Dissertation/Thesis Abstract

Engineering nanoparticles for gene therapy and cancer therapy
by Liu, Yarong, Ph.D., University of Southern California, 2014, 168; 3628227
Abstract (Summary)

Virus-based nanoparticles have shown promise for mediating gene delivery due to their well-defined nanostructure and intrinsic bioactive functionality. Adeno-associated virus (AAV) has been considered as a promising vehicle for human gene therapy based on its ability to infect both dividing and nondividing cells, as well as establish long-term gene expression in vivo without known pathological consequence of infection. However, because of their native tropisms, the applicability of AAV nanoparticles is often limited to the restricted ranges of cells or tissues. Studies proposed that low expression of receptors/coreceptors on cell surface and an impaired intracellular trafficking pathway of vectors could be the rate-limiting steps of AAV-mediated transduction. In this study, we have developed two strategies for enhancing AAV-mediated gene delivery by overcoming these two biological barriers. The first strategy we used is generating a targeted AAV2 vector by genetically encoding an aldehyde tag on viral capsids. Such a tag can be exploited for site-specifi c attachment of targeting molecules and allows for further introduction of targeting antibodies or ligands. The results showed that the site-specific conjugation of targeting antibodies could significantly enhance viral transduction to those target cells that have otherwise exhibited very low permissiveness to AAV2 infection. This method also allows the functional incorporation of RGD peptides onto AAV2 for enhanced delivery with implications for cancer gene therapy. Another strategy we used to enhance AAV transduction, both in vitro and in vivo, is incubating AAV vectors with cell-permeable peptides (CPPs). We show that CPPs increase internalization of viral particles into cells by facilitating both energy-independent and energy-dependent endocytosis. Moreover, CPPs can significantly enhance the endosomal escape process of viral particles, thus enhancing viral transduction to those cells that have exhibited very low permissiveness to AAV2 infection as a result of impaired intracellular viral processing. We also demonstrated that this approach could be applicable to other AAV serotypes.

Non-viral based nanoparticles offers new hope for cancer detection, prevention and treatment due to their potentials to deliver drugs to tumors. Liposomes constitute one of the most popular nanocarriers for the delivery of cancer therapeutics. However, since their potency is limited by incomplete drug release and inherent instability in the presence of serum components, their poor delivery occurs in certain circumstances. In this study, we address these shortcomings and demonstrate an alternative liposomal formulation, termed crosslinked multilamellar liposomal vesicles (cMLVs). With its properties of improved sustainable drug release kinetics and enhanced vesicle stability, cMLVs can achieve controlled delivery of cancer therapeutics. We further showed that the cMLVs are potential in combination therapy by loading drugs with different hydrophilicities into the same cMLV in a precisely controllable manner over drug ratios. The stability of cMLVs allows an improved loading efficiency and sustained release of doxorubicin (Dox) and paclitaxel (PTX), maximizing the combination therapeutic effect and minimizing the systemic toxicity. Furthermore, in vivo experiments showed that the robust cMLV formulation maintains drug ratios for prolonged times, enabling the ratio-dependent combination synergy translating from in vitro to in vivo antitumor activity. We also demonstrated that this combinatorial delivery system (cMLV(Dox+PTX)) achieves enhanced drug accumulation and retention, resulting in improved cytotoxicity in tumor cells, including drug resistant cells. Moreover, cMLV(Dox+PTX) significantly overcomes MDR by reducing the expression of P-glycoprotein (P-gp) in cancer cells, thus improving antitumor activity in vivo. With a combined therapeutic ability that enhances drug delivery efficacy to tumors and lowers the apoptotic threshold of individual drugs, cMLV(Dox+PTX) represents a potential multimodal therapeutic strategy to overcome MDR in cancer therapy.

Indexing (document details)
Advisor: Wang, Pin
Commitee: Arnold, Don B., Shing, Katherine
School: University of Southern California
Department: Chemical Engineering
School Location: United States -- California
Source: DAI-B 75/11(E), Dissertation Abstracts International
Subjects: Cellular biology, Biochemistry, Biomedical engineering, Nanotechnology, Immunology, Oncology
Keywords: Adeno-associated virus, California, Combination therapy, Crosslinked multilamellar liposome, Gene delivery, Synergy, Targeted viral vector
Publication Number: 3628227
ISBN: 9781321038019
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