| 1. |
- Afewerki, Samson, et al.
(författare)
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Combined Catalysis for Engineering Bioinspired, Lignin-Based, Long-Lasting, Adhesive, Self-Mending, Antimicrobial Hydrogels
- 2020
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Ingår i: ACS Nano. - : American Chemical Society (ACS). - 1936-0851 .- 1936-086X. ; 14:12, s. 17004-17017
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Tidskriftsartikel (refereegranskat)abstract
- The engineering of multifunctional biomaterials using a facile sustainable methodology that follows the principles of green chemistry is still largely unexplored but would be very beneficial to the world. Here, the employment of catalytic reactions in combination with biomass-derived starting materials in the design of biomaterials would promote the development of eco-friendly technologies and sustainable materials. Herein, we disclose the combination of two catalytic cycles (combined catalysis) comprising oxidative decarboxylation and quinone-catechol redox catalysis for engineering lignin-based multifunctional antimicrobial hydrogels. The bioinspired design mimics the catechol chemistry employed by marine mussels in nature. The resultant multifunctional sustainable hydrogels (1) are robust and elastic, (2) have strong antimicrobial activity, (3) are adhesive to skin tissue and various other surfaces, and (4) are able to self-mend. A systematic characterization was carried out to fully elucidate and understand the facile and efficient catalytic strategy and the subsequent multifunctional materials. Electron paramagnetic resonance analysis confirmed the long-lasting quinone-catechol redox environment within the hydrogel system. Initial in vitro biocompatibility studies demonstrated the low toxicity of the hydrogels. This proof-of-concept strategy could be developed into an important technological platform for the eco-friendly, bioinspired design of other multifunctional hydrogels and their use in various biomedical and flexible electronic applications.
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| 2. |
- Basu, Alex, et al.
(författare)
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Ion-crosslinked wood-derived nanocellulose hydrogels with tunable antibacterial properties : Candidate materials for advanced wound care applications
- 2018
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Ingår i: Carbohydrate Polymers. - : Elsevier BV. - 0144-8617 .- 1879-1344. ; 181, s. 345-350
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Tidskriftsartikel (refereegranskat)abstract
- Development of advanced dressings with antimicrobial properties for the treatment of infected wounds is an important approach in the fight against evolution of antibiotic resistant bacterial strains. Herein, the effects of ion-crosslinked nanocellulose hydrogels on bacteria commonly found in infected wounds were investigated in vitro. By using divalent calcium or copper ions as crosslinking agents, different antibacterial properties against the bacterial strains Staphylococcus epidermidis and Pseudomonas aeruginosa were obtained. Calcium crosslinked hydrogels were found to retard S. epidermidis growth (up to 266% increase in lag time, 36% increase in doubling time) and inhibited P. aeruginosa biofilm formation, while copper crosslinked hydrogels prevented S. epidermidis growth and were bacteriostatic towards P. aeruginosa (49% increase in lag time, 78% increase in doubling time). The wound dressing candidates furthermore displayed barrier properties towards both S. epidermidis and P. aeruginosa, hence making them interesting for further development of advanced wound dressings with tunable antibacterial properties.
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| 3. |
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| 4. |
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| 5. |
- Hulsart Billström, Gry, 1982-, et al.
(författare)
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Thromboinflammation as bioactivity assessment of H2O2-alkali modified titanium surfaces
- 2019
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Ingår i: Journal of materials science. Materials in medicine. - : Springer Science and Business Media LLC. - 0957-4530 .- 1573-4838. ; 30:6
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Tidskriftsartikel (refereegranskat)abstract
- The release of growth factors from platelets, mediated by the coagulation and the complement system, plays an important role in the bone formation around implants. This study aimed at exploring the thromboinflammatory response of H2O2-alkali soaked commercially pure titanium grade 2 discs exposed to whole human blood, as a way to assess the bioactivity of the discs. Commercially pure titanium grade 2 discs were modified by soaking in H2O2, NaOH and Ca(OH)2. The platelet aggregation, coagulation activation and complement activation was assessed by exposing the discs to fresh whole blood from human donors. The platelet aggregation was examined by a cell counter and the coagulation and complement activation were assessed by ELISA-measurements of the concentration of thrombin-antithrombin complex, C3a and terminal complement complex. The modified surface showed a statistically significant increased platelet aggregation, coagulation activation and complement activation compared to unexposed blood. The surface also showed a statistically significant increase of coagulation activation compared to PVC. The results of this study showed that the H2O2-alkali soaked surfaces induced a thromboinflammatory response that indicates that the surfaces are bioactive.
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| 6. |
- Janson, Oscar, et al.
(författare)
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Debridement of Bacterial Biofilms with TiO2/H2O2 Solutions and Visible Light Irradiation
- 2018
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Ingår i: International Journal of Biomaterials. - : Hindawi Publishing Corporation. - 1687-8787 .- 1687-8795. ; 2018
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Tidskriftsartikel (refereegranskat)abstract
- Objectives. The aim of the study was to explore the debridement efficacy of different solutions of H2O2 and rutile particles against Staphylococcus epidermidis and Pseudomonas aeruginosa biofilms attached to titanium surfaces when exposed to visible light. Materials and Methods. Titanium discs cultivated with biofilms of Staphylococcus epidermidis or Pseudomonas aeruginosa were subjected for 1 min to suspensions consisting of rutile particles mixed with high (950 mM) or low (2 mM) concentrations of H2O2 under visible light irradiation (405 nm; 2.1 mW/cm2). Discs were rinsed and the degree of debridement was determined through scanning electron microscopy and viability assessment of the remaining bacteria using luminescence measurements and/or a metabolic activity assay. Results. Cleaning mixtures containing the higher concentration of H2O2 showed a significantly improved debridement compared to the negative control in all experiments. The addition of rutile particles was shown to have a statistically significant effect in one test with S. epidermidis. Limited evidence of the catalytic effect of visible light irradiation was seen, but effects were relatively small and statistically insignificant. Conclusions. H2O2 at a concentration of 950 mM proved to be the strongest contribution to the debridement and bactericidal effect of the cleaning techniques tested in this study.
