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Development and Biophysical Characterization of HK Polymer for siRNA Delivery to Tumor in a Mouse Model

dc.contributor.advisorMixson, Archibald Jen_US
dc.contributor.advisorSeog, Joonilen_US
dc.contributor.authorChou, Szu-Tingen_US
dc.date.accessioned2014-06-26T05:35:14Z
dc.date.available2014-06-26T05:35:14Z
dc.date.issued2014en_US
dc.identifier.urihttp://hdl.handle.net/1903/15448
dc.description.abstractDelivery has been the major obstacle for nucleic acid therapeutics, including the RNA interference (RNAi) approach. Mixson's lab has been focused on the development of a non-viral peptide-based delivery system, HK (histidine-lysine) polymers, which have shown promise as carriers of plasmids and small interference RNA (siRNA) in several cell lines and in tumor-bearing models. In a previous study, a four-branched peptide, denoted H3K(+H)4b, with the predominant repeating -HHHK- sequence in the branch, has been shown to be the most effective and least toxic carrier <italic>in vitro</italic> and <italic>in vivo</italic>. Building on these results, I utilized different approaches including several structure and stability molecular characterization methods to study polyplex and to develop more effective carriers for improved therapy with siRNAs targeting malignancies. To understand the role of histidine in the stability of the H3K(+H)4b/siRNA polyplex, the physicochemical properties were investigated. With the use of isothermal titration calorimetry and heteronuclear single quantum coherence NMR, histidines were shown to form hydrogen bonds with siRNA, which enhanced the stability and biological activity of the polyplexes. In addition, to enhance resistance to nucleases and to target the tumors selectively, H3K(+H)4b was chemically modified with different patterns of polyethylene glycol (PEG) and cyclic RGD (Arg-Gly-Asp, cRGD) peptide conjugates. The luciferase marker gene expressed stably by tumor xenografts in mouse models was targeted in order to evaluate the efficacy of HK carriers of siRNA that differed in location and number of cRGD-PEG attachments. The most effective carrier was (RGD-PEG)<super>4</super>H3K(+H) (RP-HK), which has a cRGD-PEG on each of its four terminal branches. Consistent with its prolonged stability, as observed by pharmacokinetic studies, the RP-HK polyplex down-regulated luciferase activity in tumor xenografts by nearly 70% compared with the untreated group. Subsequently, the RP-HK polyplex was used to target the Raf-1 oncogene, an important mediator of tumor cell growth and angiogenesis. As in the luciferase studies, the polyplex reduced Raf-1 mRNA by more than 75%, and more importantly, the treatment inhibited the tumor growth by 60% in a mouse model. We anticipate that further design and engineering of HK carriers will improve the predictability and therapeutic activity of siRNA polyplexes in cancer treatment.en_US
dc.language.isoenen_US
dc.titleDevelopment and Biophysical Characterization of HK Polymer for siRNA Delivery to Tumor in a Mouse Modelen_US
dc.typeDissertationen_US
dc.contributor.publisherDigital Repository at the University of Marylanden_US
dc.contributor.publisherUniversity of Maryland (College Park, Md.)en_US
dc.contributor.departmentChemical Engineeringen_US
dc.subject.pqcontrolledBiomedical engineeringen_US
dc.subject.pqcontrolledChemical engineeringen_US
dc.subject.pqcontrolledMaterials Scienceen_US
dc.subject.pquncontrolledCanceren_US
dc.subject.pquncontrolledGene deliveryen_US
dc.subject.pquncontrolledHK peptideen_US
dc.subject.pquncontrolledNon-viral carrieren_US
dc.subject.pquncontrolledsiRNAen_US


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