NOVEL-APPROACH TO FABRICATE POROUS SPONGES OF POLY(D,L-LACTIC-CO-GLYCOLIC ACID) WITHOUT THE USE OF ORGANIC-SOLVENTS

A novel method was developed to produce highly porous sponges for pote ntial use in tissue engineering, without the use of organic solvents. Highly porous sponges of biodegradable polymers are frequently utilize d in tissue engineering both to transplant cells or growth factors, an d to serve as a template for tissue regeneration. The processes utiliz ed to fabricate sponges typically use organic solvents, but organic re sidues remaining in the sponges may be harmful to adherent cells, prot ein growth factors or nearby tissues. This report describes a techniqu e to fabricate macroporous sponges from synthetic biodegradable polyme rs using high pressure carbon dioxide processing at room temperature. Solid discs of poly (D,L-lactic-co-glycolic acid) were saturated with CO2 by exposure to high pressure CO2 gas (5.5 MPa) for 72 h at room te mperature. The solubility of the gas in the polymer was then rapidly d ecreased by reducing the CO2 gas pressure to atmospheric levels. This created a thermodynamic instability for the CO2 dissolved in the polym er discs, and resulted in the nucleation and growth of gas cells withi n the polymer matrix. Polymer sponges with large pores (approximately 100 mu m) and porosities of up to 93% could be fabricated with this te chnique. The porosity of the sponges could be controlled by the prefor m production technique, and mixing crystalline and amorphous polymers. Fibre-reinforced foams could also be produced by placing polymer fibr es within the polymer matrix before CO2 gas processing. (C) 1996 Elsev ier Science Limited