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| 2. |
- Zhou, Huasi, et al.
(författare)
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Structural Si3N4-SiO2 glass ceramics with bioactive and anti-bacterial properties
- 2024
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Ingår i: Journal of the European Ceramic Society. - : Elsevier. - 0955-2219 .- 1873-619X. ; 44:6, s. 4260-4271
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Tidskriftsartikel (refereegranskat)abstract
- Silicon nitride-based bioceramics have been investigated for biomedical applications due to their good thermo-mechanical, tribological and antibacterial properties. However, biological properties, such as bioactivity that promotes the interaction with tissue, are also important. Silicon dioxide has been found to promote bioactivity. With the aim of combining both advantages, a new Si3N4-SiO2 glass ceramic was developed. Three different compositions were synthesized and sintered by spark plasma sintering. The results showed that β-Si3N4 crystalline is well distributed in the SiO2 matrix. 70SiN samples exhibited the highest mechanical properties with a flexural strength of 452 ± 33 MPa and a toughness of 6.4 ± 0.5 MPa∙m1/2. 50SiN samples exhibited the best bacteriostatic effect due to the synergistic effect of surface chemistry and topography. Apatite was observed on the surfaces of all groups. This study shows that the newly developed Si3N4-SiO2 glass ceramics exhibit promising mechanical and biological properties for biomedical applications.
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| 3. |
- Zhou, Yijun, et al.
(författare)
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A convolutional neural network-based method for the generation of super-resolution 3D models from clinical CT images
- 2024
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Ingår i: Computer Methods and Programs in Biomedicine. - : Elsevier. - 0169-2607 .- 1872-7565. ; 245
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Tidskriftsartikel (refereegranskat)abstract
- Background and ObjectiveThe accurate evaluation of bone mechanical properties is essential for predicting fracture risk based on clinical computed tomography (CT) images. However, blurring and noise in clinical CT images can compromise the accuracy of these predictions, leading to incorrect diagnoses. Although previous studies have explored enhancing trabecular bone CT images to super-resolution (SR), none of these studies have examined the possibility of using clinical CT images from different instruments, typically of lower resolution, as a basis for analysis. Additionally, previous studies rely on 2D SR images, which may not be sufficient for accurate mechanical property evaluation, due to the complex nature of the 3D trabecular bone structures. The objective of this study was to address these limitations.MethodsA workflow was developed that utilizes convolutional neural networks to generate super-resolution 3D models across different clinical CT instruments. The morphological and finite-element-derived mechanical properties of these super-resolution models were compared with ground truth models obtained from micro-CT scans.ResultsA significant improvement in analysis accuracy was demonstrated, where the new SR models increased the accuracy by up to 700% compared with the low-resolution data, i.e. clinical CT images. Additionally, we found that the mixture of different CT image datasets may improve the super-resolution model performance.ConclusionsSuper-resolution images, generated by convolutional neural networks, outperformed clinical CT images in the determination of morphological and mechanical properties. The developed workflow could be implemented for fracture risk prediction, potentially leading to improved diagnoses and subsequent clinical decision making.
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| 4. |
- Zhou, Yijun, 1993-, et al.
(författare)
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Hydroxyapatite particle shape affects screw attachment in cancellous bone when augmented with hydroxyapatite-containing hydrogels
- 2024
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Ingår i: Journal of The Mechanical Behavior of Biomedical Materials. - : Elsevier. - 1751-6161 .- 1878-0180. ; 150
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Tidskriftsartikel (refereegranskat)abstract
- Screw-bone construct failures are a true challenge in orthopaedic implant fixation, particularly in poor quality bone. Whilst augmentation with polymeric or ceramic bone cement can improve the primary stability of the screws, the cement may block the flow of blood and nutrients and hamper bone remodelling. In this study, soft, non-setting biomaterials based on Hyalectin gels and hydroxyapatite (HA) particles with different morphological parameters were evaluated as potential augmentation materials, using a lapine ex vivo bone model. The pull-out force, stiffness, and work to fracture were considered in evaluating screw attachment. The pull-out force of constructs reinforced with Hyalectin containing irregularly shaped nano-HA and spherically shaped micro-HA particles were found to be significantly higher than the control group (no augmentation material). The pull-out stiffness increased for the micro-HA particles and the work to fracture increased for the irregular nano-HA particles. However, there were no significant augmentation effect found for the spherical shaped nano-HA particles. In conclusion, injectable Hyalectin gel loaded with hydroxyapatite particles was found to have a potentially positive effect on the primary stability of screws in trabecular bone, depending on the HA particle shape and size.
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| 5. |
- Du, Xiaoyu, et al.
