported by a relatively stronger fibrous network as compared to irregular and brittle fibers from 15% gluten. Heat treatment of fibers increased the protein cross-linking in all electrospun fibers as compared to the non-heat-treated fibers, as evidenced by SE-HPLC. An increase in the amount of α-helices and random coils was observed in the proteins of all of the heat-treated fibers compared to the nontreated fibers by FT-IR. This suggested that the heat treatment contributed positively to the gluten protein's chemical rearrangements, e.g., aggregation, new hydrogen and isopeptide bonding, and conversion of some of the sulfhydryl groups into disulfide cross-links, contributing positively to the functional performance. The heat-treated electrospun fibers with 20% gluten showed a very attractive blood absorption capacity (323%) and reasonable stability in phosphate-buffered saline (PBS) buffer compared to 15% gluten fibers and non-heat-treated fibers. Cotton-like fiber architecture, high blood absorption capacity, and reasonable stability in PBS buffer are properties desired for absorbents of biofluids and should be further explored in healthcare and medical applications.
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13. |
- Apelgren, Peter, et al.
(author)
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Vascularization of tissue engineered cartilage-Sequential in vivo MRI display functional blood circulation
- 2021
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In: Biomaterials. - : Elsevier BV. - 0142-9612 .- 1878-5905. ; 276
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Journal article (peer-reviewed)abstract
- Establishing functional circulation in bioengineered tissue after implantation is vital for the delivery of oxygen and nutrients to the cells. Native cartilage is avascular and thrives on diffusion, which in turn depends on proximity to circulation. Here, we investigate whether a gridded three-dimensional (3D) bioprinted construct would allow ingrowth of blood vessels and thus prove a functional concept for vascularization of bioengineered tissue. Twenty 10 x 10 x 3-mm 3Dbioprinted nanocellulose constructs containing human nasal chondrocytes or cell-free controls were subcutaneously implanted in 20 nude mice. Over the next 3 months, the mice were sequentially imaged with a 7 T small-animal MRI system, and the diffusion and perfusion parameters were analyzed. The chondrocytes survived and proliferated, and the shape of the constructs was well preserved. The diffusion coefficient was high and well preserved over time. The perfusion and diffusion patterns shown by MRI suggested that blood vessels develop over time in the 3D bioprinted constructs; the vessels were confirmed by histology and immunohistochemistry. We conclude that 3D bioprinted tissue with a gridded structure allows ingrowth of blood vessels and has the potential to be vascularized from the host. This is an essential step to take bioengineered tissue from the bench to clinical practice.
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14. |
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15. |
- Hansson, Magnus L., et al.
(author)
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Artificial spider silk supports and guides neurite extension in vitro
- 2021
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In: The FASEB Journal. - : John Wiley & Sons. - 0892-6638 .- 1530-6860. ; 35:11
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Journal article (peer-reviewed)abstract
- Surgical intervention with the use of autografts is considered the gold standard to treat peripheral nerve injuries. However, a biomaterial that supports and guides nerve growth would be an attractive alternative to overcome problems with limited availability, morbidity at the site of harvest, and nerve mismatches related to autografts. Native spider silk is a promising material for construction of nerve guidance conduit (NGC), as it enables regeneration of cm-long nerve injuries in sheep, but regulatory requirements for medical devices demand synthetic materials. Here, we use a recombinant spider silk protein (NT2RepCT) and a functionalized variant carrying a peptide derived from vitronectin (VN-NT2RepCT) as substrates for nerve growth support and neurite extension, using a dorsal root ganglion cell line, ND7/23. Two-dimensional coatings were benchmarked against poly-d-lysine and recombinant laminins. Both spider silk coatings performed as the control substrates with regards to proliferation, survival, and neurite growth. Furthermore, NT2RepCT and VN-NT2RepCT spun into continuous fibers in a biomimetic spinning set-up support cell survival, neurite growth, and guidance to an even larger extent than native spider silk. Thus, artificial spider silk is a promising biomaterial for development of NGCs.
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16. |
- Söderlund, Zackarias
(author)
-
Engineering the extracellular matrix to model diseases and orchestrate regeneration
- 2023
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Doctoral thesis (other academic/artistic)abstract
- The extracellular matrix is not only a scaffold to which cells attach, but it is also a matrix that communicates cell signals. Because of the interplay between cells and the extracellular matrix, changes in the extracellular matrix can steer cell fate. This opens up the opportunity to design and engineer the extracellular matrix to communicate changes to the cells. Thus, this thesis has focused on understanding which parameters and signals influence cells, but also on how to utilise this knowledge to engineer a completely defined extracellular matrix. The extracellular matrix can be modulated in several ways, such as cell attachment, degradation properties, porosity, stiffness as well as being easily functionalised with molecules of interest using click chemistry.Two of the papers in this thesis focus on the development of new tools for glycosaminoglycan research to get a better understanding of how this can be modulated to steer cell signalling. Glycosaminoglycans bind growth factors, which can then either act as a co-receptor to increase the potency of the growth factor or to protect the growth factors from being broken down or inactivated. The tools that we have developed open the possibility to better study the production of glycosaminoglycans from different types of cells and better understand what changes occur in glycosaminoglycan synthesis during disease.The second two papers in this thesis focus on understanding the extracellular matrix. Article number one focuses on the effect of different extracellular matrices and stretch on cells and their secretome. Article number two, which has been the focus of this thesis, utilises the new findings in the other articles about glycosaminoglycans and the extracellular matrix to create a synthetic and defined extracellular matrix. This extracellular matrix is modified with glycosaminoglycans to have a slow release of growth factors to instruct cells to differentiate both in vitro and in vivo.
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17. |
- de Oliveira Barud, Hélida Gomes, et al.
(author)
-
Bacterial Nanocellulose in Dentistry: Perspectives and Challenges
- 2021
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In: Molecules. - : MDPI AG. - 1420-3049 .- 1420-3049. ; 26:1
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Research review (peer-reviewed)abstract
- Bacterial cellulose (BC) is a natural polymer that has fascinating attributes, such as biocompatibility, low cost, and ease of processing, being considered a very interesting biomaterial due to its options for moldability and combination. Thus, BC-based compounds (for example, BC/collagen, BC/gelatin, BC/fibroin, BC/chitosan, etc.) have improved properties and/or functionality, allowing for various biomedical applications, such as artificial blood vessels and microvessels, artificial skin, and wounds dressing among others. Despite the wide applicability in biomedicine and tissue engineering, there is a lack of updated scientific reports on applications related to dentistry, since BC has great potential for this. It has been used mainly in the regeneration of periodontal tissue, surgical dressings, intraoral wounds, and also in the regeneration of pulp tissue. This review describes the properties and advantages of some BC studies focused on dental and oral applications, including the design of implants, scaffolds, and wound-dressing materials, as well as carriers for drug delivery in dentistry. Aligned to the current trends and biotechnology evolutions, BC-based nanocomposites offer a great field to be explored and other novel features can be expected in relation to oral and bone tissue repair in the near future.
