constructing hydroxyapatite/collagen nanocomposite scaffold via in-situ mineralization and comparing in-situ scaffolds and mix-powder in bone defect regeneration in rabbit animal model

Aim and background: in situ mineralization is a simple and effective technique that allows for the fabrication of homogeneous composites with unique morphology and well-distributed ha in hydrogels. in situ synthesis of ha particles in the presence of collagen fibers is a biomimetic approach that can lead to formation of collagen/ha composites similar to bone. this study aimed to compare powder-mixed ha/co hydrogel and in situ synthesized ha/co hydrogel on the regeneration of bone defect in the rabbit animal model. methods: an in-situ collagen/ha scaffold was synthesized by adding ha salts to a collagen acidic solution to mineralize ha in hydrogel at physiological conditions (ph = 7.4 and 37 °c). under the same conditions, a mix-powder collagen/ha scaffold was prepared, but instead of ha salts, ha powder was added. following that, physicochemical properties were investigated. then, in-vitro tests were performed, including cytocompatibility assays, alkaline phosphatase activity assays, and alizarin red staining. afterwards, in-vivo analysis was performed on a critical-sized bone defect in a rabbit animal model, followed by radiological evaluation and microscopical examination. results and discussion: the plate-like ha particles are distributed homogeneously in the in situ ha/co scaffold compared to powder-mixed ha/co scaffold and had a similar structure to bone with carbonated plate-like ha particles and nanofibrilated co matrix. these properties along with excellent cytocompatibility and osteogenicity of in situ ha/collagen nanocomposite candidate it as a proper scaffold for bone tissue engineering. conclusion: in situ ha/co nanocomposite can accelerate bone regeneration due to osteoblastic production of osteocalcin protein, making it a new approach for bone tissue engineering