We have developed a novel technique to synthesize near-uniform protein-polymer conjugates by initiating atom transfer radical polymerization of monomethoxy poly(ethylene glycol)-methacrylate from 2-bromoisobutyramide derivatives of chymotrypsin (a protein-initiator). Polymerization initiated from the monosubstituted protein-initiator resulted in the conjugate containing a single, near-monodisperse polymer chain per protein molecule with polydispersity index 1.05. Increasing the number of conjugated 2-bromoisobutyramide initiators per molecule of protein increased the molecular weights and polydispersity indices of the final protein-polymer conjugates. The generic nature of this technique was demonstrated by initiating polymerization of nonionic, cationic, and anionic monomers from the protein-initiator. Protein-polymer conjugates synthesized by this novel technique retained 50-86% of the original enzyme activity. The technique described herein should be useful in synthesizing well-defined protein-polymer conjugates exhibiting a wide range of physical and chemical properties.

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Two novel A-B-A type amphiphilic triblock copolymers, namely poly(N-(2-hydroxypropyl)-methacrylamide)-block-poly( -caprolactone)-block-poly(N-(2-hydroxypropyl)methacrylamide) (PHPMA-b-PCL-b-PHPMA) and poly(N-vinyl-2-pyrrolidone)-block-poly( -caprolactone)-block-poly(N-vinyl-2-pyrrolidone) (PVP-b-PCL-b-PVP), were synthesized and characterized. These polymers were prepared by free radical polymerization of N-(2-hydroxypropyl)methacrylamide and N-vinyl-2-pyrrolidone in the presence of a novel biodegradable, macromolecular chain-transferring agent, R,ω-poly( -caprolactone) dithiol (HS-PCL-SH). All triblock copolymers self-assembled in aqueous solutions to form supramolecular aggregates of 30-200 nm size. The critical aggregation concentration of the polymers ranged from 1 to 4 mg/L. The partition equilibrium constant (K v) of pyrene in the hydrophobic core of micelles was comprised between 2.5 × 10 5 and 4.2 × 10 5 . The triblock copolymer micelles were loaded by a dialysis procedure with 1-4% (w/w) of two model poorly water-soluble drugs, i.e., doxorubicin and amphotericin B. These triblock copolymers could prove useful as nanocarriers for the solubilization and transport of hydrophobic drugs. The bifunctional macromolecular chain-transferring agent reported in this work can also find application in the synthesis of a variety of novel A-B-A type biodegradable triblock copolymers.