In situ synthesis of hydroxyapatite nanorods on graphene oxide nanosheets and their reinforcement in biopolymer scaffold

Abstract

Introduction: It is urgently needed to develop composite bone scaffold with excellent mechanical properties and bioactivity in bone tissue engineering. Combining graphene oxide (GO) and hydroxyapatite (HAP) for the reinforcement of biopolymer bone scaffold has emerged as a promising strategy. However, the dispersion of GO and HAP remains to be a big challenge.

Objectives: In this present work, the mechanical properties of GO and the bioactivity of and HAP were combined respectively via in situ synthesis for reinforcing biopolymer bone scaffold.

Methods: GO nanosheets were employed to in situ synthesize GO-HAP nanocomposite via hydrothermal reaction, in which their abundant oxygen-containing groups served as anchor sites for the chelation of Ca²⁺ and then Ca²⁺ absorbed HPO₄^2- via electrovalent bonding to form homogeneously dispersed HAP nanorods. Thereby, the GO-HAP nanocomposite was blended with biopolymer poly-L-lactic acid (PLLA) for fabricating biopolymer scaffold by selective laser sintering (SLS).

Results: GO nanosheets were uniformly decorated with HAP nanorods, which were about 60 nm in length and 5 nm in diameter. The compressive strength and modulus of PLLA/12%GO-HAP were significantly increased by 53.71% and 98.80% compared to the pure PLLA scaffold, respectively, explained on the base of pull out, crack bridging, deflection and pinning mechanisms. Meanwhile, the mineralization experiments indicated the PLLA/GO-HAP scaffold displayed good bioactivity by inducing the formation of apatite layer. Besides, cell culturing experiments demonstrated the favorable cytocompatibility of scaffold by promoting cell adhesion and proliferation.

Conclusions: The present findings show the potential of PLLA/GO-HAP composite scaffold via in situ synthesis in bone tissue engineering.

Keywords: Bioactivity; GO; HAP; In situ synthesis; Mechanical properties.