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Biomimetic Bone Scaffolds Based on Co-substituted Calcium Phosphates and Chitosan

Biological hydroxyapatite in its structure contains various trace elements, such as CO32-, Mg2+, Na+, K+, Zn2+, Sr2+, Cl-, F-, which have a crucial role in bone growth. Multi-ionic substitution is one of the most widely used approach to mimic the chemical composition of the bone mineral and to improve the biological performance of calcium phosphate (CaP) materials. Chitosan (CS) is a naturally occurring polysaccharide and promising candidate as polymer matrix in composite scaffolds for bone tissue engineering. The CS can enable porous structure which promotes bone tissue ingrowth and interactions between an implant and natural bone tissue. The CaPs have been prepared by using different biogenic precursors (cuttlefish bone, eggshell, seashell) of Ca2+ ions. The highly porous CaP/chitosan scaffolds have been prepared by freeze-gelation technique. The positive influence of Mg2+ and Sr2+ ions, present in eggshell and cuttlefish bone, on cell viability has been observed. Further, the cuttlefish bone was selected to prepare multi-substituted CaPs, with varying ion content (Sr2+, Mg2+, Zn2+, SeO32-). The effect of the doping on phase composition, crystal structure, morphology and element content of synthesized materials was studied. The precipitated powders were triphasic CaP systems composed of HAp, OCP, and amorphous CaP. Phase transformation and ion release were analysed during 7 days of incubation in simulated body fluid at 37 °C.Highly porous CaP/chitosan composite structure substituted with Sr2+, Mg2+, Zn2+, SeO32- ions have been prepared by freeze-gelation technique. The morphology of scaffolds was imaged by scanning electron microscopy (SEM). Osteogenic genes’ expression (alkaline phosphatase, bone sialoprotein, dentin matrix acidic phosphoprotein 1) after differentiation of human mesenchymal stem cells (hMSCs) cells have been analysed after 14 and 21 days of cell culture by RT-qPCR analysis. The influence of substituted ions present is CaP/chitosan scaffolds on the human mesenchymal stem cells (hMSCs) differentiation performed in a U-CUP bioreactor under perfusion conditioning was investigated after 14 and 21 days of cell culture. The histological and immunohistochemical analysis of cultured bony tissues, and the evaluation of osteogenic genes’ expression indicate that the substituted hydroxyapatite within chitosan scaffold could be preferable for bone-construct development.

biomimetic, composite, co-substitution, hydroxyapatite

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