Physico-chemical properties and biocompatibility of in situ-hardening polylactide/nano hydroxyapatite composite for bone substitute

Polylactide (PLA) and hydroxyapatite (HA) composite is a promising material for biomedical applications. The bioresorbability and adequate strength of PLA in combination with the bioactivity of HA clearly provide prospective properties for resorbable bone substitute. The material, however, requires to be shaped prior to surgery, which impedes its practical use, particularly in complex shaped bone defects. In this study, a novel combination of star-shaped and linear PLA powder with various amounts of nano HA, and triethylene glycol dimethacrylate liquid was developed as an in situ forming cement for bone substitute. The effects of different amounts of initiator (0.5 and 1 wt%) and nano HA powder (5, 10, and 15 wt%) on various properties of the composite cement, including handling properties, degree of conversion, gel fraction, residual monomer toxicity and osteoblast differentiation were studied. The in vitro degradation was also examined in terms of weight and mechanical loss. The results demonstrated that the amount of initiator had a great effect on the handling properties of the cement, however, the HA content did not have any significant effect. The increasing HA content slowed down the degradation rate of the cement. All cement formulations in this study exhibited good network forming and ability to induce osteoblast differentiation with negligible residual monomer release to harm cells. The optimal cement formulation was found to be at 15 wt% HA, which allowed for in situ hardening with satisfactory biocompatibility and mechanical support for bone regeneration during deterioration.