Investigation on physicochemical properties of graphene oxide/nano-hydroxyapatite composites and its biomedical applications

Abstract

Graphene oxide/nano-hydroxyapatite (GO/nHAP) composites were synthesized by simultaneous titration method. The GO powder was uniformly dispersed ultrasonically in a solution containing Ca(NO3)2. It was co-titrated with (NH4)2HPO4, during which NH3·H2O was used to maintain pH of about 10. Transmission electron microscopy (TEM) showed that HAP had a drusy acicular crystal structure with 100–200 nm length in the composite. The Ca2+ ions were attracted by the negatively charged oxygen functional groups present on GO sheets. They also oriented the growth of hydroxyapatite preferentially along (112) plane, which was also consistent with X-ray diffractometry (XRD) results. According to X-ray photoelectron spectroscopic (XPS) results, the peak intensities of the C–O and C–C groups increased in the GO/nHAP composite. However, the number of –COO– and C–O–C groups was reduced as well as the position of peaks shifted due to electrostatic interactions. These results were also corroborated with Fourier transform infrared spectroscopy (FTIR). MTT assay indicated that GO/nHAP composites had a significant effect on proliferation of 293T cells and good biomimetic mineralization as shown by in vitro bioactivity assays. EDS spectroscopy confirmed that the Ca/P ratio in calcium phosphate deposits was 1.62, which was close to the ratio of 1.64 in natural bone. The biological performance of GO/nHAP composite proved it to be a promising candidate for bone regeneration and implantation.