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18. |
- Lin, CH, et al.
(author)
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In Vitro Study of Human Immune Responses to Hyaluronic Acid Hydrogels, Recombinant Spidroins and Human Neural Progenitor Cells of Relevance to Spinal Cord Injury Repair
- 2021
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In: Cells. - : MDPI AG. - 2073-4409. ; 10:7
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Journal article (peer-reviewed)abstract
- Scaffolds of recombinant spider silk protein (spidroin) and hyaluronic acid (HA) hydrogel hold promise in combination with cell therapy for spinal cord injury. However, little is known concerning the human immune response to these biomaterials and grafted human neural stem/progenitor cells (hNPCs). Here, we analyzed short- and long-term in vitro activation of immune cells in human peripheral blood mononuclear cells (hPBMCs) cultured with/without recombinant spidroins, HA hydrogels, and/or allogeneic hNPCs to assess potential host–donor interactions. Viability, proliferation and phenotype of hPBMCs were analyzed using NucleoCounter and flow cytometry. hPBMC viability was confirmed after exposure to the different biomaterials. Short-term (15 h) co-cultures of hPBMCs with spidroins, but not with HA hydrogel, resulted in a significant increase in the proportion of activated CD69+ CD4+ T cells, CD8+ T cells, B cells and NK cells, which likely was caused by residual endotoxins from the Escherichia coli expression system. The observed spidroin-induced hPBMC activation was not altered by hNPCs. It is resource-effective to evaluate human compatibility of novel biomaterials early in development of the production process to, when necessary, make alterations to minimize rejection risk. Here, we present a method to evaluate biomaterials and hPBMC compatibility in conjunction with allogeneic human cells.
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19. |
- Svensson, Fredric G., et al.
(author)
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Hemocompatibility of Nanotitania-Nanocellulose Hybrid Materials
- 2021
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In: Nanomaterials. - : MDPI. - 2079-4991. ; 11:5
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Journal article (peer-reviewed)abstract
- In order to develop a new type of improved wound dressing, we combined the wound healing properties of nanotitania with the advantageous dressing properties of nanocellulose to create three different hybrid materials. The hemocompatibility of the synthesized hybrid materials was evaluated in an in vitro human whole blood model. To our knowledge, this is the first study of the molecular interaction between hybrid nanotitania and blood proteins. Two of the hybrid materials prepared with 3 nm colloidal titania and 10 nm hydrothermally synthesized titania induced strong coagulation and platelet activation but negligible complement activation. Hence, they have great potential as a new dressing for promoting wound healing. Unlike the other two, the third hybrid material using molecular ammonium oxo-lactato titanate as a titania source inhibited platelet consumption, TAT generation, and complement activation, apparently via lowered pH at the surface interface. It is therefore suitable for applications where a passivating surface is desired, such as drug delivery systems and extracorporeal circuits. This opens the possibility for a tailored blood response through the surface functionalization of titania.
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20. |
- Beygelzimer, Yan, et al.
(author)
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Geometry of plastic deformation in metals as piecewise isometric transformations
- 2024
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In: Scientific Reports. - 2045-2322. ; 14:1
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Journal article (peer-reviewed)abstract
- Deformation mechanisms of crystalline solids has been the subject of research for more than two centuries. The theory of dislocations dominates modern views but still has significant gaps demanding the introduction of additional concepts for the coherent quantitative description of physical phenomena. In this work, we propose a coherent geometric description of motion and deformation in crystalline solids as piecewise isometric transformations (PWIT). The latter only includes operations that, similar to interatomic spacing in crystalline lattice, do not alter distances between reference points, i.e. translations, rotations and mirror reflections. The difference between solid-body translations and plastic deformations is that the isometric transformations have discontinuities that in real-life materials realise through dislocations (termination of shifts), disclinations (termination of rotations), and twins (mirror reflections). The conceptual description of plastic deformations as PWIT can be useful for the better description of physical phenomena, proposing new hypothesis, and for developing predictive analytical models. In this paper, the use of this conceptual description enables proposing new hypothesis about the nature of such interesting phenomena in severe plastic deformation as (i) stationary ‘solid state turbulence’ stage in high pressure torsion, and (ii) rate of mass transfer (mechanically assisted diffusion) in simple-shear deformation.
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21. |
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22. |
- Pettersen, Emily, 1996, et al.
(author)
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Electrical stimulation to promote osseointegration of bone anchoring implants: a topical review
- 2022
-
In: Journal of Neuroengineering and Rehabilitation. - : Springer Science and Business Media LLC. - 1743-0003. ; 19:1
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Journal article (peer-reviewed)abstract
- Electrical stimulation has shown to be a promising approach for promoting osseointegration in bone anchoring implants, where osseointegration defines the biological bonding between the implant surface and bone tissue. Bone-anchored implants are used in the rehabilitation of hearing and limb loss, and extensively in edentulous patients. Inadequate osseointegration is one of the major factors of implant failure that could be prevented by accelerating or enhancing the osseointegration process by artificial means. In this article, we reviewed the efforts to enhance the biofunctionality at the bone-implant interface with electrical stimulation using the implant as an electrode. We reviewed articles describing different electrode configurations, power sources, and waveform-dependent stimulation parameters tested in various in vitro and in vivo models. In total 55 English-language and peer-reviewed publications were identified until April 2020 using PubMed, Google Scholar, and the Chalmers University of Technology Library discovery system using the keywords: osseointegration, electrical stimulation, direct current and titanium implant. Thirteen of those publications were within the scope of this review. We reviewed and compared studies from the last 45 years and found nonuniform protocols with disparities in cell type and animal model, implant location, experimental timeline, implant material, evaluation assays, and type of electrical stimulation. The reporting of stimulation parameters was also found to be inconsistent and incomplete throughout the literature. Studies using in vitro models showed that osteoblasts were sensitive to the magnitude of the electric field and duration of exposure, and such variables similarly affected bone quantity around implants in in vivo investigations. Most studies showed benefits of electrical stimulation in the underlying processes leading to osseointegration, and therefore we found the idea of promoting osseointegration by using electric fields to be supported by the available evidence. However, such an effect has not been demonstrated conclusively nor optimally in humans. We found that optimal stimulation parameters have not been thoroughly investigated and this remains an important step towards the clinical translation of this concept. In addition, there is a need for reporting standards to enable meta-analysis for evidence-based treatments.
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23. |
- Albrektsson, Tomas, 1945, et al.
