Tissue Response to Citric Acid-Based Micro-/Nanocomposites

INTRODUCTION: There is significant demand for orthopaedic implants that are both bioactive and exhibit material properties that are compatible to those of native and healthy tissue [1]. Synthetic materials play an important role in bone repair and bone replacement. In the case of poly (L-lactide) (PLLA), one of the main problems is slow degradation, which further spark tissue loss due to revision surgeries and chronic inflammation [2, 3]. Recently, a novel elastomer poly (1, 8-octanediol-co-citrate), or POC, has been developed in our group. In particular, POC has a fast degradation rate (6 months to 1 year) and display good biocompatibility with soft tissue. The degradation and mechanical properties can be controlled by varying the polymerization conditions (time and temperature) and the choice of diols. In addition to its clinical compatibility, POC synthesis is simple, does not involve harsh solvents or catalysts, and is cost effective. Recently, we have developed POChydroxyapatite composites which have controllable mechanical properties and degradation rates [4]. POC-HA is malleable to meet the need of various irregular shapes of bone defects and is easily processed into a hard implant. In this study, POC composites were developed with hydroxyapatite (HA) nanocrystals and microparticles and implanted into the rabbit knee to assess biocompatibility. Because bone is composed of apatite nanocrystals, the hydroxyapatite nanocrystals having the same constituent and structure of bone may lead to engineered tissue closely resembling native tissue. Both POC nanoand micro-HA are physiologically compatible, but exhibit differences in vivo