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| 7. |
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| 8. |
- Janson, Oscar, et al.
(författare)
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Evaluation of an alkali-treated and hydroxyapatite-coated orthopedic implant loaded with tobramycin
- 2019
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Ingår i: Journal of biomaterials applications. - : SAGE Publications. - 0885-3282 .- 1530-8022. ; 34:5, s. 699-720
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Tidskriftsartikel (refereegranskat)abstract
- An approximately 1-µm thick hydroxyapatite coating was biomimetically deposited on an alkali-treated, commercially available orthopedic screw surface (type II anodized titanium). Tobramycin loaded into the coating via a simple soaking method was shown to provide a sustained release above the minimal inhibitory concentration 0.2 µg/µl for up to two days. Agar diffusion tests showed that the tobramycin-loaded coating was able to produce a zone of inhibition against Staphylococcus aureus for up to five days. Biocompatibility testing using outgrowth endothelial cells and primary osteoblasts suggested that good cell compatibility of the coating can be expected in vivo. A rabbit distal femur condyle model was used for in vivo evaluation of the antibacterial efficacy of the tobramycin-loaded coating, and this pilot study showed that the release of tobramycin was sufficient to locally eliminate very large amounts of bacteria in vivo (inoculation dose 104–105 CFU S. aureus/test site).
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| 9. |
- Janson, Oscar, et al.
(författare)
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Organic degradation potential of a TiO2/H2O2/UV-Vis system for dental applications
- 2017
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Ingår i: Journal of Dentistry. - : Elsevier BV. - 0300-5712 .- 1879-176X. ; 67, s. 53-57
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Tidskriftsartikel (refereegranskat)abstract
- ObjectivesThe combination of TiO2 and H2O2 under light activation constitutes a promising method for disinfection of dental prosthetics and implants, due to production of reactive oxygen species (ROS). The aim of this work was to investigate the organic degradation ability of TiO2 particles in combination with H2O2 and under light activation utilizing the organic dye rhodamine B (RhB).MethodsFive different types of TiO2 particles, consisting of anatase, rutile, or a mixture of these crystalline phases, were combined with H2O2 and RhB, and subsequently exposed to UV (365 nm) or visible (405 nm) light at an irradiance of 2.1 mW/cm2.ResultsIt was found that rutile in combination with low concentrations of H2O2 (1.0–3.5 mM) resulted in a degradation of RhB of 96% and 77% after 10 min exposure to 365 nm and 405 nm light, respectively, which was the highest degradation of all test groups. Control measurements performed without light irradiation or irradiation at 470 nm, or without TiO2 particles resulted in little or no degradation of RhB.ConclusionsLow H2O2 concentrations (1.0 mM–3.5 mM) and visible light (405 nm) used in combination with rutile TiO2 particles showed the highest RhB degradation capacity.Clinical significanceA combination of TiO2 particles and H2O2 exposed to low energy UV or high energy visible light has an organic degradation capability that could be utilized in applications to kill or inactivate bacteria on medical devices such as dental implants for treatment against, e.g., peri-implantitis.
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| 10. |
- Janson, Oscar, et al.
(författare)
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Titanium surface modification to enhance antibacterial and bioactive properties while retaining biocompatibility
- 2019
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Ingår i: Materials science & engineering. C, biomimetic materials, sensors and systems. - : Elsevier BV. - 0928-4931 .- 1873-0191. ; 96, s. 272-279
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Tidskriftsartikel (refereegranskat)abstract
- Bacterial infections associated with metal implants are severe problems affecting a considerable amount of people with dental or orthopedic implants. This study aims to examine the antibacterial effect of a Titanium-peroxy gel layer on the modified surface of commercially pure titanium grade 2. Variations in a multi-step surface modification procedure were tested to determine the best combination that provided an antibacterial effect while enhancing bioactivity without compromising biocompatibility. Soaking the surfaces in 30 wt% hydrogen peroxide held at 80 °C provided antibacterial activity while subsequent surface treatments in concentrated sodium and calcium hydroxide solutions were preformed to enhance bioactivity. Staphylococcus epidermidis was used to determine the antibacterial effect through both direct contact and biofilm inhibition tests while human dermal fibroblast cells and MC3T3 pre osteoblast cells were utilized to test biocompatibility. The greatest antibacterial effect was observed with only hydrogen peroxide treatment, but the resulting surface was neither bioactive nor biocompatible. It was found that subsequent surface treatments with sodium hydroxide followed by calcium hydroxide provided a bioactive surface that was also biocompatible. Additionally, a final treatment with autoclaving showed positive effects with regards to enhanced bioactivity. This multi-step surface modification procedure offers a promising, non-antibiotic, solution for combatting infections associated with biomedical implants.
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| 11. |
- Katsaros, Ioannis, et al.
