Interface Control of Poly(L-lactic Acid)/Hydroxyapatite Composites by Using Bisphosphonate

Poly(L-lactic acid)/hydroxyapatite (PLLA/HAp) composites have attracted significant attention as environmentally friendly tough materials due to their excellent biocompatibility and mechanical strength. However, the poor organic–inorganic interfacial adhesion between PLLA and HAp has been a significant challenge, often resulting in the premature elution of PLLA and a reduction in the mechanical integrity. Here, we prepared PLLA/HAp composites with a controllable interface by using etidronic acid, a bisphosphonate compound, as an interface modifier for HAp. Etidronic acid modification of HAp increased the bending strength of PLLA/E-HAp composites up to 66.7 MPa and improved the stability in phosphate buffer saline solution due to grafting of PLLA chains onto the HAp surface. The interface strengthened by chelation between etidronic acid and Ca in HAp could be dissociated in hydrochloric acid, resulting in the successful separation of PLLA and HAp.