No abstract

The objective of this study was to develop a collagen/hydroxyapatite (HA) nanocomposite scaffold for bone tissue engineering applications. For this purpose, in situ mineralization of HA was accompanied with formation of collagen hydrogel at condition similar to the physiological condition, pH = 7.4, and 37 C. The physicochemical and biological properties of the in situ scaffold were compared with nanocomposite fabricated by mixing HA powder and collagen hydrogel (powder-mixed scaffold). The HA in this method was formed in the same condition as the in situ method. X-ray diffraction and FTIR analysis of in situ scaffold showed the formation of carbonated HA, similar to bone, while the HA powder in powder-mixed scaffold showed non-carbonated structure. Scanning electron microscopy revealed the formation of fibrillated collagen in both composites. HA was observed in both scaffolds, but with different morphology. The in situ formed HA had a plate-like morphology while the preformed HA showed spherical morphology in the powder-mixed scaffold. The invitro cytocompatibility and osteogenesis activity of scaffolds using osteoblast-like cells (MG-63) showed higher cytocompatibility and more osteogenesis capability of the in situ scaffold in comparison with the powder-mixed scaffold. The results suggest the in situ method as a proper approach for fabrication of HA/collagen scaffolds with similar properties like bone.

Background: Healing the full-thickness skin wounds has remained a challenge.One of the most frequently used grafts for skin regeneration is xenogeneic acellular dermal matrices (ADMs), including bovine ADMs. This study investigated the effect of the source animal age, enzymatic versus non-enzymatic decellularization protocols, and gamma irradiation versus ethylene oxide (EO) sterilization on the scaffold. Methods: ADMs were prepared using the dermises of fetal bovine or calf skins.All groups were decellularized through chemical and mechanical methods, unless T-FADM samples, in which an enzymatic step was added to the decellularization protocol. All groups were sterilized with ethylene oxide (EO), except G-FADM which was sterilized using gamma irradiation. The scaffolds were characterized through scanning electron microscopy, differential scanning calorimetry, tensile test, MTT assay, DNA quantification, and real-time PCR. The performance of the ADMs in wound treatment was also evaluated macroscopically and histologically.Results: All ADMs were effectively decellularized. In comparison to FADM (EOsterilized fetal ADM), morphological, and mechanical properties of G-FADM, T-FADM, and CADM (EOsterilized calf ADM) were changed to different extents. In addition, the CADM and G-FADM were thermally more stable than the FADM and T-FADM. Although all ADMs were noncytotoxic, the wounds of the FADM, T-FADM, and G-FADM groups were contracted to almost 30.0% of the original area on day 7, significantly faster than the CADM (17.5% ± 1.7) and control (12.2% ± 1.59) groups. However, by day 21, all ADMs were mostly closed except for the untreated group (60.1 ± 1.8). Conclusion:Altogether, fetal source and EO-sterilized samples performed better than calf source and gamma-sterilized samples unless in some mechanical properties. There was no added value in using enzymatic treatment during the decellularization process. Our results suggest that the age, decellularization, and

The mechanical property of bone tissue scaffolds is one of the most important aspects in bone tissue engineering that has remained problematic. In our previous study, we fabricated a three-dimensional scaffold from nanohydroxyapatite/gelatin (nHA/Gel) and investigated its efficiency in promoting bone regeneration both in vitro and in vivo. In the present study, the effect of adding silicon carbide (SiC) on the mechanical and biological behaviors of the nHA/Gel/SiC and bone regeneration in vivo were determined. nHA and SiC were synthesized and characterized by the X-ray diffraction pattern and transmission electron microscope image. Layer solvent casting, freeze drying, and lamination techniques were applied to prepare these scaffolds. Then, the biocompatibility and cell adhesion behavior of the synthesized nHA/Gel/SiC scaffolds were investigated. For in vivo studies, rats were categorized into three groups: blank defect, blank scaffold, and rat bone marrow mesenchymal stem cells (rBM-MSCs)/scaffold. After 1, 4, and 12 weeks post-injury, the rats were sacrificed and the calvaria were harvested. Sections with a thickness of 5 µm thickness were prepared and stained with hematoxylin-eosin and Masson's Trichrome, and immunohistochemistry was performed. Our results showed that SiC effectively increased the mechanical properties of the nHA/ Gel/SiC scaffold. No significant differences were observed in biocompatibility, cell adhesion, and cytotoxicity of the nHA/Gel/SiC in comparison with the nHA/Gel nanocomposite. Based on histological and immunohistochemical studies, both osteogenesis and collagenization were significantly higher in the rBM-MSCs/scaffold group, quantitatively and qualitatively. The present study strongly suggests the potential of SiC as an alternative strategy to improve the mechanical and biological properties of bone tissue engineering scaffolds, and shows that the preseeded nHA/Gel/SiC scaffold with rBM-MSCs improves osteogenesis in the engineered bone implant.