(författare)
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Bioactive Silicon Nitride Implant Surfaces with Maintained Antibacterial Properties
- 2022
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Ingår i: Journal of Functional Biomaterials. - : MDPI. - 2079-4983. ; 13:3
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Tidskriftsartikel (refereegranskat)abstract
- Silicon nitride (Si3N4) is a promising biomaterial, currently used in spinal fusion implants. Such implants should result in high vertebral union rates without major complications. However, pseudarthrosis remains an important complication that could lead to a need for implant replacement. Making silicon nitride implants more bioactive could lead to higher fusion rates, and reduce the incidence of pseudarthrosis. In this study, it was hypothesized that creating a highly negatively charged Si3N4 surface would enhance its bioactivity without affecting the antibacterial nature of the material. To this end, samples were thermally, chemically, and thermochemically treated. Apatite formation was examined for a 21-day immersion period as an in-vitro estimate of bioactivity. Staphylococcus aureus bacteria were inoculated on the surface of the samples, and their viability was investigated. It was found that the thermochemically and chemically treated samples exhibited enhanced bioactivity, as demonstrated by the increased spontaneous formation of apatite on their surface. All modified samples showed a reduction in the bacterial population; however, no statistically significant differences were noticed between groups. This study successfully demonstrated a simple method to improve the in vitro bioactivity of Si3N4 implants while maintaining the bacteriostatic properties.
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| 12. |
- Katsiotis, Christos S., et al.
(författare)
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3D-Printed Mesoporous Carrier System for Delivery of Poorly Soluble Drugs
- 2021
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Ingår i: Pharmaceutics. - : MDPI. - 1999-4923. ; 13:7
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Tidskriftsartikel (refereegranskat)abstract
- Fused deposition modelling (FDM) is the most extensively employed 3D-printing technique used in pharmaceutical applications, and offers fast and facile formulation development of personalized dosage forms. In the present study, mesoporous materials were incorporated into a thermoplastic filament produced via hot-melt extrusion and used to produce oral dosage forms via FDM. Mesoporous materials are known to be highly effective for the amorphization and stabilization of poorly soluble drugs, and were therefore studied in order to determine their ability to enhance the drug-release properties in 3D-printed tablets. Celecoxib was selected as the model poorly soluble drug, and was loaded into mesoporous silica (MCM-41) or mesoporous magnesium carbonate. In vitro drug release tests showed that the printed tablets produced up to 3.6 and 1.5 times higher drug concentrations, and up to 4.4 and 1.9 times higher release percentages, compared to the crystalline drug or the corresponding plain drug-loaded mesoporous materials, respectively. This novel approach utilizing drug-loaded mesoporous materials in a printed tablet via FDM shows great promise in achieving personalized oral dosage forms for poorly soluble drugs.
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| 13. |
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| 14. |
- Katsiotis, Christos S.
(författare)
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Additive Manufacturing and Mesoporous Materials for Pharmaceutical Applications
- 2024
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Additive Manufacturing (AM), over the past decade, has evolved into a versatile technology with significant applications in pharmaceutical research. This technology enables the production of drug formulations tailored to individual patients, offering customization in both dosage and dissolution profiles. While challenges in mass production persist, 3D printing, particularly through techniques like Fused Deposition Modeling (FDM) and Semi Solid Extrusion (SSE), proves ideal for crafting smaller batches of personalized dosage forms.A prevalent issue in drug development revolves around poor water solubility, impacting bioavailability upon oral administration. To combat this, the integration of mesoporous materials emerges as a promising strategy to enhance the dissolution of poorly water-soluble drugs. Here, the applicability of mesoporous materials is explored, as well as their incorporation with various AM techniques. Overall, the thesis dives into the investigation of combinatorial formulations, incorporating at least one 3D printed component to address specific requirements in drug delivery. By combining FDM with Selective Laser Sintering (SLS), a hybrid two-compartmental formulation is developed. The durable FDM-printed shell regulates buffer medium access to the contained SLS-produced inserts loaded with the drug. Varying printing parameters and insert combinations within the shell showcase the adjustability and flexibility of this hybrid approach.Tablets with different infill percentages, containing drug-loaded mesoporous materials, are developed. Poorly water-soluble drugs are successfully amorphized within mesoporous material pores, formulated into filaments through Hot Melt Extrusion (HME), and printed via FDM. These tablets exhibit improved dissolution compared to the crystalline drug, with the dissolution behavior regulated also by the infill percentage.The study explores the impact of drug-loaded mesoporous materials on HME-produced filament properties, studying their effect on maximum tensile strength and Young’s modulus. The relationship between these properties and filament printability is investigated. Additionally, a protective effect of mesoporous materials on drugs from thermal degradation is revealed.For Semi Solid Extrusion (SSE) manufactured formulations, a paste is developed, comprising mesoporous material loaded with a poorly water-soluble drug and an excipient. This paste demonstrates favorable rheological properties and easy extrudability via a syringe. The formulation proves versatile for printing dosage forms for both oral and rectal administration, with the printed tablet and suppository exhibiting effective drug release.In conclusion, this work presents valuable strategies for developing patient-tailored dosage forms, addressing specific pharmaceutical challenges like poor solubility. The integration of mesoporous materials and various 3D printing techniques showcases a promising direction for personalized medicine in the pharmaceutical field.
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| 15. |
- Katsiotis, Christos S., et al.
