Ethylene-vinyl acetate copolymer microspheres for controlled release of macromolecules

A simple technique has been devised for preparing ethylene-vinyl acetate copolymer microspheres containing macromolecular drugs. Beads with good sphericity were formed by a simple extrusion process that can easily be repeated by any laboratory without special equipment. The extruded droplets gelled on immediate contact with cold ethanol in a dry ice-ethanol bath. The ethanol also served to remove the solvent and harden the microspheres as they warmed to room temperature. Release of bovine serum albumin followed the expected trends, i.e., initial linearity with the square root of time and faster release rates with greater drug loading.