Bioinspired Modification of Poly(L-lactic acid)/Nano-Sized β-Tricalcium Phosphate Composites with Gelatin/Hydroxyapatite Coating for Enhanced Osteointegration and Osteogenesis

Compared to pure poly(L-lactic acid) (PLLA), PLLA/nano-sized beta-tricalcium phosphate (PLLA/n beta-TCP) composites show both superior interfacial compatibility and osteoinductive, and consequently hold great potential for bone defect repair applications. However, their dismal osteointegration limits their further development in bone regeneration, adding the need for tailored modification. In this study, a bioinspired modification approach was proposed to construct gelatin-hydroxyapatite (GEL/HAP) coating onto PLLA/n beta-TCP composites by combining chemical grafting with in situ reaction methods. The incorporation of the biomimetic GEL/HAP coating substantially improved MC3T3-E1 cell adhesion, proliferation and osteogenic differentiation, as demonstrated by morphological observation. Cell Counting Kit-8 (CCK-8) assay, alkaline phosphate activity test (ALP), and quantitative real-time polymerase chain reaction (qRT-PCR) analysis. Furthermore, GEL/HAP-PLLA/n beta-TCP composites and their control counterparts (i.e., bare PLLA/n beta-TCP) were synchronously implanted into femoral condylar defects of an identical rabbit. Characterizations including microcomputed tomography (micro-CT), histological analysis and the push-out test revealed that the biomimetic coating not only improved osteointegration but also significantly promoted bone regeneration. Overall, for the first time, bioinspired surface modification of the PLLA/n beta-TCP composite with GEL/HAP coating was demonstrated to be an efficient strategy for enhancing the osteointegration and osteogenesis functions of bone implants.