(författare)
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Combinatorial 3D printed dosage forms for a two-step and controlled drug release
- 2023
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Ingår i: European Journal of Pharmaceutical Sciences. - : Elsevier. - 0928-0987 .- 1879-0720. ; 187
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Tidskriftsartikel (refereegranskat)abstract
- Fused deposition modeling (FDM) and selective laser sintering (SLS) are two of the most employed additive manufacturing (AM) techniques within the pharmaceutical research field. Despite the numerous advantages of different AM methods, their respective drawbacks have yet to be fully addressed, and therefore combinatorial systems are starting to emerge. In the present study, hybrid systems comprising SLS inserts and a two-compartment FDM shell are developed to achieve controlled release of the model drug theophylline. Via the use of SLS a partial amorphization of the drug is demonstrated, which can be advantageous in the case of poorly soluble drugs, and it is shown that sintering parameters can regulate the dosage and release kinetics of the drug from the inserts. Furthermore, via different combinations of inserts within the FDM-printed shell, various drug release patterns, such as a two-step or prolonged release, can be achieved. The study serves as a proof of concept, highlighting the advantages of combining two AM techniques, both to overcome their respective shortcomings and to develop modular and highly tunable drug delivery devices.
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| 16. |
- Katsiotis, Christos S., et al.
(författare)
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Development of a simple paste for 3D printing of drug formulations containing a mesoporous material loaded with a poorly water-soluble drug
- 2024
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Ingår i: European journal of pharmaceutics and biopharmaceutics. - : Elsevier. - 0939-6411 .- 1873-3441. ; 198
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Tidskriftsartikel (refereegranskat)abstract
- Poorly soluble drugs represent a substantial portion of emerging drug candidates, posing significant challenges for pharmaceutical formulators. One promising method to enhance the drug’s dissolution rate and, consequently, bioavailability involves transforming them into an amorphous state within mesoporous materials. These materials can then be seamlessly integrated into personalized drug formulations using Additive Manufacturing (AM) techniques, most commonly via Fused Deposition Modeling. Another innovative approach within the realm of AM for mesoporous material-based formulations is semi-solid extrusion (SSE). This study showcases the feasibility of a straightforward yet groundbreaking hybrid 3D printing system employing SSE to incorporate drug-loaded mesoporous magnesium carbonate (MMC) into two different drug formulations, each designed for distinct administration routes. MMC was loaded with the poorly water-soluble drug ibuprofen via a solvent evaporation method and mixed with PEG 400 as a binder and lubricant, facilitating subsequent SSE. The formulation is non-aqueous, unlike most pastes which are used for SSE, and thus is beneficial for the incorporation of poorly water-soluble drugs. The 3D printing process yielded tablets for oral administration and suppositories for rectal administration, which were then analyzed for their dissolution behavior in biorelevant media. These investigations revealed enhancements in the dissolution kinetics of the amorphous drug-loaded MMC formulations. Furthermore, an impressive drug loading of 15.3 % w/w of the total formulation was achieved, marking the highest reported loading for SSE formulations incorporating mesoporous materials to stabilize drugs in their amorphous state by a wide margin. This simple formulation containing PEG 400 also showed advantages over other aqueous formulations for SSE in that the formulations did not exhibit weight loss or changes in size or form during the curing process post-printing. These results underscore the substantial potential of this innovative hybrid 3D printing system for the development of drug dosage forms, particularly for improving the release profile of poorly water-soluble drugs.
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| 17. |
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| 18. |
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| 19. |
- Katsiotis, Christos S., et al.
(författare)
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Processability of mesoporous materials in fused deposition modeling for drug delivery of a model thermolabile drug
- 2023
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Ingår i: International Journal of Pharmaceutics. - : Elsevier. - 2590-1567. ; 5
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Tidskriftsartikel (refereegranskat)abstract
- The incorporation of drug-loaded mesoporous materials in dosage forms prepared with fused deposition modeling (FDM) has shown the potential to solve challenges relating to additive manufacturing techniques, such as the stability of poorly-soluble drugs in the amorphous state. However, the addition of these non-melting mesoporous materials significantly affects the mechanical properties of the filament used in FDM, which in turn affects the printability of the feedstock material. Therefore, in this study a full-factorial experimental design was utilized to investigate different processing parameters of the hot melt extrusion process, their effect on various mechanical properties and the potential correlation with the filaments' printability. The thermolabile, poorly-soluble drug ibuprofen was utilized as a model drug to assess the potential of two mesoporous materials, Mesoporous Magnesium Carbonate (MMC) and a silica-based material (MCM-41), to thermally protect the loaded drug. Factorial and principal components analysis displayed a correlation between non-printable MCM-41 filaments and their mechanical properties where printable filaments had a maximum stress >7.5 MPa and a Young's modulus >83 MPa. For MMC samples there was no clear correlation, which was in large part attributed to the filaments' inconsistencies and imperfections. Finally, both mesoporous materials displayed a thermal protective feature, as the decomposition due to the thermal degradation of a significant portion of the thermolabile drug was shifted to higher temperatures post-loading. This highlights the potential capability of such a system to be implemented for thermosensitive drugs in FDM applications.
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| 20. |
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| 21. |
- Pochard, Isabelle, et al.
