Tongxin Wang, Develop Bioresorbable Nanocomposites for Bone Fixation

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Bioresorbable materials are clinically desirable for bone fixation and repair, because they can eliminate the side effects from current metallic implants (e.g. possibility for second surgery to be removed after bone heals, risk for secondary bone fracture from stress-shielding effect and interference with diagnosticinstruments (e.g. CT, MRI)). A critical barrier to more successfully apply bioresorbable polylactide/calcium phosphate (PLA/CaP) composites to bone fixation, particularly for the load-bearing areas, is their weak mechanical properties. The goal of this research is to develop a new technology to improve the mechanical strength of bioresorbable PLA/CaP composites, so that they can well match those of natural bones. Because a major reason for the low mechanical strength of the composites is lack of interfacial binding between the CaP filler and PLA matrix, the proposed strategies include (1) creating a new core-shell inorganic-organic hybrid structure that employs a chelating phosphonic coupling agent, which can strongly bind with CaP fillers, and (2) combining with surface initiated polymerization technology (SIP) which can form strong chemical bonds with PLA matrix. The hypothesis is that the interfacial adhesion between PLA matrix and CaP fillers can be enhanced by the proposed technology, thus the mechanical strength of PLA/CaP composites can be significantly improved. Because DCPD (dicalcium phosphate dehydrate) has produced good clinical outcome for bone defect repair and is resorbed more rapidly than hydroxyapatite (HA) in vivo, this project will focus on using DCPD as the filler to prepare PLA/CaP composite.