ChBE Seminar Series: James Mixson
Tuesday, October 7, 2014
11:00 a.m.-12:15 p.m.
Room 2108, Chemical and Nuclear Engineering Bldg.
Professor Jeffery Klauda
Molecular Characterization of Histidine-rich Polyplexes for Enhanced Gene Delivery
James Mixson, M.D.
Professor of Pathology
University of Maryland–Baltimore
Selection of non-viral carriers for in vivo gene delivery is frequently dependent on determining the optimal carriers from transfection assays in vitro. The rationale behind this in vitro strategy is to cast a net wide enough to identify the few effective carriers of nucleic acids for in vivo studies. Nevertheless, many effective in vivo carriers may be overlooked by this strategy because of the marked differences between in vitro and in vivo assays. We compared two histidine-lysine peptide structures, one effective (the branch H2K4b) and the other ineffective (the linear H2K) in vitro, for their ability to deliver plasmid DNA systemically to subcutaneous tumor xenografts. In contrast to their transfection activity in vitro, the linear H2K carrier of plasmids was signifiantly more effective in vivo compared to the branch H2K4b. Surprisingly, negatively charged polyplexes formed by the linear H2K peptide gave higher transfection in vivo than did those with a positive surface charge. To examine the distribution of plasmid expression within the tumor from H2K polyplexes, we found widespread expression by immunohistochemical staining. Although mechanisms underlying the efficiency of gene expression are likely multifactorial, unpacking of the H2K polyplex within the tumor may have a significant role.