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Protein-Polymer Nanomaterials for Therapeutic Applications


Protein-polymer hybrid nanomaterials, designed for the targeted delivery of therapeutic anti-cancer agents, are at the forefront of research in biotechnology, nanotechnology, and cancer therapy. Conventional chemotherapeutics exhibit non-specific toxicity due to broad biodistribution; therefore developing nano-sized drug delivery vehicles for the targeted delivery of chemotherapeutics to tumors and cancer cells is important. Nanoparticles (ranging from 10-100 nanometers in size) accumulate in solid tumors and can be functionalized in order to encapsulate therapeutics and target cancer cells. Herein, the development of two classes of protein-polymer nanomaterials is described.

Vaults are naturally occurring protein-cages measuring 42 x 42 x 75 nm in dimension with a hollow internal cavity. Vaults are non-immunogenic, readily expressed, and can be engineered. We have developed stimuli responsive vault-polymer conjugates. A protein reactive thermo-responsive poly(N-isopropylacrylamide) was prepared via reversible addition-fragmentation chain transfer (RAFT) polymerization and conjugated to the vault, resulting in a thermo-responsive vault nanoparticle (Chapter 2). Dual responsive vault nanoparticles have also been developed via conjugation of a pH- and thermo-responsive polymer, poly(N-isopropylacrylamide-co-acrylic acid), prepared by RAFT polymerization (Chapter 3).

The design of nanoparticles was further explored by conjugating proteins to disulfide cross-linked poly(poly(ethylene glycol) methyl ether methacrylate) (pPEGMA) nanogels. Thiol-reactive nanogels were conjugated to thiol-enriched proteins via a simple disulfide exchange reaction (Chapter 4).

Additionally, the development of new methods for protein-polymer conjugation is described. Ring opening metathesis polymerization (ROMP) was used for the preparation of protein-reactive unsaturated poly(ethylene glycol) (PEG) analogs (Chapter 5). These unsaturated PEG analogs were conjugated to proteins. Due to olefins present in the polymer backbone, the polymer can be degraded from the conjugated protein by exposure to Grubbs type metathesis catalysts. Furthermore, a ROMP grafting from approach has also been developed, whereby the protein streptavidin (SAv) was functionalized with a biotinylated ruthenium metathesis catalyst. The SAv macrocatalyst was then used in the ROMP of a tetraethylene glycol modified norbornene monomer to yield a well defined protein-polymer conjugate (Chapter 6).

Lastly, the preparation of a telechelic, protein-reactive polymer by RAFT polymerization is described (Chapter 7). A Boc-protected aminooxy RAFT chain transfer agent (CTA) was synthesized and utilized in the polymerization of poly(ethylene glycol) methyl ether acrylate (PEGA). The resulting aminooxy functionalized pPEGA was then functionalized post-polymerization to install cysteine-reactive vinyl sulfone functionality on the polymer.

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