(författare)
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Amine-functionalised mesoporous magnesium carbonate : Dielectric spectroscopy studies of interactions with water and stability
- 2018
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Ingår i: Materials Chemistry and Physics. - : ELSEVIER SCIENCE SA. - 0254-0584 .- 1879-3312. ; 216, s. 332-338
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Tidskriftsartikel (refereegranskat)abstract
- A mesoporous magnesium carbonate (MMC) material that was first described in 2013 is currently being investigated for several industrial and life-science-based applications. In this paper, the effect of functionalising the surface of MMC with amine groups on the water interaction properties of the material is investigated in detail. Amine functionalisation enhanced the stability and water sorption-release properties of the material. This is explained by the low affinity between amine-functionalised MMC and water molecules, as attested by the high free/total water ratio shown by dielectric spectroscopy. This low affinity had an impact on the total amount of adsorbed water at low relative humidities (RHs) but not at high RHs. The functionalisation of MMC with amine groups also stabilised the material in moist environments, hindering spontaneous crystallisation. These results provide a more fundamental understanding of the water interaction properties of MMC and are also expected to facilitate optimisation of the stability of materials like this for novel drug formulations and other life-science applications, as well as for their use in humidity control.
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| 22. |
- Pochard, Isabelle, et al.
(författare)
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Dielectric Spectroscopy Study of Water Behavior in Calcined Upsalite : A Mesoporous Magnesium Carbonate without Organic Surface Groups
- 2015
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Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 119:27, s. 15680-15688
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Tidskriftsartikel (refereegranskat)abstract
- The water sorption properties and the dielectric spectroscopy response of calcined Upsalite?, a novel mesoporous and amorphous magnesium carbonate material candidate for several life-science based application areas, were investigated. The calcination of Upsalite? at 250°C, which removes organic groups present in the uncalcined material, is found to significantly affect the behaviour of adsorbed water. The proportion of free to bound water is considerably higher in the calcined material as compared to the uncalcined counterpart for relative humidities above ? 80 %. The amount of free water in calcined Upsalite? remains high even when the relative humidity is subsequently decreased and is the most likely cause of crystallization of the material into nesquehonite upon high humidity storage. In chorus, the presence of organic groups in uncalcined Upalite? most likely accounts for the higher binding degree of adsorbed water and, thus, the less likelihood of water-induced crystallization of this version of the material. Two dielectric relaxation processes were observed in calcined Upsalite? and were attributed to a Maxwell-Wagner and a Stern-layer relaxation process, respectively. The presented results create a fundamental understanding of water interaction properties in the novel mesoporous magnesium carbonate material Upsalite? and are expected to facilitate optimization of the stability of the material while simultaneously ensuring the lack of toxic surface groups; properties of importance for novel drug formulations and other life-science applications.
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| 23. |
- Soininen, Antti J., et al.
(författare)
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Dynamics of water confined in mesoporous magnesium carbonate
- 2016
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 145:23
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Tidskriftsartikel (refereegranskat)abstract
- We have measured the dynamics of water confined in a porous magnesium carbonate material, Upsalite (R), using the high-resolution neutron backscattering spectrometer SPHERES. We found quasielastic scattering that does not flatten out up to 360 K, which means that the dynamics of water are much slower than in other matrix materials. Specifically, a single Lorentzian line could be fitted to the quasielastic part of the acquired spectra between 220 and 360 K. This, accompanied by an elastic line from dynamically frozen water present at all experimental temperatures, even above the melting point, signaled a significant amount of bound or slow water.
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| 24. |
- Sörensen, Jan Henrik, et al.
(författare)
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Biomimetic Hydroxyapatite Coated Titanium Screws Demonstrate Rapid Implant Stabilization and Safe Removal In-Vivo
- 2015
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Ingår i: Journal of Biomaterials and Nanobiotechnology. - : Scientific Research Publishing, Inc.. - 2158-7027 .- 2158-7043. ; 6, s. 20-35
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Tidskriftsartikel (refereegranskat)abstract
- The early fixation of bone screws after surgical implantation still remains a challenge in the fieldof traumatology. Whilst hydroxyapatite (HA) coatings are known to enhance the fixation of implants;their removal at a later time-point may be problematic. An HA coating has been developedto demonstrate that both implant fixation and safe removal are feasible in the same design. Accordinglythe aim of this study was to compare the in-vivo performance of thin biomimetic HA coatedtitanium screws to uncoated counterparts used as control after bilateral implantation in the femoralcondyle of 36 New Zealand White Rabbits. The screws were analysed macroscopically, byhistology, micro-CT and biomechanically at both two and six weeks post-implantation. The HAcoated screws demonstrated excellent biocompatibility. At two weeks the HA coated screws demonstrateda significant increase in removal torque values as well as a strong trend towards higherpull-out forces. In addition histology confirmed a higher degree of osseointegration and directbone to implant contact. At six weeks no difference in pull-out force and removal torque could bedetected. SEM images confirmed the absence of any residual HA coating indicating a fast coatingdegradation in-vivo. The low level of removal torque after full osseointegration at 6 weeks supportsthe feasibility of safe and easy removal of the implant. The HA coating under study appearsto offer a unique characteristic of enhanced fixation with a minimal increase in removal torqueafter full osseointegration. This may be of value in clinical applications where it is necessary toassure both screw fixation and later removal.