(author)
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An Imbalance of the Immune System Instead of a Disease Behind Marginal Bone Loss Around Oral Implants: Position Paper
- 2020
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In: The International journal of oral & maxillofacial implants. - : Quintessence Publishing. - 1942-4434 .- 0882-2786. ; 35:3, s. 495-502
-
Journal article (peer-reviewed)abstract
- PURPOSE: The purpose of this paper is to present evidence that supports the notion that the primary reason behind marginal bone loss and implant failure is immune-based and that bacterial actions in the great majority of problematic cases are of a secondary nature. MATERIALS AND METHODS: The paper is written as a narrative review. RESULTS: Evidence is presented that commercially pure titanium is not biologically inert, but instead activates the innate immune system of the body. For its function, the clinical implant is dependent on an immune/inflammatory defense against bacteria. Biologic models such as ligature studies have incorrectly assumed that the primary response causing marginal bone loss is due to bacterial action. In reality, bacterial actions are secondary to an imbalance of the innate immune system caused by the combination of titanium implants and ligatures, ie, nonself. This immunologic imbalance may lead to marginal bone resorption even in the absence of bacteria. CONCLUSION: Marginal bone loss and imminent oral implant failure cannot be properly analyzed without a clear understanding of immunologically caused tissue responses.
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24. |
- Khati, Vamakshi, 1991-
(author)
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Decellularized liver extracellular matrix as a 3D scaffold for bioengineering applications
- 2022
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Doctoral thesis (other academic/artistic)abstract
- The increasing global burden of end-stage liver disease has increased the need for liver transplantation, the definitive cure. However, there is a huge discrepancy between the number of available organ donors and the number of patients waiting for transplantation, resulting in the deaths of a significant number of patients on the waiting list as only 10% of the global need for transplantation is met. Liver tissue engineering is a promising alternative solution to this problem, which utilizes bioengineering techniques to create an ex vivo microenvironment niche for liver cells embedded in a liver-specific extracellular matrix (ECM) for cell growth and function. Despite many advances in this field, the scarcity of appropriate ECM-mimicking biomaterials with good mechanical properties for biofabrication technique remains limited. To address this, different biofabrication techniques, such as bioprinting and biomaterial scaffolds, are studied to simulate liver microarchitecture for different applications. This thesis presents the development and application of a decellularized liver extracellular matrix hydrogel combined with the liver cell line HepG2 (papers 1-3). It also focuses on the decellularized whole liver scaffold to differentiate amniotic epithelial cells (paper 4). The decellularized liver extracellular matrix (dLM) is a cell-free scaffold that retains liver-specific components to direct cell growth and functions. The dLM can be digested to form hydrogel for 3D bioprinting applications, or it can be used as a biomaterial scaffold to seed the cells directly. In paper I, porcine dLM hydrogel was modified with gelatin and a PEG-based crosslinker to induce a cytocompatible gelation mechanism to generate a robust bioink with a 16-fold increment in viscosity and a 32-fold increment in storage modulus as compared to unmodified dLM hydrogel. This work established the application of dLM with other biofabrication methods, such as Indirect bioprinting, where a sacrificial biopolymer is 3D printed, and the scaffold material is subsequently added. In paper II, a 3D-printed polyvinyl alcohol framework resembling the liver lobules was used as a sacrificial scaffold to impart its structure to the dLM hydrogel modified with PEG-based crosslinker and mushroom tyrosinase. The crosslinked dLM hydrogel with co-culture of HepG2 and NIH 3T3 fibroblasts cell line retained the structure of PVA to create a scaled-up liver-like microarchitecture with lobules. The PVA dissolved with cell culture media leaving behind a robust 3D construct of dLM hydrogel. In paper III, cellulose nanofibril-coated HepG2 spheroids incorporating dLM hydrogel were studied for tumor modeling. The dLM incorporation affected the spheroid formation and growth depending on the time of addition. In paper IV, the functional differentiation of amniotic epithelial cells into hepatocyte-like cells was performed in a decellularized rat liver scaffold in a perfusion bioreactor with dynamic oxygenation and media exchange. This dLM perfusion technology supported the maturation and proliferation of amniotic epithelial cells into hepatocyte-like cells. This is a preliminary step into developing a liver-like organ model in a laboratory setting. To conclude, this thesis presents different bioengineering approaches, such as 3D bioprinting and perfusion decellularization, to study the 3D dLM scaffolds for HepG2 and amniotic epithelial cell culture. 3D bioprinting technique utilized a robust dLM hydrogel to create a scaled-up microarchitecture, whereas perfusion decellularization retained the natural 3D architecture of the whole liver ECM and the native vascular system for recellularizing the scaffold with stem cells. We successfully modified and characterized the dLM hydrogel to enhance its printability to develop complex structures such as liver lobules and microchannels. We utilized different cell systems, including monoculture, co-culture, and spheroids, to analyze the biocompatibility, cell proliferation, and liver-specific functions of the dLM scaffold. Ultimately, the advancement of dLM as a biomaterial presented in this thesis could improve the application and modification of various decellularized tissues to generate larger-scale models for in vitro testing and organ transplantation.
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25. |
- Baş, Yağmur, et al.
(author)
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Preparation and Characterization of Softwood and Hardwood Nanofibril Hydrogels: Toward Wound Dressing Applications
- 2023
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In: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 24:12, s. 5605-5619
-
Journal article (peer-reviewed)abstract
- Hydrogels of cellulose nanofibrils (CNFs) are promising wound dressing candidates due to their biocompatibility, high water absorption, and transparency. Herein, two different commercially available wood species, softwood and hardwood, were subjected to TEMPO-mediated oxidation to proceed with delignification and oxidation in a one-pot process, and thereafter, nanofibrils were isolated using a high-pressure microfluidizer. Furthermore, transparent nanofibril hydrogel networks were prepared by vacuum filtration. Nanofibril properties and network performance correlated with oxidation were investigated and compared with commercially available TEMPO-oxidized pulp nanofibrils and their networks. Softwood nanofibril hydrogel networks exhibited the best mechanical properties, and in vitro toxicological risk assessment showed no detrimental effect for any of the studied hydrogels on human fibroblast or keratinocyte cells. This study demonstrates a straightforward processing route for direct oxidation of different wood species to obtain nanofibril hydrogels for potential use as wound dressings, with softwood having the most potential.
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26. |
- Eriksson, Gustav, 1994
(author)
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Atom Probe Tomography Investigations of Biologically Relevant Nanoparticles
- 2022
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Licentiate thesis (other academic/artistic)abstract
- The study of materials at the nanoscale is essential in many scientific disciplines. For example, in materials science the size of the building blocks of a material is directly linked to its properties. New materials are constantly being developed having features at the nanoscale, for example nanoparticles that are used in fields such as catalysis, electronics, and medicine. In biology, many features exist which have nanosized structures including proteins. The 3D secondary structure of proteins is directly linked to their functions; hence structure determination of proteins is of high interest to gain information of biological processes that serves the development of future medicines. Due to the importance of nanostructures, many methods for their investigation have been developed such as X-ray diffraction, electron microscopy, and atom probe tomography. These methods rely on different probes and are thus often considered complementary as they provide different information. For the same reason, they put different constraints or limitations on the materials studied. In this work, two novel methods for studying nanoparticles of biological relevance, gold nanoparticles and hydroxyapatite nanoparticles, have been developed for analysis using atom probe tomography. Gold nanoparticles are popularly used as markers for biomolecules and to immobilize biomolecules on surfaces with retained function and activity. Several methods have been developed in the last decade to study nanoparticles using atom probe tomography, generally involving forming a metal matrix embedding the particles in a material from which a specimen can be made. In this thesis, an alternative approach utilizing a silica matrix made by a sol-gel method used to embed a gold nanoparticle covered surface is presented. This silica-based method provides an environment for the particles that is similar to an aqueous environment. Nanoparticles of hydroxyapatite, a mineral that is found in bone and teeth, are commonly used as biomaterials, for example as coatings to improve the performance of surgical implants. In this thesis, hydroxyapatite nanoparticles immobilized onto titanium are examined. The analysed surfaces were sputter coated with chromium, forming a matrix that allows for correlative transmission electron microscopy and atom probe tomography analysis. It is shown that calcium and phosphorous integrated into the surface oxide of the titanium, revealing detailed insights on immobilization of the nanoparticles on the surface. This integration resembles the osseointegration of bone when compared to similar titanium implants being introduced to the human body.
