Carboxymethyl chitosan/gelatin/hydroxyapatite biomimetic cryogels for bone regeneration

Gelation at a temperature below the freezing point of a solvent is known as cryogelation, which has attracted attention in regenerative medicine due to its improved mechanical and structural properties. This study focuses on using cryogelation as a versatile method for fabricating biomimetic scaffolds with improved mechanical strength and larger pore sizes with potential for bone tissue engineering applications. Scaffolds comprising carboxymethyl chitosan/gelatin/nano-hydroxyapatite were formed through cryogelation. The effects of three parameters – namely, cross-linker concentration, mineral content and gelatin-to-polymer ratio – on physical, chemical and mechanical properties were investigated. In this work, MG63 cells were used for an in vitro assay. In addition, an in vivo assay was conducted to investigate the biocompatibility of the nanocomposite scaffolds. The results showed that all scaffolds have a porous structure with interconnected pores with a morphology similar to bone structure. Their pore size, porosity and swelling ratio decreased with an increased cross-linker concentration, while nano-hydroxyapatite had the opposite effect. X-ray diffraction results also showed that the inorganic phase retained its crystallinity in the substrate with a slight decrease in crystal size. In addition, the scaffolds showed no toxicity in either in vitro or in vivo studies. The obtained results showed that biomimetic cryogels based on carboxymethyl chitosan/gelatin/hydroxyapatite have potential for bone tissue engineering.