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| 25. |
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| 26. |
- Welch, Ken, 1968-
(författare)
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Electrodynamic and Mechanical Spectroscopy Method Development and Analysis Relating to Materials with Biotechnological Applications
- 2006
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Materials with biotechnological applications and materials that interact with the biological environment play an ever increasing role in our lives and society. In order to be able to tailor specific properties of these materials to suit their intended applications, it is important to gain a deeper understanding of the relationship between the material structure and its function. This thesis contributes to the goal of achieving a better understanding of the functional properties of materials through the development of novel characterizing methods as well as the analysis of such materials. Electrodynamic and mechanical spectroscopy methods are developed or employed in the characterization of three classes of materials, namely, pharmaceutical, biomedical and biological materials. Two electrodynamic methods utilizing conductivity measurements were developed for the investigation of drug release from pharmaceutical dosage forms, particularly in low liquid volumes. Furthermore, a mechanical spectroscopy method based on the split Hopkinson pressure bar setup was developed for the viscoelastic characterization of pharmaceutical compacts. It was shown that this method is a valuable complement to other methods of characterization. Dielectric spectroscopy was integrated with microfabrication techniques to create a method for bacteria detection in a biotechnological application. As well, dielectric spectroscopy was used in the characterization of a novel biomimetic ionomer and was demonstrated to be a powerful tool for studying the bulk molecular dynamics of this functional material. The work presented in this thesis not only provides an enhanced understanding of materials and their functional properties, but also presents new methods that should be useful for the future characterization of such materials.
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| 27. |
- Welch, Ken, 1968-, et al.
(författare)
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Enabling measurements of low-conductance single molecules using gold nanoelectrodes
- 2011
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Ingår i: Nanotechnology. - : Institute of Physics (IOP). - 0957-4484 .- 1361-6528. ; 22:12, s. 125707-
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Tidskriftsartikel (refereegranskat)abstract
- A high resistance nanogap platform was used to trap and electrically characterize 30 nm thiolated double-stranded DNA molecules. High resolution scanning electron microscopy was also used to image the trapped DNA strands. It was found that the surface state of the electrodes and underlying substrate could influence the measurements of trapped molecules when the measured resistances were on the order of TΩ or greater. Hydrophilic surfaces gave rise to larger leakage currents that could potentially mask the underlying signals from molecules positioned in the nanogap. Finally, the careful handling of the samples and control of the environment is essential to avoid surface charging of the oxide substrate layer as these parasitic charges affect electrical measurements of the nanogap. The presented results thus outline some important considerations when making low-conductance measurements on molecules and should prove useful for the characterization of molecules in molecular electronics or sensors employing nanogap platforms.
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| 28. |
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| 29. |
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| 30. |
- Yang, Jiaojiao
(författare)
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Amorphous magnesium carbonate nanomaterials : Synthesis, characterization and applications
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- High surface-to-volume ratio materials, including nanoparticles and mesoporous materials, have a number of applications due to their large surface area and special structures. Traditional approaches for synthesizing high surface-to-volume ratio nanomaterials are often complicated, expensive or environmentally unfriendly. Considering aspects such as availability and safety in terms of environmental or biological contact, magnesium carbonate-based nanomaterials are an interesting and potentially valuable candidate for novel applications. The overall aim of this thesis was to develop novel high surface-to-volume ratio amorphous magnesium carbonate nanomaterials and investigating their possible applications.Amorphous magnesium carbonate nanoparticles (AMN) were successfully synthesized via a simple and low-temperature pathway. The structure and resulting properties of the material can be tailored by changing the final steps in the synthesis process.The ability of AMN to stabilize ibuprofen (IBU) in the amorphous state was investigated. Nanocomposites with IBU:AMN mass ratios as high as to 5:1 were shown to enhance the release rate of IBU in vitro by as much as 83 times compared to IBU in crystalline form. A related nanostructured material, mesoporous magnesium carbonate (MMC), was evaluated as a drug carrier for stabilizing amorphous drugs through the incorporation of the drug within its pores. In this study, MMC was used to release and sustain two poorly soluble drugs (tolfenamic acid and rimonabant) in the supersaturated state with the assistance of hydroxypropyl methylcellulose.AMN was also used to synthesize a novel adhesive together with IBU without the addition of a polymer. This adhesive was transparent, self-healing, shapeable, stretchable and reusable. In addition, the adhesive was able to glue a variety of materials, including metals, glass, paper and plastics (even Teflon).Finally, AMN was used to prepare flexible, transparent and UV-shielding films when incorporated into a PMMA matrix. These films exhibited both UV-shielding properties and moisture absorbance and retention abilities. In addition, the UV- and thermo-stability of these films were enhanced by the addition of AMN.The work presented in this thesis show that the nanomaterials AMN and MMC possess great potential for an extremely broad range of applications, from pharmaceutical applications dealing with poorly soluble drugs to structural applications such as adhesives to applications in optics or electronics such as UV-shielding or moisture barrier films.
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| 31. |
- Yang, Jiaojiao, et al.
(författare)
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Amorphous Magnesium Carbonate Nanoparticles with Strong Stabilizing Capability for Amorphous Ibuprofen
- 2018
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Ingår i: International Journal of Pharmaceutics. - : Elsevier. - 0378-5173 .- 1873-3476. ; 548:1, s. 515-521
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Tidskriftsartikel (refereegranskat)abstract
- Formulating active pharmaceutical ingredients (APIs) in the amorphous state can increase their apparent aqueous solubility and dissolution rate and consequently improve their bioavailability. This study demonstrates, for the first time, the ability to stabilize an API in the amorphous state using a solid dispersion of magnesium carbonate nanoparticles within the API. Specifically, high proportions of ibuprofen were able to be stabilized in the amorphous state using as little as 17% wt/wt amorphous magnesium carbonate nanoparticles, and drug release rates 83 times faster than from the crystalline state were achieved. Biocompatibility of the nanoparticles was demonstrated in vitro using human dermal fibroblasts and stability of the nanocomposite formulation was verified with a storage time of six months. The success of this novel formulation provides a promising approach for achieving improved apparent solubility and enhanced bioavailability of drugs.
