MANUFACTURE OF POROUS BIODEGRADABLE POLYMER CONDUITS BY AN EXTRUSION PROCESS FOR GUIDED TISSUE REGENERATION

We have fabricated porous, biodegradable tubular conduits for guided t issue regeneration using a combined solvent casting and extrusion tech nique. The biodegradable polymers used in this study were poly(DL-lact ic-co-glycolic acid) (PLGA) and poly(L-lactic acid) (PLLA). A polymer/ salt composite was first prepared by a solvent casting process. After drying, the composite was extruded to form a tubular construct. The sa lt particles in the construct were then leached out leaving a conduit with an open-pore structure. PLGA was studied as a model polymer to an alyze the effects of salt weight fraction, salt particle size, and pro cessing temperature on porosity and pore size of the extruded conduits . The porosity and pore size were found to increase with increasing sa lt weight fraction. Increasing the salt particle size increased the po re diameter but did not affect the porosity. High extrusion temperatur es decreased the pore diameter without altering the porosity. Greater decrease in molecular weight was observed for conduits manufactured at higher temperatures. The mechanical properties of both PLGA and PLLA conduits were tested after degradation in vitro for up to 8 weeks. The modulus and failure strength of PLLA conduits were approximately 10 t imes higher than those of PLGA conduits. Failure strain was similar fo r both conduits. After degradation for 8 weeks, the molecular weights of the PLGA and PLLA conduits decreased to 38% and 43% of the initial values, respectively. However, both conduits maintained their shape an d did not collapse. The PLGA also remained amorphous throughout the ti me course, while the crystallinity of PLLA increased from 5.2% to 11.5 %. The potential of seeding the conduits with cells for transplantatio n or with biodegradable polymer microparticles for drug delivery was a lso tested with dyed microspheres. These porous tubular structures hol d great promise for the regeneration of tissues which require tubular scaffolds such as peripheral nerve, long bone, intestine, or blood ves sel. (C) 1998 Elsevier Science Ltd. All rights reserved.