(författare)
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The porous cantilever beam as a model for spinal implants : Experimental, analytical and finite element analysis of dynamic properties
- 2023
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Ingår i: Mathematical Biosciences and Engineering. - : American Institute of Mathematical Sciences. - 1547-1063 .- 1551-0018. ; 20:4, s. 6273-6293
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Tidskriftsartikel (refereegranskat)abstract
- Investigation of the dynamic properties of implants is essential to ensure safety and compatibility with the host's natural spinal tissue. This paper presents a simplified model of a cantilever beam to investigate the effects of holes/pores on the structures. Free vibration test is one of the most effective methods to measure the dynamic response of a cantilever beam, such as natural frequency and damping ratio. In this study, the natural frequencies of cantilever beams made of polycarbonate (PC) containing various circular open holes were investigated numerically, analytically, and experimentally. The experimental data confirmed the accuracy of the natural frequencies of the cantilever beam with open holes calculated by finite element and analytical models. In addition, two finite element simulation methods, the dynamic explicit and modal dynamic methods, were applied to determine the damping ratios of cantilever beams with open holes. Finite element analysis accurately simulated the damped vibration behavior of cantilever beams with open holes when known material damping properties were applied. The damping behavior of cantilever beams with random pores was simulated, highlighting a completely different relationship between porosity, natural frequency and damping response. The latter highlights the potential of finite element methods to analyze the dynamic response of arbitrary and complex structures, towards improved implant design.
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| 6. |
- Echeverri Correa, Estefania, et al.
(författare)
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Fe and C additions decrease the dissolution rate of silicon nitride coatings and are compatible with microglial viability in 3D collagen hydrogels
- 2023
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Ingår i: Biomaterials Science. - : Royal Society of Medicine Press. - 2047-4830 .- 2047-4849. ; 11:9, s. 3144-3158
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Tidskriftsartikel (refereegranskat)abstract
- Silicon nitride (SiN) coatings may reduce unwanted release of metal ions from metallic implants. However, as SiN slowly dissolves in aqueous solutions, additives that reduce this dissolution rate would likely increase the lifetime and functionality of implants. Adding iron (Fe) and carbon (C) permits tuning of the SiN coatings’ mechanical properties, but their effect on SiN dissolution rates, and their capacity to reduce metal ion release from metallic implant substrates, have yet to be investigated. Such coatings have recently been proposed for use in spinal implants; therefore, it is relevant to assess their impact on the viability of cells expected at the implant site, such as microglia, the resident macrophages of the central nervous system (CNS). To study the effects of Fe and C on the dissolution rate of SiN coatings, compositional gradients of Si, Fe and C in combination with N were generated by physical vapor deposition onto CoCrMo discs. Differences in composition did not affect the surface roughness or the release of Si, Fe or Co ions (the latter from the CoCrMo substrate). Adding Fe and C reduced ion release compared to a SiN reference coating, which was attributed to altered reactivity due to an increase in the fraction of stabilizing Si–C or Fe–C bonds. Extracts from the SiN coatings containing Fe and C were compatible with microglial viability in 2D cultures and 3D collagen hydrogels, to a similar degree as CoCrMo and SiN coated CoCrMo reference extracts. As Fe and C reduced the dissolution rate of SiN-coatings and did not compromise microglial viability, the capacity of these additives to extend the lifetime and functionality of SiN-coated metallic implants warrants further investigation.
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| 7. |
- Echeverri Correa, Estefania, et al.
(författare)
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In vitro 3D model for monitoring glial cell responses to particles and ions released from spinal implants
- 2023
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Konferensbidrag (refereegranskat)abstract
- Spinal implants have been used for decades to treat different spinal conditions. However, certain implant-related complications have been attributed to the release of particles and ions due to corrosion and wear triggering local immune responses including the release of pro-inflammatory cytokines, leading to local inflammation. The impact of these particles and ions on cells from the central nervous system (CNS) remains largely unknown, with few studies examining the effects on glial cells1. Indeed, the particles may migrate to adjacent nervous tissues and increasing our knowledge of the glial cell response is essential since they play a crucial role in maintaining tissue homeostasis and protecting the CNS. Most prior studies have used traditional 2D culture models; however, these lack the 3D spatial arrangement of cells found in tissues where they form important interactions with the extracellular matrix. The aim of this study was to employ an open source bioprinter2 to extrude hydrogels containing glial cells into which experimental implant debris can be introduced, enabling monitoring of cell viability and inflammatory responses by fluorescence microscopy. We have previously established that mono-cultures of microglia and astrocytes can be 3D cultured in collagen hydrogels, and their viability monitored using the caspase-3/7 apoptosis reporter and propidium iodide labelling for cell death. Applying a bioprinting strategy to produce these glial-laden constructs increases the reproducibility of these models, and allows the study of a wide range of types and concentrations of particles, resulting in a valuable tool to increase the knowledge about the biological response generated by particles from spinal implants.
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| 8. |
- Echeverri Correa, Estefania, et al.