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27. |
- Pettersen, Emily, 1996, et al.
(author)
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Enhancing osteoblast survival through pulsed electrical stimulation and implications for osseointegration
- 2021
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In: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 11:1
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Journal article (peer-reviewed)abstract
- Electrical stimulation has been suggested as a means for promoting the direct structural and functional bonding of bone tissue to an artificial implant, known as osseointegration. Previous work has investigated the impact of electrical stimulation in different models, both in vitro and in vivo, using various electrode configurations for inducing an electric field with a wide range of stimulation parameters. However, there is no consensus on optimal electrode configuration nor stimulation parameters. Here, we investigated a novel approach of delivering electrical stimulation to a titanium implant using parameters clinically tested in a different application, namely peripheral nerve stimulation. We propose an in vitro model comprising of Ti6Al4V implants precultured with MC3T3-E1 preosteoblasts, stimulated for 72 h at two different pulse amplitudes (10 mu A and 20 mu A) and at two different frequencies (50 Hz and 100 Hz). We found that asymmetric charge-balanced pulsed electrical stimulation improved cell survival and collagen production in a dose-dependent manner. Our findings suggest that pulsed electrical stimulation with characteristics similar to peripheral nerve stimulation has the potential to improve cell survival and may provide a promising approach to improve peri-implant bone healing, particularly to neuromusculoskeletal interfaces in which implanted electrodes are readily available.
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28. |
- Siwale, Workson, et al.
(author)
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Influence on off-gassing during storage of Scots pine wood pellets produced from sawdust with different extractive contents
- 2022
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In: Biomass and Bioenergy. - : Elsevier. - 0961-9534 .- 1873-2909. ; 156
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Journal article (peer-reviewed)abstract
- Off-gassing and self-heating are the major challenges when it comes to transportation and storage of wood pellets. The heat generated due to self-heating poses a fire risk while off-gassing of toxic gasses such as carbon monoxide (CO) and some volatile organic compounds (VOCs) is an environmental and human health risk. With the increase in production volumes of wood pellets which has subsequently increased the amounts of wood pellets in transportation and storage, there is need to find lasting solutions to off-gassing and self-heating of wood pellets. The objective of this study was to test the off-gassing abilities of Scots pine wood pellets produced from sawdust with varying amounts of extractives. The aim is to come up with raw material pre-treatment measures so as to produce wood pellets that are not liable to off-gassing. Six (6) types of sawdust raw materials namely; fresh pine sawdust (FPS), stored pine sawdust (SPS), sawdust plus pine rosin (PRS), sawdust plus linseed oil (LOS), sawdust plus tall oil (TOS) and acetone extracted sawdust (AES) were used to produce the pellets. The produced pellets were then subjected to off-gassing tests under controlled conditions using the ECOM J2KN analyser. The concentrations of carbon monoxide, carbon dioxide and methane increased with storage time but slowed down towards the end of the nine days test period. The formation of these gasses were largely dependent on the type of extractives present in the raw material and not the total extractive content. The formation of methane started later than the other gases and coincided with the time when residual oxygen was depleted.
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29. |
- Du, Xiaoyu, et al.
(author)
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Fabrication and characterization of sodium alginate-silicon nitride-PVA composite biomaterials with damping properties
- 2024
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In: Journal of The Mechanical Behavior of Biomedical Materials. - : Elsevier. - 1751-6161 .- 1878-0180. ; 155
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Journal article (peer-reviewed)abstract
- Silicon nitride is utilized clinically as a bioceramic for spinal fusion cages, owing to its high strength, osteoconductivity, and antibacterial effects. Nevertheless, silicon nitride exhibits suboptimal damping properties, a critical factor in mitigating traumatic bone injuries and fractures. In fact, there is a scarcity of spinal implants that simultaneously demonstrate proficient damping performance and support osteogenesis. In our study, we fabricated a novel sodium alginate-silicon nitride/poly(vinyl alcohol) (SA-SiN/PVA) composite scaffold, enabling enhanced energy absorption and rapid elastic recovery under quasi-static and impact loading scenarios. Furthermore, the study demonstrated that the incorporation of physical and chemical cross-linking significantly improved stiffness and recoverable energy dissipation. Concerning the interaction between cells and materials, our findings suggest that the addition of silicon nitride stimulated osteogenic differentiation while inhibiting Staphylococcus aureus growth. Collectively, the amalgamation of ceramics and tough hydrogels facilitates the development of advanced composites for spinal implants, manifesting superior damping, osteogenic potential, and antibacterial properties. This approach holds broader implications for applications in bone tissue engineering.
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30. |
- Franco Tabares, Sebastian, et al.
(author)
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Effect of airborne-particle abrasion and polishing on novel translucent zirconias: Surface morphology, phase transformation and insights into bonding
- 2021
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In: Journal of Prosthodontic Research. - : Japan Prosthodontic Society. - 1883-1958 .- 2212-4632. ; 65:1, s. 97-105
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Journal article (peer-reviewed)abstract
- Purpose: The purpose this study was to investigate the effect of Kern ' s air-borne particle abrasion protocol (KAPA) and polishing on two translucent zirconias (4Y, 5Y-zirconias) compared to a traditional zirconia (3Y-zirconia). Methods: Two different surface treatments were analysed by X-ray diffraction (XRD) and interferometry 1) KAPA (0.1 MPa, 50 mu m alumina, 10-12 mm distance, 15 sec and 30 sec and cleaning in ultrasound using isopropyl alcohol 99%) and 2) Clinical-delivery polishing paste (Zircon Brite, Dental Ventures, USA). Shear-bond strength tests (SBS's) were performed with a highly polished and virtually flat surface in combination with a 10-MDP based cement and a surface modified by KAPA in combination with zinc phosphate cement. The SBS was expressed in terms of MPa. Results: The mean values for monoclinic content were 13 wt%, 7 wt% and 2 wt% for 3Y-, 4Y- and 5Y-zirconias respectively, no differences were found between 15 and 30 seconds. Polishing did not result in phase transformation to monoclinic phase in any of the zirconias. The rhombohedral phase was identified in all types of zirconias regardless of surface treatment. Shear-bond strength tests showed 5 MPa for polished/10-MDP based cement and 3 MPa for KAPA/Zinc phosphate. Statistically significant differences were found between the two different surface treatments but not between the types of zirconias. Conclusions: KAPA for 15 sec seems to be equal to 30 sec regarding morphology and phase transformation. Sole micro-retention appears not to be fully responsible for the bonding phenomena of 10-MDP and zirconia that underwent KAPA.
