title: Synthesis of Maleimide-End Functionalized Star Polymers and Multimeric Protein-Polymer Conjugates.
abstract: Protein-polymer conjugates exhibit superior properties to unmodified proteins, generating a high demand for these materials in the fields of medicine, biotechnology, and nanotechnology. Multimeric conjugates are predicted to surpass the activity of monomeric conjugates. Herein, we report a straightforward method to synthesize multimeric polymer-conjugates. Four armed poly(N-isopropylacrylamide) (pNIPAAm) was synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization in the presence of a tetra-functionalized trithiocarbonate chain transfer agent (CTA). The polymer molecular weight, architecture and polydispersity index (PDI) were verified by gel permeation chromatography (GPC), dynamic light scattering gel permeation chromatography (DLS-GPC), and matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry. This approach afforded well-defined polymers (PDI's < 1.06) and the ability to target various molecular weights. Maleimide functional groups were introduced at the chain ends by heating the polymers in the presence of a furan-protected azo-initiator. This allowed for site-specific conjugation of V131C T4 lysozyme to the polymers to generate multimeric protein-polymer conjugates. MALDI-TOF mass spectrometry, electrospray ionization gas-phase electrophoretic-mobility macromolecule analysis (ESI-GEMMA), gel electrophoresis, and liquid chromatography tandem mass spectrometry (LC-MS/MS) of the trypsin digests demonstrated that multimeric protein-polymer conjugates had formed. This simple strategy provides ready access to star protein-polymer conjugates for application in the fields of drug discovery, drug delivery, and nanotechnology.
authors.affiliation: Department of Chemistry and Biochemistry, California NanoSystems Institute, and Department of Biological Chemistry, David Geffen School of Medicine, University of California, Los Angeles, CA 90095.
authors.forename: Lei
authors.initials: L
authors.lastname: Tao
authors.forename: Catherine S
authors.initials: CS
authors.lastname: Kaddis
authors.forename: Rachel R Ogorzalek
authors.initials: RR
authors.lastname: Loo
authors.forename: Gregory N
authors.initials: GN
authors.lastname: Grover
authors.forename: Joseph A
authors.initials: JA
authors.lastname: Loo
authors.forename: Heather D
authors.initials: HD
authors.lastname: Maynard