Controlled release of microquantities of macromolecules.

A technique for insuring the controlled release of small amounts of macromolecules such as polypeptides from polymeric delivery systems is described. We show that incorporation of albumin in milligram quantities into these delivery systems can facilitate the sustained release of nanogram or microgram quantities of a model macromolecule such as inulin. The albumin-containing controlled-release polymers did not cause inflammation or tissue damage in two commonly used assay sites for certain biological growth factors such as tumor angiogenesis stimulators and inhibitors--the chick chorioallantoic membrane (CAM) and the rabbit cornea. The method reported here should be particularly suited to the delivery of purified growth factors which are active and usually obtainable in microgram or smaller amounts.