Development of genipin-crosslinked and fucoidan-adsorbed nano-hydroxyapatite/hydroxypropyl chitosan composite scaffolds for bone tissue engineering.

Hydroxypropyl chitosan (HPCS) has recently attracted increasing attention in biomedical applications because it has enhanced water solubility, excellent biocompatibility, and better antioxidant and antibacterial activities compared with chitosan. However, HPCS doesn't meet the mechanical strength requirement in bone tissue engineering and is not suitable for cell adhesion and growth because of its hydrophilic nature and low crystallinity. In this study, nano-scaled hydroxyapatite (n-HA) and HPCS were synthesized, respectively, and then n-HA/HPCS nanocomposite scaffolds were developed by incorporating n-HA into HPCS matrix accompanied with crosslinking of HPCS by a naturally occurring compound, genipin (GP), which in turn greatly altered the hydrophilicity and mechanical properties. The nanocomposite scaffolds showed an open structure with interconnected pores and a rough morphology with n-HA inserted in the GP-crosslinked HPCS matrix. The porosity, swelling capacity, compressive strength, fluorescence emission and degradation rate can be regulated by varying GP concentrations and n-HA contents. An osteoconductive and osteogenic marine algae polysaccharide, fucoidan, was further adsorbed to the composite scaffolds via electrostatic interactions. Incorporation of n-HA and adsorption of FD into the composite scaffolds increased ALP activity in 7F2 osteoblast cells and promoted their mineralization. The FD-adsorbed n-HA/HPCS composite scaffolds can be a potential biomaterial for BTE applications.