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| 32. |
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| 33. |
- Yang, Jiaojiao, et al.
(författare)
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Electrochemically Active, Compressible, and Conducting Silk Fibroin Hydrogels
- 2020
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Ingår i: Industrial & Engineering Chemistry Research. - : AMER CHEMICAL SOC. - 0888-5885 .- 1520-5045. ; 59:19, s. 9310-9317
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Tidskriftsartikel (refereegranskat)abstract
- Silk fibroin-based conducting hydrogels possess hierarchical structural motifs featuring unique properties, but the development of such materials has proven to be challenging. Herein, we develop a novel strategy for the fabrication of a conducting silk fibroin hydrogel based on an interpenetrated network of poly(3,4-ethylene dioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) and silk fibroin. The hydrogel possesses good electrical conductivity and considerable capacitance and cycling stability due to the existence of the PEDOT conducting network, as well as enhanced mechanical properties such as compressibility due to beta-sheets in the silk fibroin network and Ca2+ cross-linking of the PSS components. A symmetric charge storage device based on conductive silk fibroin hydrogel electrodes exhibited a remarkable areal capacitance of 1.1 F cm(-2) at 0.5 mA cm(-2), as well as a good capacitive response under a compressed state. This combination of compression strength and electrochemical properties makes this conducting silk hydrogel a potential material for unconventional energy storage applications.
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| 34. |
- Yang, Jiaojiao, et al.
(författare)
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Enhanced release of poorly water-soluble drugs from synergy between mesoporous magnesium carbonate and polymers
- 2017
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Ingår i: International Journal of Pharmaceutics. - : Elsevier BV. - 0378-5173 .- 1873-3476. ; 525:1, s. 183-190
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Tidskriftsartikel (refereegranskat)abstract
- The need to combat poor water solubility has increased interest in supersaturating drug delivery systems. In this study, amorphous mesoporous magnesium carbonate (MMC) was used as a drug carrier to achieve supersaturation of tolfenamic acid and rimonabant, two drug compounds with low aqueous solubility. The potential synergy between MMC and hydroxypropyl methylcellulose (HPMC), a polymer commonly included as a precipitation inhibitor in drug delivery systems, was explored with the aim of extending the time that high supersaturation levels were maintained. Release was studied under physiological conditions using USP-2 dissolution baths. A new small-scale method was developed to enable measurement of the initial drug release occurring when the MMC is immersed in the water phase. It was shown that MMC and HPMC together resulted in significant supersaturation and that the polymer enabled both the achievement of a higher API concentration and extension of the supersaturation period. The new small-scale release method showed that the release was linearly increasing with the dose and that similar release rates were observed for the two model compounds. It was hence concluded that the MMC release was diffusion limited for the compounds explored.
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| 35. |
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| 36. |
- Yang, Jiaojiao, et al.
(författare)
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Enhanced UV protection and water adsorption properties of transparent poly(methyl methacrylate) films through incorporation of amorphous magnesium carbonate nanoparticles
- 2021
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Ingår i: Journal of polymer research. - : Springer Nature. - 1022-9760 .- 1572-8935. ; 28:8, s. 281-
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Tidskriftsartikel (refereegranskat)abstract
- A simple solution casting approach was used to obtain transparent and flexible poly(methyl methacrylate) (PMMA) films incorporated with 1 – 4% by weight amorphous magnesium carbonate nanoparticles. Optical transparency was retained in visible wavelengths, while transmittance in the UV-B region was reduced by 22% at 310 nm and 58% at 256 nm with the addition of 4 wt. % nanoparticles. Furthermore, the incorporation of the nanoparticles was shown to provide protection for the films under UV-C irradiation (254 nm wavelength, 5 mW cm−2), with the amount of UV degradation decreasing with increasing concentration of nanoparticles. Films with incorporated nanoparticles were also shown to be able to retain adsorbed moisture much better than neat PMMA films; whereas neat PMMA films did not retain moisture, approximately 50% of the adsorbed moisture was retained in films containing 4 wt. % nanoparticles. These enhanced properties of PMMA are of great interest in applications such as flexible and transparent screens for personal electronic devices that require protection from both UV light and moisture.
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| 37. |
- Yang, Jiaojiao, et al.
(författare)
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Multifunctional Polymer-Free Mineral Plastic Adhesives Formed by Multiple Noncovalent Bonds
- 2020
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Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 12:6, s. 7403-7410
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Tidskriftsartikel (refereegranskat)abstract
- Supramolecular adhesives have attracted a great deal of attention in recent years, resulting in their development for different applications. However, creating supramolecular adhesives with reversible and reusable properties is still a challenge. Here, a synthesis route to obtain supramolecular adhesives is presented in which no polymeric compounds are involved in the preparation. The adhesive is formed by intermolecular coulomb forces between amorphous magnesium carbonate nanoparticles and the low-molecular-weight drug ibuprofen, which results in an amorphous composite material that is transparent, shapeable, stretchable, and self-healing, making it reusable. It is demonstrated that this hybrid material provides a simple means of gluing a wide variety of materials, including metals, glass, paper, and plastics, and that is reversible and possesses reusability. The material disrupts the traditional concept of polymer-based adhesives and may be used as a sustainable mineral plastic in applications such as 3D printing.
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| 38. |
- Yang, Jiaojiao, et al.