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31. |
- Pandit, Santosh, 1987, et al.
(author)
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Sustained release of usnic acid from graphene coatings ensures long term antibiofilm protection
- 2021
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In: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322 .- 2045-2322. ; 11:1
-
Journal article (peer-reviewed)abstract
- Protecting surfaces from bacterial colonization and biofilm development is an important challenge for the medical sector, particularly when it comes to biomedical devices and implants that spend longer periods in contact with the human body. A particularly difficult challenge is ensuring long-term protection, which is usually attempted by ensuring sustained release of antibacterial compounds loaded onto various coatings. Graphene have a considerable potential to reversibly interact water insoluble molecules, which makes them promising cargo systems for sustained release of such compounds. In this study, we developed graphene coatings that act as carriers capable of sustained release of usnic acid (UA), and hence enable long-term protection of surfaces against colonization by bacterial pathogens Staphylococcus aureus and Staphylococcus epidermidis. Our coatings exhibited several features that made them particularly effective for antibiofilm protection: (i) UA was successfully integrated with the graphene material, (ii) a steady release of UA was documented, (iii) steady UA release ensured strong inhibition of bacterial biofilm formation. Interestingly, even after the initial burst release of UA, the second phase of steady release was sufficient to block bacterial colonization. Based on these results, we propose that graphene coatings loaded with UA can serve as effective antibiofilm protection of biomedical surfaces.
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32. |
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33. |
- Rampersadh, Claire, et al.
(author)
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Factors affecting the numerical response and fracture location of the GHBMC M50 rib in dynamic anterior-posterior loading
- 2022
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In: Journal of the Mechanical Behavior of Biomedical Materials. - : Elsevier BV. - 1751-6161 .- 1878-0180. ; 136
-
Journal article (peer-reviewed)abstract
- Rib fractures are common traumatic injuries, with links to increased morbidity and mortality. Finite element ribs from human body models have struggled to predict the force-displacement response, force and displacement at fracture, and the fracture location for isolated rib tests. In the current study, the sensitivity of a human body model rib with updated anisotropic and asymmetric material models to changes in boundary conditions, material properties, and geometry was investigated systematically to quantify contributions to response. The updated material models using uncalibrated average material properties from literature improved the force-displacement response of the model, whereas the cross-sectional geometry was the only parameter to effect fracture location. The resulting uncalibrated model with improved material models and cross-sectional geometry closely predicted experimental average force-displacement response and fracture location.
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34. |
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35. |
- Li, Tianzhong, et al.
(author)
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Material-based engineering of bacteria for cancer diagnosis and therapy
- 2021
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In: Applied Materials Today. - : Elsevier. - 2352-9407. ; 25
-
Journal article (peer-reviewed)abstract
- Various categories of biomaterials have been utilized for drug delivery, genetic modification, photodynamic and photothermal therapies due to their distinct physicochemical properties, including photothermal convertibility, stimuli-responsiveness, and inherent capability to generate photodynamical radicals. However, successful treatments of cancer are largely hindered by the limited accessibility of nanomaterials into hypoxic or metastatic tumor tissues. Among the various tumor-targeting strategies, bacterial fabrication exhibits particular advantages such as specific hypoxia tropism, high motility, and rapid self replication. Biomineralization, i.e. bacterial modification, involves the fabrication of bacteria by nanomaterials for precise cancer imaging as well as targeted drug delivery, overcoming the physiological barriers and improving the therapeutic efficiency. Fabrication of bacteria strains can be conducted by various methods, including direct adsorption, electrostatic interaction, covalent ligation, and surface precipitation. In this review, a brief introduction to commonly-utilized biomaterials and bacteria species is provided. A systemic overview of recent advances of bacteria fabrication strategies and techniques are then discussed, followed by future prospective of bacteria-facilitated cancer therapy and diagnostics.
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36. |
- Yuan, Hongbo, et al.
(author)
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Synthetic fibrous hydrogels as a platform to decipher cell–matrix mechanical interactions
- 2023
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In: Proceedings of the National Academy of Sciences of the United States of America. - 0027-8424. ; 120:15
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Journal article (peer-reviewed)abstract
- Cells continuously sense external forces from their microenvironment, the extracellular matrix (ECM). In turn, they generate contractile forces, which stiffen and remodel this matrix. Although this bidirectional mechanical exchange is crucial for many cell functions, it remains poorly understood. Key challenges are that the majority of available matrices for such studies, either natural or synthetic, are difficult to control or lack biological relevance. Here, we use a synthetic, yet highly biomimetic hydrogel based on polyisocyanide (PIC) polymers to investigate the effects of the fibrous architecture and the nonlinear mechanics on cell–matrix interactions. Live-cell rheology was combined with advanced microscopy-based approaches to understand the mechanisms behind cell-induced matrix stiffening and plastic remodeling. We demonstrate how cell-mediated fiber remodeling and the propagation of fiber displacements are modulated by adjusting the biological and mechanical properties of this material. Moreover, we validate the biological relevance of our results by demonstrating that cellular tractions in PIC gels develop analogously to those in the natural ECM. This study highlights the potential of PIC gels to disentangle complex bidirectional cell–matrix interactions and to improve the design of materials for mechanobiology studies.
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37. |
- Tommasini, Giuseppina, et al.
(author)
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Seamless integration of bioelectronic interface in an animal model via in vivo polymerization of conjugated oligomers
- 2022
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In: Bioactive Materials. - : Elsevier BV. - 2452-199X. ; 10, s. 107-116
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Journal article (peer-reviewed)abstract
- Leveraging the biocatalytic machinery of living organisms for fabricating functional bioelectronic interfaces, in vivo, defines a new class of micro-biohybrids enabling the seamless integration of technology with living biological systems. Previously, we have demonstrated the in vivo polymerization of conjugated oligomers forming conductors within the structures of plants. Here, we expand this concept by reporting that Hydra, an invertebrate animal, polymerizes the conjugated oligomer ETE-S both within cells that expresses peroxidase activity and within the adhesive material that is secreted to promote underwater surface adhesion. The resulting conjugated polymer forms electronically conducting and electrochemically active μm-sized domains, which are inter-connected resulting in percolative conduction pathways extending beyond 100 μm, that are fully integrated within the Hydra tissue and the secreted mucus. Furthermore, the introduction and in vivo polymerization of ETE-S can be used as a biochemical marker to follow the dynamics of Hydra budding (reproduction) and regeneration. This work paves the way for well-defined self-organized electronics in animal tissue to modulate biological functions and in vivo biofabrication of hybrid functional materials and devices.
