Insulin-albumin microbeads: an implantable, biodegradable system.

A feasibility study on developing an implantable, biodegradable insulin delivery system was carried out. Insulin-albumin microbeads (50-1,000 microns diameter) were implanted in diabetic rats. After a single subcutaneous implant of the glutaraldehyde crosslinked microbeads, elevated blood-insulin levels were detected in the diabetic animals for longer than two months. While the blood-insulin levels of the treated animals were sustained between 10 and 67 microU/ml during the initial two month post-implantation period, complete in-vivo biodegradation of the microbeads took longer than five months. The diabetic animals, with the insulin-albumin microbead implants, gained weight. In contrast, untreated diabetic controls lost weight. Fibrous capsules were found to have surrounded the microbeads when the implants were recovered at one and two months post-implantation. The results suggest that the fibrous capsules played a role in retarding insulin release from the albumin microbead system. Cross-linked serum albumin microbeads have the clinical potential of providing long-term in-vivo drug release. This system has the additional advantage of being biodegradable and also provides more options for the method and site of implantation.