Methodologies for preparation of synthetic block copolypeptides: materials with future promise in drug delivery

This article summarizes recent developments in the synthesis of copolypeptides, focusing on the realization of living polymerizations that allow preparation of materials with excellent attributes for drug delivery. Traditional methods used to polymerize alpha-amino acid-N-carboxyanhydrides (NCAs) are described, and limitations in the utility of these systems for the preparation of polypeptides are discussed. A system utilizing transition metal catalysis for polypeptide synthesis is described that allows preparation of materials that begin to rival biologically produced counterparts in terms of complexity and purity. Overall, new developments in NCA and beta-lactam polymerizations hold tremendous promise now that block copolypeptides of controlled dimensions (molecular weight, sequence, composition, and molecular weight distribution) can be prepared. Such well-defined polymers should greatly assist in the development of new drug carriers with increased function.