this invention pertains to a sustained release complex of one or more peptides , one or more proteins or a combination thereof immobilized on an absorbable polymer microparticle optionally having an absorbable polymer coating . the microparticle complex of this invention comprises a peptide and / or protein which have at least one amino group and / or at least one carboxyl group per molecule and a solid absorbable polyester microparticle having surface and subsurface carboxylic group or amino groups in sufficient amounts to bind the peptide and / or protein so that the immobilized peptide or protein represent 0 . 1 % to 30 % of the total mass of the microparticle complex . the microparticle complex with immobilized peptide and / or protein are optionally further encased individually or in groups with an absorbable polymer to control , further , the release of the immobilized peptide and / or protein . to control the release of the immobilized peptide and / or protein even further , the encased microparticles can be incorporated into a composition with an absorbable gel - forming liquid that transforms to a flexible gel or semi - solid upon contacting water in the biologic environment .