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38. |
- Berglin, Mattias, 1970, et al.
(author)
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Flexible and Biocompatible Antifouling Polyurethane Surfaces Incorporating Tethered Antimicrobial Peptides through Click Reactions
- 2024
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In: Macromolecular Bioscience. - : John Wiley and Sons Inc. - 1616-5187 .- 1616-5195. ; 24:4
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Journal article (peer-reviewed)abstract
- Efficient, simple antibacterial materials to combat implant-associated infections are much in demand. Herein, the development of polyurethanes, both cross-linked thermoset and flexible and versatile thermoplastic, suitable for “click on demand” attachment of antibacterial compounds enabled via incorporation of an alkyne-containing diol monomer in the polymer backbone, is described. By employing different polyolic polytetrahydrofurans, isocyanates, and chain extenders, a robust and flexible material comparable to commercial thermoplastic polyurethane is prepared. A series of short synthetic antimicrobial peptides are designed, synthesized, and covalently attached in a single coupling step to generate a homogenous coating. The lead material is shown to be biocompatible and does not display any toxicity against either mouse fibroblasts or reconstructed human epidermis according to ISO and OECD guidelines. The repelling performance of the peptide-coated materials is illustrated against colonization and biofilm formation by Staphylococcus aureus and Staphylococcus epidermidis on coated plastic films and finally, on coated commercial central venous catheters employing LIVE/DEAD staining, confocal laser scanning microscopy, and bacterial counts. This study presents the successful development of a versatile and scalable polyurethane with the potential for use in the medical field to reduce the impact of bacterial biofilms.
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39. |
- Kamada, Ayaka, et al.
(author)
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Hierarchical propagation of structural features in protein nanomaterials
- 2022
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In: Nanoscale. - : Royal Society of Chemistry (RSC). - 2040-3372 .- 2040-3364. ; 14:6, s. 2502-2510
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Journal article (peer-reviewed)abstract
- Natural high-performance materials have inspired the exploration of novel materials from protein building blocks. The ability of proteins to self-organize into amyloid-like nanofibrils has opened an avenue to new materials by hierarchical assembly processes. As the mechanisms by which proteins form nanofibrils are becoming clear, the challenge now is to understand how the nanofibrils can be designed to form larger structures with defined order. We here report the spontaneous and reproducible formation of ordered microstructure in solution cast films from whey protein nanofibrils. The structural features are directly connected to the nanostructure of the protein fibrils, which is itself determined by the molecular structure of the building blocks. Hence, a hierarchical assembly process ranging over more than six orders of magnitude in size is described. The fibril length distribution is found to be the main determinant of the microstructure and the assembly process originates in restricted capillary flow induced by the solvent evaporation. We demonstrate that the structural features can be switched on and off by controlling the length distribution or the evaporation rate without losing the functional properties of the protein nanofibrils.
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40. |
- Mianehrow, Hanieh, et al.
(author)
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Strong reinforcement effects in 2D cellulose nanofibril-graphene oxide (CNF-GO) nanocomposites due to GO-induced CNF ordering
- 2020
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In: Journal of Materials Chemistry A. - : Royal Society of Chemistry (RSC). - 2050-7496 .- 2050-7488. ; 8:34, s. 17608-17620
-
Journal article (peer-reviewed)abstract
- Nanocomposites from native cellulose with low 2D nanoplatelet content are of interest as sustainable materials combining functional and structural performance. Cellulose nanofibril-graphene oxide (CNF-GO) nanocomposite films are prepared by a physical mixing-drying method, with a focus on low GO content, the use of very large GO platelets (2-45 mu m) and nanostructural characterization using synchrotron X-ray source for WAXS and SAXS. These nanocomposites can be used as transparent coatings, strong films or membranes, as gas barriers or in laminated form. CNF nanofibrils with random in-plane orientation, form a continuous non-porous matrix with GO platelets oriented in-plane. GO reinforcement mechanisms in CNF are investigated, and relationships between nanostructure and suspension rheology, mechanical properties, optical transmittance and oxygen barrier properties are investigated as a function of GO content. A much higher modulus reinforcement efficiency is observed than in previous polymer-GO studies. The absolute values for modulus and ultimate strength are as high as 17 GPa and 250 MPa at a GO content as small as 0.07 vol%. The remarkable reinforcement efficiency is due to improved organization of the CNF matrix; and this GO-induced mechanism is of general interest for nanostructural tailoring of CNF-2D nanoplatelet composites.
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41. |
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42. |
- Spiegelburg, Doreen Tabea, et al.
(author)
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Impact of surface coating and systemic anticoagulants on hemostasis and inflammation in a human whole blood model
- 2023
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In: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 18:1
-
Journal article (peer-reviewed)abstract
- BackgroundSurface compatibility with blood is critical both for scientific investigations on hemostasis and clinical applications. Regarding in vitro and ex vivo investigations, minimal alteration in physiological hemostasis is of particular importance to draw reliable conclusions on the human coagulation system. At the same time, artificial coagulation activation must be avoided, which is relevant for the patient, for example to prevent stent graft occlusion. The aim was to evaluate the advantages and disadvantages of antithrombotic and antifouling surface coatings in the context of their suitability for ex vivo incubation and the study of coagulation properties. MethodsWe investigated the impact of different protocols for surface coating of synthetic material and different anticoagulants on hemostasis and platelet activation in ex vivo human whole blood.Blood samples from healthy donors were incubated in coated microtubes on a rotating wheel at 37 degrees C. Two protocols for surface coating were analyzed for hemostatic parameters and metabolic status, a heparin-based coating (CHC, Corline Heparin Conjugate) without further anticoagulation and a passivating coating (MPC, 2-methacryloyloxethyl phosphorylcholine) with added anticoagulants (enoxaparin, ENOX; or fondaparinux, FPX). Employing the MPC-based coating, the anticoagulants enoxaparin and fondaparinux were compared regarding their differential effects on plasmatic coagulation by thrombelastometry and on platelet activation by flowcytometry and platelet function assays. ResultsUsing the CHC coating, significant coagulation cascade activation was observed, whereas parameters remained mostly unchanged with MPC-based protocols. Extended incubation caused significantly elevated levels of the soluble membrane attack complex. Neither ENOX nor FPX caused a relevant impairment of platelet function or activation capacity and thrombelastometric parameters remained unchanged with both protocols. For translational purposes, we additionally modeled endotoxemia with the MPC-based protocols by incubating with lipopolysaccharide plus/minus thrombin. While coagulation parameters remained unchanged, elevated Interleukin 8 and Matrix Metalloproteinase 9 demonstrated preserved immune cell responsiveness. ConclusionsThe MPC-based protocols demonstrated better hemocompatibility compared to CHC, and ENOX and FPX proved useful for additional anticoagulation. Furthermore, this simple-to-use whole blood model may be useful for experimental analyses of the early coagulatory and immunological response without decalcification.
