Versatility of biodegradable biopolymers: degradability and an in vivo application

Biodegradable materials have various important applications in the biomedic al field. There are basically two groups of polyesters which have significa nt importance in this field. These are polylactides and polyhydroxybutyrate s. Both groups degrade via hydrolysis with the rates of degradation dependi ng on medium properties such as pH, temperature, solvent and presence of bi ocatalysts, as well as on chemical compositions. In order for these biomate rials to be suitable for use in load bearing applications without deformati on or warping their strengths and their capability to maintain their form m ust be improved. To insure dimensional stability during degradation and to match modulus and strength to that of bone, introduction of a reinforcing s tructure for those applications to plate fixation through the creation of a n interpenetrating network might be a feasible approach. In this study, pol y(lactide-co-glycolide) (PLGA), was the major structural element to be stre ngthened by a three-dimensional network or 'scaffold' of another biodegrada ble polymer, poly(propylene fumarate) (PPF). PPF would be crosslinked with a biocompatible vinyl monomer, vinylpyrrolidone (VP). Three different appro aches were tested to create dimensionally stable bone plates. First, via in situ crosslinking of PPF in the presence of PLGA. Secondly, by blending of precrosslinked PPF with PLGA. Finally, by simultaneous crosslinking and mo lding of the PLGA, PPF and VP. These were compared against extruded or comp ression molded PLGA controls. Results showed that compression molding at ro om temperature followed by crosslinking under pressure at elevated temperat ure and subsequently by gamma -irradiation appeared to yield the most favor able product as judged by swelling, hardness and flexural strength data. Th e composition of the implant material, PLGA(3):PPF(1):VP(0.7), appeared to be suitable and formed the compositional and procedural basis for in vivo b iocompatibility studies. (C) 2001 Elsevier Science B.V. All rights reserved .