ABSTRACT
In 1976, Langer and Folkman pioneered the sustained release of protein molecules from biocompatible hydrophobic polymers (1). Further work by Rhine et al. refined the techniques for fabricating polymer matrices for the sustained release of very water soluble proteins such as albumin (2). These polymeric delivery systems were ultimately used to deliver therapeutic proteins such as insulin (3-6). However, insulin represented a somewhat different macromolecule from those that had been studied before. Insulin’s aqueous solubility was much lower than that of albumin, and its release kinetics were slower than what had been observed for more water soluble proteins like albumin. Thus the research efforts in developing a sustained release insulin delivery system became a study in the solubility properties of insulin.