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43. |
- Forsvall, Andreas, et al.
(author)
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Evaluation of the Forsvall biopsy needle in an ex vivo model of transrectal prostate biopsy - a novel needle design with the objective to reduce the risk of post-biopsy infection
- 2021
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In: Scandinavian Journal of Urology. - : Medical Journals Sweden AB. - 2168-1805 .- 2168-1813. ; 55:3, s. 227-234
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Journal article (peer-reviewed)abstract
- Background Transrectal prostate biopsy (TRbx) transfers colonic bacteria into prostatic tissue, potentially causing infectious complications, including sepsis. Our objective was to determine whether biopsy needle shape, surface properties and sampling mechanism affect the number of bacteria transferred through the colon wall, and evaluate a novel needle with improved properties. Methods The standard Tru-Cut biopsy needle used today was evaluated for mechanisms of bacterial transfer in a pilot study. A novel Tru-Cut needle (Forsvall needle prototype) was developed. TRbx was simulated using human colons ex-vivo. Four subtypes of the prototype needle were compared with a standard Tru-Cut needle (BARD 18 G). Prototype and standard needles were used to puncture 4 different colon specimens in 10 randomized sites per colon. Needles were submerged into culture media to capture translocated bacteria. The media was cultured on blood agar and then the total amount of transferred bacteria was calculated for each needle. The primary outcome measure was the percent reduction of bacteria translocated by the prototype needles relative to the standard needle. Secondary outcome measures were the effects of tip design and coating on the percent reduction of translocated bacteria. Results Prototype needles reduced the number of translocated bacteria by, on average, 96.0% (95% confidence interval 93.0-97.7%; p < 0.001) relative to the standard needle. This percent reduction was not significantly affected by prototype needle tip style or surface coating. Conclusions The Forsvall needle significantly reduces colonic bacterial translocation, suggesting that it could reduce infectious complications in prostate biopsy. A clinical trial has been initiated.
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44. |
- Procter, Philip, et al.
(author)
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Gluing Living Bone Using a Biomimetic Bioadhesive : From Initial Cut to Final Healing
- 2021
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In: Frontiers in Bioengineering and Biotechnology. - : Frontiers Media S.A.. - 2296-4185. ; 9
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Journal article (peer-reviewed)abstract
- Osteoporotic fractures are a growing issue due to the increasing incidence of osteoporosis worldwide. High reoperation rates in osteoporotic fractures call for investigation into new methods in improving fixation of osteoporotic bones. In the present study, the strength of a recently developed bone bioadhesive, OsStictm, was evaluated in vivo using a novel bone core assay in a murine animal model at 0, 3, 7, 14, 28, and 42 days. Histology and micro-CT were obtained at all time points, and the mean peak pull-out force was assessed on days 0–28. The adhesive provided immediate fixation to the bone core. The mean peak bone core pull-out force gradually decreased from 6.09 N (σ 1.77 N) at day 0 to a minimum of 3.09 N (σ 1.08 N) at day 7, recovering to 6.37 N (σ 4.18 N) by day 28. The corresponding fibrin (Tisseel) control mean peak bone core pull-out characteristic was 0.27 N (σ 0.27 N) at day 0, with an abrupt increase from 0.37 N (σ 0.28) at day 3, 6.39 N (σ 5.09 N) at day 7, and continuing to increase to 11.34 N (σ 6.5 N) by day 28. The bone cores failed either through core pull-out or by the cancellous part of the core fracturing. Overall, the adhesive does not interrupt healing with pathological changes or rapid resorption. Initially, the adhesive bonded the bone core to the femur, and over time, the adhesive was replaced by a vascularised bone of equivalent quality and quantity to the original bone. At the 42 day time point, 70% of the adhesive in the cancellous compartment and 50% in the cortical compartment had been replaced. The adhesive outwith the bone shell was metabolized by cells that are only removing the material excess with no ectopic bone formation. It is concluded that the adhesive is not a physical and biochemical barrier as the bone heals through the adhesive and is replaced by a normal bone tissue. This adhesive composition meets many of the clinical unmet needs expressed in the literature, and may, after further preclinical assessments, have potential in the repair of bone and osteochondral fragments.
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45. |
- Walladbegi, Java, et al.
(author)
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Three-dimensional bioprinting using a coaxial needle with viscous inks in bone tissue engineering - An in vitro study
- 2020
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In: Annals of Maxillofacial Surgery. - : Medknow. - 2249-3816 .- 2231-0746. ; 10:2, s. 370-376
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Journal article (peer-reviewed)abstract
- Introduction: Vascularized autologous tissue grafts are considered 'gold standard' for the management of larger bony defects in the craniomaxillofacial area. This modality does however carry limitations, such as the absolute requirement for healthy donor tissues and recipient vessels. In addition, the significant morbidity of large bone graft is deterrent to fibula bone flap use. Therefore, less morbid strategies would be beneficial. The purpose of this study was to develop a printing method to manufacture scaffold structure with viable stem cells. Materials and Methods: In total, three different combinations of ground beta tri-calcium phosphate and CELLINK (bioinks) were printed with a nozzle to identify a suitable bioink for three-dimensional printing. Subsequently, a coaxial needle, with three different nozzle gauge combinations, was evaluated for printing of the bioinks. Scaffold structures (grids) were then printed alone and with additional adipose stem cells before being transferred into an active medium and incubated overnight. Following incubation, grid stability was evaluated by assessing the degree of maintained grid outline, and cell viability was determined using the live/dead cell assay. Results: Among the three evaluated combinations of bioinks, two resulted in good printability for bioprinting. Adequate printing was obtained with two out of the three nozzle gauge combinations tested. However, due to the smaller total opening, one combination revealed a better stability. Intact grids with maintained stability were obtained using Ink B23 and Ink B42, and approximately 80% of the printed stem cells were viable following 24 hours. Discussion: Using a coaxial needle enables printing of a stable scaffold with viable stem cells. Furthermore, cell viability is maintained after the bioprinting process.
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46. |
- van Zyl, Martin, et al.
