Polyethylene glycol-lysine copolymers. New biocompatible polymers for biomedical applications

Unique properties of polyethylene glycol (PEG) including wide range of solubilities, lack of toxicity, absence of antigenicity and immunogenicity, non-interference with enzymatic activities and conformations of polypeptides, non-biodegradability, and ease of excretion from living organisms, all suggest that this polymer may be an ideal drug carrier. We developed an efficient method for the synthesis of water soluble polyurethanes comprised of lysine and PEG units. The properties of the new polymers are dominated by PEG, while the carboxyl groups of the lysyl residues provide convenient anchors for attachment of the appropriate pendant ligands. The distance between the reactive carboxyl groups is controlled by the size of PEG-macromonomer, and the molecular weight of the PEG-lysine copolymer can be fine-tuned by a careful choice of polycondensation conditions.