Interfacial and Mechanical Improvement of Bioresorbable Polylactide-Calcium Phosphate Composites

T. Wang, Q. Dong, L.C. Chow, M. Yang, J.W. Mitchell
Howard University, US

Keywords: bioresorbable, polymer composite, interface, bone repair, mechanical property

Summary:

Bioresorbable composites are desirable for bone repair, because they do not have to be removed after bone heals and have no interference with diagnostic instruments such X-ray and MRI imaging. Two obstacles of bioresorbable polylactide (PLA) / calcium phosphate (CaP) composites preventing their successful application particularly to the load-bearing location are the weak mechanical properties and unsatisfactory biocompatibility. This project developed two strategies to coat the surface of CaP particles, so that the interfacial adhesion and mechanical properties can be improved. While one strategy is to develop a core-shell hybrid structure combined with surface initiated polymerization, the other is to combine the functionalized silane coupling agent with surface protonation of CaP. Thus, more silane and PLA can be grafted on the surface of CaP, leading to strong interface. Consequently, the tensile strength of PLA/HA (hydroxyapatite) composite has been improved in around 100%. In addition, a new filler, TTCP (tetracalcium phosphate), was incorporated into the polymer, thus the biocompatibility could be improved. The tensile strength of the PLA/TTCP composite was successfully improved to 70 MPa, which well matches with that of natural bone and may allow them to be used to the load-bearing location.