(author)
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Injectable conductive hydrogel restores conduction through ablated myocardium
- 2020
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In: Journal of Cardiovascular Electrophysiology. - : Wiley. - 1045-3873 .- 1540-8167. ; 31:12, s. 3293-3301
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Journal article (peer-reviewed)abstract
- Introduction Therapies for substrate-related arrhythmias include ablation or drugs targeted at altering conductive properties or disruption of slow zones in heterogeneous myocardium. Conductive compounds such as carbon nanotubes may provide a novel personalizable therapy for arrhythmia treatment by allowing tissue homogenization. Methods A nanocellulose carbon nanotube-conductive hydrogel was developed to have conduction properties similar to normal myocardium. Ex vivo perfused canine hearts were studied. Electroanatomic activation mapping of the epicardial surface was performed at baseline, after radiofrequency ablation, and after uniform needle injections of the conductive hydrogel through the injured tissue. Gross histology was used to assess distribution of conductive hydrogel in the tissue. Results The conductive hydrogel viscosity was optimized to decrease with increasing shear rate to allow expression through a syringe. The direct current conductivity under aqueous conduction was 4.3 x 10(-1) S/cm. In four canine hearts, when compared with the homogeneous baseline conduction, isochronal maps demonstrated sequential myocardial activation with a shift in direction of activation to surround the edges of the ablated region. After injection of the conductive hydrogel, isochrones demonstrated conduction through the ablated tissue with activation restored through the ablated tissue. Gross specimen examination demonstrated retention of the hydrogel within the tissue. Conclusions This proof-of-concept study demonstrates that conductive hydrogel can be injected into acutely disrupted myocardium to restore conduction. Future experiments should focus on evaluating long-term retention and biocompatibility of the hydrogel through in vivo experimentation.
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47. |
- Oskarsdotter, Kristin, 1995, et al.
(author)
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Autologous endothelialisation by the stromal vascular fraction on laminin-bioconjugated nanocellulose-alginate scaffolds
- 2023
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In: Biomedical Materials (Bristol). - 1748-605X .- 1748-6041. ; 18:4
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Journal article (peer-reviewed)abstract
- Establishing a vascular network in biofabricated tissue grafts is essential for ensuring graft survival. Such networks are dependent on the ability of the scaffold material to facilitate endothelial cell adhesion; however, the clinical translation potential of tissue-engineered scaffolds is hindered by the lack of available autologous sources of vascular cells. Here, we present a novel approach to achieving autologous endothelialisation in nanocellulose-based scaffolds by using adipose tissue-derived vascular cells on nanocellulose-based scaffolds. We used sodium periodate-mediated bioconjugation to covalently bind laminin to the scaffold surface and isolated the stromal vascular fraction and endothelial progenitor cells (EPCs; CD31+CD45−) from human lipoaspirate. Additionally, we assessed the adhesive capacity of scaffold bioconjugation in vitro using both adipose tissue-derived cell populations and human umbilical vein endothelial cells. The results showed that the bioconjugated scaffold exhibited remarkably higher cell viability and scaffold surface coverage by adhesion regardless of cell type, whereas control groups comprising cells on non-bioconjugated scaffolds exhibited minimal cell adhesion across all cell types. Furthermore, on culture day 3, EPCs seeded on laminin-bioconjugated scaffolds showed positive immunofluorescence staining for the endothelial markers CD31 and CD34, suggesting that the scaffolds promoted progenitor differentiation into mature endothelial cells. These findings present a possible strategy for generating autologous vasculature and thereby increase the clinical relevance of 3D-bioprinted nanocellulose-based constructs.
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48. |
- Apelgren, Peter, et al.
(author)
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Long-term in vivo integrity and safety of3D-bioprinted cartilaginous constructs
- 2021
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In: Journal of Biomedical Materials Research Part B-Applied Biomaterials. - : Wiley. - 1552-4973 .- 1552-4981. ; 109:1, s. 126-136
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Journal article (peer-reviewed)abstract
- Long-term stability and biological safety are crucial for translation of 3D-bioprinting technology into clinical applications. Here, we addressed the long-term safety and stability issues associated with 3D-bioprinted constructs comprising a cellulose scaffold and human cells (chondrocytes and stem cells) over a period of 10 months in nude mice. Our findings showed that increasing unconfined compression strength over time significantly improved the mechanical stability of the cell-containing constructs relative to cell-free scaffolds. Additionally, the cell-free constructs exhibited a mean compressive stress and stiffness (compressive modulus) of 0.04 +/- 0.05 MPa and 0.14 +/- 0.18 MPa, respectively, whereas these values for the cell-containing constructs were 0.11 +/- 0.08 MPa (p= .019) and 0.53 +/- 0.59 MPa (p= .012), respectively. Moreover, histomorphologic analysis revealed that cartilage formed from the cell-containing constructs harbored an abundance of proliferating chondrocytes in clusters, and after 10 months, resembled native cartilage. Furthermore, extension of the experiment over the complete lifecycle of the animal model revealed no signs of ossification, fibrosis, necrosis, or implant-related tumor development in the 3D-bioprinted constructs. These findings confirm the in vivo biological safety and mechanical stability of 3D-bioprinted cartilaginous tissues and support their potential translation into clinical applications.
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49. |
- Kumosa, Lucas, et al.
(author)
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Profound alterations in brain tissue linked to hypoxic episode after device implantation
- 2021
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In: Biomaterials. - : Elsevier BV. - 0142-9612. ; 278, s. 1-13
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Journal article (peer-reviewed)abstract
- To enable authentic interfacing with neuronal structures in the brain, preventing alterations of tissue during implantation of devices is critical. By transiently implanting oxygen microsensors into rat cortex cerebri for 2 h, substantial and long lasting (>1 h) hypoxia is routinely generated in surrounding tissues; this hypoxia is linked to implantation generated compressive forces. Preferential loss of larger neurons and reduced metabolic components in surviving neurons indicates decreased viability one week after such hypoxic, compressive implantations. By devising an implantation method that relaxes compressive forces; magnitude and duration of hypoxia generated following such an implantation are ameliorated and neurons appear similar to naïve tissues. In line with these observations, astrocyte proliferation was significantly more pronounced for more hypoxic, compressive implantations. Surprisingly, astrocyte processes were frequently found to traverse cellular boundaries into nearby neuronal nuclei, indicating injury induction of a previously not described astrocyte-neuron interaction. Found more frequently in less hypoxic, force-relaxed insertions and thus correlating to a more beneficial outcome, this finding may suggest a novel protective mechanism. In conclusion, substantial and long lasting insertion induced hypoxia around brain implants, a previously overlooked factor, is linked to significant adverse alterations in nervous tissue.
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50. |
- Greco, Gabriele, et al.
(author)
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Tyrosine residues mediate supercontraction in biomimetic spider silk
- 2021
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In: Communications materials. - : Springer Science and Business Media LLC. - 2662-4443. ; 2:1
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Journal article (peer-reviewed)abstract
- Exposing spider silk to wet conditions can cause supercontraction. Here, tyrosine amino acid residues within the amorphous regions are found to contribute to supercontraction, which can be controlled by protein engineering. Water and humidity severely affect the material properties of spider major ampullate silk, causing the fiber to become plasticized, contract, swell and undergo torsion. Several amino acid residue types have been proposed to be involved in this process, but the complex composition of the native fiber complicates detailed investigations. Here, we observe supercontraction in biomimetically produced artificial spider silk fibers composed of defined proteins. We found experimental evidence that proline is not the sole residue responsible for supercontraction and that tyrosine residues in the amorphous regions of the silk fiber play an important role. Furthermore, we show that the response of artificial silk fibers to humidity can be tuned, which is important for the development of materials for applications in wet environments, eg producing water resistant fibers with maximal strain at break and toughness modulus.
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