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Characterization of various polymer materials for biomedical application and gene therapies


NSF-funded researchers, Dr. Tim Long (Chemistry), Dr. Theresa Reineke (Chemistry), Webster Santos (Chemistry), Padma Rajagopalan (Chemical Engineering), and Dr. Richie Davis (Chemical Engineering) with MILES-IGERT trainees Rebecca Brown (a recent graduate, December 2009), Matt Green, Mike Allen are continuing the synthesis of polymers and peptide sequences for various biomedical applications. Rebecca successfully developed and characterized charged polymers with both positive and negative charges. These polymers formed membranes that mimic those in biological systems and are used as antimicrobial agents. Matt and Mike are continuing their work on polymer development for gene therapy.

Specifically, Matt Green and Mike Allen have been working on the synthesis and characterization of imidazole-based molecules for gene and drug delivery. Recent research efforts have focused on interdisciplinary, collaborative projects that incorporate antioxidants into potential nonviral gene delivery vectors. Synthetic nonviral gene delivery vectors are polymers prepared in Dr. Long’s laboratory that can effectively chaperone nucleic acids, including DNA, into the cell nucleus of infected cells. Upon delivery, the therapeutic DNA repairs defective genetic sequences responsible for diseases such as cystic fibrosis or sickle cell anemia. The vectors focused upon in these experiments possess the imidazole ring, the pendant functional group of the amino acid histidine, and were prepared and functionalized with glutathione, a common antioxidant compound. Upon delivery to the cell, enzymes in cellular space cleave the glutathione, which releases the oxidized glutathione that can protect against reactive, oxidative species.

This approach was partly considered due to the oxidative stress imparted upon the cell through delivery of foreign materials, even those therapeutic in nature. The complex of polymer and DNA upon entry into the cell, initiate a series of events that could potentially damage or harm the cell by oxidative means. Therefore, the glutathione-conjugated polymer, upon delivery within the cell will release oxidized glutathione. The oxidized glutathione upon exposure to oxidative species, including reactive oxygen species (ROS) will cleave from the polymer and inhibit cell damage from ROS. Both MILES-IGERT trainees have looked at toxicities and transfection efficiencies of the polymers they have synthesized.

Address Goals

Gene therapy is an active field of study because of the potential for treatment of a variety of genetic disorders. Understanding the formation, size, charge, composition, and dissociation of polyplexes will lead to the understanding of delivery mechanisms which can provide information about for designing therapeutic drugs or antioxidants. Understanding the mechanisms of transfection of cells using antioxidant materials protected by charged macromolecules presents possibilities for engineering therapies. Successful polyplex formation and delivery using novel substituted poly(1-vinylimidazole) polymers has been achieved. Mike and Matt are synthesizing a series of novel imidazolium monomers for future studies to better understand the structure property relationships associated with gene delivery. These projects will significantly contribute to the biological field in terms of transfection and cytotoxicity. These projects take the chemistry behind these polymers in order to provide a better understanding of structure-transfection efficiency.