CONTROLLED-RELEASE OF ALBUMIN FROM BIODEGRADABLE POLY(DL-LACTIDE) CYLINDERS

A cylindrical monolithic matrix release device was made by extruding a n albumin suspension in a poly(DL-lactide) acetone solution, to form r ods. After coating with pure poly(DL-lactide), the rods, with 10% to 3 0% albumin loading, were cut into specific lengths (0.5-4 cm). The rel ease properties of protein from short cylinders (0.5-1 cm, 30% loading ) into saline were found to be primarily diffusion controlled. Albumin was released from channels which were formed by voids originally pres ent and voids left by released albumin, all connected to the uncoated ends of the cylinder. On the other hand, the release of albumin from l onger devices (2-4 cm, 30% loading) was controlled by a combination of diffusion and osmotic pressure. The effect of device manufacturing fa ctors (i.e., poly(DL-lactide) solution concentration and polymer molec ular weight), on the release properties was not found to be significan t. When the loading was reduced from 30% to 10%, for the short cylinde rs, the release mechanism changed from diffusion controlled to osmotic pressure controlled. It was possible to adjust the release rates by c utting the cylinders into different lengths. For devices of 0.5 to 4 c m in length and 30% loading, the duration of release went from 200 to 800 hours, respectively.