(författare)
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Reducing the dissolution rate of silicon nitride coatings for spinal implants using Fe and C as alloying elements
- 2023
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Konferensbidrag (refereegranskat)abstract
- INTRODUCTION: Wear and corrosion may lead to a release of particles and ions from spinal implants, which is a concern because of their potentially detrimental effect on the life span of the implant [1]. Silicon nitride-based coatings have been suggested as an option to reduce the release of metal ions from an implant. In addition, any particles produced will slowly dissolve, releasing only biocompatible ions [2]. It is of high interest to reduce the dissolution rate of the coating to ensure an adequate lifetime [3]. The present study aimed to assess the effect of Fe and C additions to silicon nitride coatings in terms of dissolution rate as well as the impact of the released ions on the in vitro neural cell response.METHODS: Using a combinatorial approach, SiFeCN coatings were deposited on CoCr disc substrates by reactive sputtering in an in-house built equipment. The coatings were characterized in 9 points using x-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). The dissolution behaviour was evaluated by exposing the coated samples to cell media for 14 days. The obtained extracts were used to measure ion release with inductively coupled plasma - optical emission spectrometry (ICP-OES) and to assess cell viability of microglia (C8-B4 cell line) using the MTT assay. RESULTS: The XPS results showed compositional gradients of Si ranging from 35.0 to 47.3 at.%, Fe from 1.4 to 9.3 at.% and C from 4.5 to 13.9 at.%. SEM of focused ion beam (FIB) cross-sections revealed coating thicknesses between 427-534 nm. SEM of the coating after exposure showed substantial signs of dissolution with visibly increased porosity for the SiN coating, while the SiFeCN coatings appeared less affected. SiFeCN coatings appeared more affected by dissolution for increasing Si contents. The estimated dissolution rate of the SiN coating was 8.3 nm/day, while the rate of SiFeCN coatings was 5.2-6.8 nm/day. The ICP results showed a reduction in Co ions from the substrate in the coated samples compared to uncoated CoCr. Moreover, the levels of detected Si ions were lower for the SiFeCN compared to SiN reference. Indirect biocompatibility tests suggested that microglia cell viability was comparable for the SiFeCN coatings, the uncoated CoCr and the SiN coating.DISCUSSION & CONCLUSIONS: The compositional gradients influenced the thickness of the coating, giving a slight thickness increase in the coatings with the increment of Si content. In addition, the ICP results showed the capability of the coating to act as a barrier to the release of ions from the substrate. Furthermore, the presence of Fe and C in the coating causes a decrease in the ion release from the coating, indicative of a lower dissolution rate, which was supported by the thickness measurements. The findings from this study indicate that using Fe and C as alloying elements can lower the dissolution rate of the silicon nitride-based coating while showing positive indications of biocompatibility on neural cells. Therefore, SiFeCN coatings merit further investigation as a future option for spinal implants.REFERENCES: 1Y. Shimamura et al (2008) Spine. 33:351–355. 2M. Pettersson et al (2016) ACS Biomater. Sci. Eng. 2:998–1004. 3C. Skjöldebrand et al (2022) Biomater Sci, 10:3757–3769.ACKNOWLEDGEMENTS: This project has received funding from the European Union’s Horizon 2020 research and innovation program under the Marie Skłodowska-Curie grant agreement No 812765 and from the European Union’s Seventh Framework Programme (FP7/2007-2013), grant agreement GA-310477(LifeLongJoints).
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| 9. |
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| 10. |
- Geissel, Felix J., et al.
(författare)
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Nanostructured Ag-Bioglass Implant Coatings with Antibacterial and Osteogenic Activity
- 2023
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Ingår i: Advanced Materials Interfaces. - : Wiley-VCH Verlagsgesellschaft. - 2196-7350. ; 10:3
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Tidskriftsartikel (refereegranskat)abstract
- Bone implant failure due to aseptic loosening and biofilm infections is an increasing healthcare problem. Implants may be coated with nanoparticles to avoid bacterial colonization and promote osseointegration. However, these nanocoatings often require long, expensive, and complex manufacturing routes with limited clinical translation potential. Here, a multifunctional nanoparticle coating consisting of silver (Ag) and bioglass (BG) is investigated to overcome current limitations by providing synchronously antibacterial and osteogenic effect. Flame spray pyrolysis (FSP) is exploited as a scalable and reproducible process to synthesize large quantities of nanoparticles and deposit them on titanium (Ti) substrates. The deposited nanocoatings show a homogeneous morphology and biomineralize after soaking in simulated body fluid (SBF), while their adhesion on Ti substrates is promoted by in situ flame annealing. The Ag+ ion release from Ag containing BG samples inhibits Staphylococcus aureus biofilm formation up to 3 log units, while the osteogenic responses of pre-osteoblastic cells directly grown on AgBG samples show similar levels of alkaline phosphatase activity, calcium and collagen production when compared to pure Ti. The inexpensively synthesized multifunctional AgBG nanostructured implant coatings exert a high bioactivity and antibacterial response while maintaining high biocompatibility. The insights of this study can direct the development of multifunctional implant coatings.
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