Fostering biomineralization and biodegradation: nano-hydroxyapatite reinforced iron composites for biodegradable implant application

Abstract

Iron (Fe) is regarded as a candidate material for biodegradable metallic implants due to its biocompatibility and ability to degrade in physiological environemnt. However, the degradation rate in the physiological environment is too slow for clinical applications. It is necessary to accelerate the rate such that the degradation is compatible with tissue growth. Furthermore, the implant material needs to be bioactive for promoting osteointegration, osteoconductivity, cell proliferation and biological apatite formation. Nano-sized bioactive hydroxyapatite (nHA) was incorporated into a porous Fe matrix to enhance the bioactivity and degradation rate. Electrochemical studies in biomemtic NaCl solution, revealed that incorporation of nHA in porous Fe can increase the degradation by 2.5 times compared to the pure iron counterparts with similar porosity. Furthermore, immersion tests in simulated body fluid (SBF) revealed that nHA added samples displayed enhanced biomineralization and degraded at a rate three times faster than pure iron in this environment. The incorporation of nHA into the iron matrix aided in the formation of biomineralized hydroxyapatite. The composite surface promoted the cell adhesion and proliferation and the L929 fibroblast cells exhibited good cell viability. It is proposed that porous morphology incorporated with nHA can improve biomineralization and tailor the degradation rate of Fe-based materials in physiological environment.