Conjugation approach of drug to biodegradable poly(D,L-lactic-CO-glycolic acid) for controlled release from microspheres

A new approach of controlled release of two hydrophilic model drugs, lysozyme and protected tryptophan (Fmoc-Trp(Boc)), from poly(D,L-lactic-co-glycolic acid) [PLGA] microspheres was attempted. The novel formulation strategy is based on the hypothesis that lysozyme can not be released from microspheres until the PLGA polymer chain gradually degrades and reaches to a critical molecular weight at which the water solubility of lysozyme-PLGA oligomer conjugate is sufficiently gained. The drug-PLGA conjugates were formulated into microspheres by a single O/W emulsion method. The drug release kinetic behaviors from the conjugated drug loaded microspheres were compared with those from the conventional unconjugated drug loaded microspheres.