(13e) Processing and Characterization of a Highly Bioactive Bone Fixation Device

Biomedical composite materials are gaining more and more interest due to their ability to integrate into the body and their success in clinical practice. Poly(lactide-co-glycolide) (PLGA) as a resorbable and degradable implant material allow avoiding a subsequent operation and postoperative stress. PLGA can be made highly bioactive [1] by incorporation of amorphous tricalcium phosphate (ATCP). This filler enables fast connection of the composite to bone. In this work [2] we use earlier experience of production of bioactive PLGA/ATCP films [3] to manufacture compact shapes i.e. blocks and screws by extrusion. The in vitro bioactivity was monitored by scanning electron microscopy (SEM) and X-ray diffraction. Furthermore, the degradation of PLGA at different time points (processing and in vitro degradation) was investigated with gel permeation chromatography. SEM images showed the homogenous dispersion of ATCP nanoparticles on the surface of the composite blocks and the induced nano-structured surface topography (Figure). The formation of an apatite layer upon immersion in simulated body fluid for PLGA/ATCP composites after 3 days was observed, confirming the in vitro bioactivity of these composites. Degradation of PLGA during different processing steps showed the highest reduction in molecular weight while applying elevated temperature and using long extrusion times. This study extends the availability of highly bioactive composites from mere films to complex shapes as required for application in oral and maxillofacial surgery. Figure: Scanning electron microscopy image of PLGA/ATCP (70/30) after extrusion (left) and bone fixation devices with and without ATCP (right). References [1] K. Rezwan, Q.Z. Chen, J.J. Blaker and A.R. Boccaccini, Biomaterials, 2006, 27, 3413-31. [2] D. Mohn, D. Ege, K. Feldman, O.D. Schneider, T. Imfeld, A.R. Boccaccini and W.J. Stark, in review. [3] S. Loher, V. Reboul, T.J. Brunner, M. Simonet, C. Dora, P. Neuenschwander and W.J. Stark, Nanotechnology, 2006, 17, 2054-61