(författare)
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Synthesis and Characterization of Amorphous Magnesium Carbonate Nanoparticles
- 2019
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Ingår i: Materials Chemistry and Physics. - : Elsevier. - 0254-0584 .- 1879-3312. ; 224, s. 301-307
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Tidskriftsartikel (refereegranskat)abstract
- We report the template-free, low-temperature, environment-friendly synthesis of amorphous magnesium carbonate nanoparticles (AMN). Scanning electron microscopy and transmission electron microscopy show that AMN consist of small nanoparticles approximately 20-65 nm in diameter. Drying temperature and centrifugation are shown to affect the nanostructure and functional properties of the material. Aggregated AMN can be produced with a total pore volume up to 1.72 cm(3)/g and can absorb as much as 24 mmol/g water, substantially surpassing the pore volume and moisture-absorbing capacity of all previously described alkali earth metal carbonates. The nanoparticles are foreseen to be useful in applications such as water sorption, drug delivery and catalysis.
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| 39. |
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| 40. |
- Zaborowska, Magdalena, 1984, et al.
(författare)
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Bacteria-material surface interactions : methodological development for the assessment of implant surface induced antibacterial effects.
- 2015
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Ingår i: Journal of Biomedical Materials Research. Part B - Applied biomaterials. - : Wiley. - 1552-4973 .- 1552-4981. ; 103:1, s. 179-187
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Tidskriftsartikel (refereegranskat)abstract
- The choice of material for implanted prostheses is of great importance concerning bacterial colonization and biofilm formation. Consequently, methods to investigate bacterial behavior are needed in order to develop new infection resistant surfaces. In this study, different methodological setups were used to evaluate the antimicrobial effect of photocatalytic titanium oxide and silver surfaces. Biofilm formation and eradication under static and dynamic culture conditions were studied with the use of the following analytical techniques: viable colony-forming unit (CFU) counting, imprinting, fluorescence, and bioluminescence. The present study demonstrates that different methods are needed in order to evaluate the prophylactic and treatment effects on planktonic and biofilm bacteria and to assess the antimicrobial effect of different surface treatments/coatings. Choosing the right antibacterial testing model for the specific application is also of great importance. Both in situ approaches and indirect methods provide valuable complementary information. © 2014 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2014.
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| 41. |
- Zhang, Peng, et al.
(författare)
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Supersaturation of poorly soluble drugs induced by mesoporous magnesium carbonate
- 2016
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Ingår i: European Journal of Pharmaceutical Sciences. - : Elsevier BV. - 0928-0987 .- 1879-0720. ; 93, s. 468-474
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Tidskriftsartikel (refereegranskat)abstract
- Abstract This work investigates whether the solubility of poorly soluble compounds can be improved by using mesoporous magnesium carbonate (MMC) as the drug delivery system. A solvent evaporation method was used to load structurally diverse model drugs (celecoxib, cinnarizine and griseofulvin) into the pores of MMC. The drug-loaded carrier system was then characterized in terms of porosity, crystallinity, and release profiles by a variety of experimental techniques, including X-ray diffraction, nitrogen adsorption analysis, differential scanning calorimetry, infrared spectroscopy, UV absorption spectroscopy, and thermogravimetric analysis. All three drugs were in a non-crystalline state after loading into the pores of MMC. The concentrations of the drugs in solution over time (a measure of the release rates from loaded MMC) were higher than the corresponding concentrations (dissolution rates) of equal amounts of the crystalline drugs. The release rates were five (celecoxib), three (cinnarizine) and two times (griseofulvin) higher than the dissolution rates of their crystalline counterparts. Supersaturation release profiles were also observed; the areas under the concentration-time curves (0–240 min) were 25- (celecoxib), 5- (cinnarizine) and 2-fold (griseofulvin) greater than those of the crystalline drugs. Hence, MMC shows promise as a general drug delivery vehicle for increasing the bioavailability of compounds with dissolution rate- or solubility-limited absorption.
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| 42. |
- Zhang, Xiaoliang, et al.
(författare)
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Enhanced charge carrier extraction by a highly ordered wrinkled MgZnO thin film for colloidal quantum dot solar cells
- 2017
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Ingår i: Journal of Materials Chemistry C. - 2050-7526 .- 2050-7534. ; 5:42, s. 11111-11120
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Tidskriftsartikel (refereegranskat)abstract
- Efficient charge carrier extraction from a colloidal quantum dot (CQD) solid is crucial for highperformance of CQD solar cells (CQDSCs). Herein, highly ordered wrinkled MgZnO (MZO) thin films aredemonstrated to improve the charge carrier extraction of PbS CQDSCs. The highly ordered wrinkledMZO thin films are prepared using a low-temperature combustion method. The photovoltaicperformances of CQDSCs with a combustion-processed MZO (CP-MZO) thin film as an electrontransport material (ETM) are compared to those of CQDSCs with a conventional sol–gel processed MZO(SGP-MZO) thin film as an ETM. We performed photoluminescence quenching measurements of thecolloidal quantum dot (CQD) solid and charge carrier dynamic analysis of full solar cell devices. Theresults show that the highly ordered wrinkled CP-MZO thin film significantly increases the chargecarrier extraction from the CQD solid and therefore diminishes the charge interfacial recombination atthe CQD/ETM junction, leading to a 15.5% increase in power conversion efficiency. The improvedefficiency in the CP-MZO based CQDSC is also attributed to the compact and pin-hole free CP-MZOthin film.
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