UMD Theses and Dissertations

Permanent URI for this collectionhttp://hdl.handle.net/1903/3

New submissions to the thesis/dissertation collections are added automatically as they are received from the Graduate School. Currently, the Graduate School deposits all theses and dissertations from a given semester after the official graduation date. This means that there may be up to a 4 month delay in the appearance of a given thesis/dissertation in DRUM.

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    Investigation of a thiolated Polymer In Gene Delivery
    (2012) Bacalocostantis, Irene; Kofinas, Peter; Muro-Galindo, Silvia; Bioengineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Thiol-containing bioreducible polymers show significant potential as delivery vectors in gene therapy, a rapidly growing field which seeks to treat genetic-based disorders by delivering functional synthetic genes to diseased cells. Studies have shown that thiolated polymers exhibit improved biodegradability and prolonged in vivo circulation times over non-thiolated polymers. However, the extent to which thiol concentrations impact the carrier's delivery potential has not been well explored. The aim of this dissertation is to investigate how relative concentrations of free thiols and disulfide crosslinks impact a polymeric carriers delivery performance with respect to DNA packaging, complex stability, cargo protection, gene release, internalization efficiency and cytotoxicity. To accomplish this goal, several fluorescent polymers containing varying concentrations of thiol groups were synthesized by conjugating thiol-pendant chains onto the primary amines of cationic poly(allylamine). In vitro delivery assays and characterization techniques were employed to assess the effect of thiols in gene delivery.
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    PROBING BIOMECHANICAL PROPERTIES OF SINGLE MOLECULE SYSTEMS USING OPTICAL TWEEZERS
    (2011) Karcz, Adam P.; Seog, Joonil; Material Science and Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Single molecule techniques have provided novel mechanistic insights on biological processes such as protein folding, transcription, and motor protein movement. Using single molecule methods, the distribution of individual molecular behavior is directly measured, which cannot be obtained using conventional bulk approaches. In this study, custom-built optical tweezers with sub-pN force resolution were used to probe the dynamic behavior of DNA:cationic carrier complex. Two histidine-lysine (HK) based polymers (H3K4b vs H3KG4b) were used to compare their condensation behaviors at the single molecular level. The difference between the two HK polymers at the single molecule level may have a significant implication as to why H3KG4b shows much higher gene delivery efficiency than H3K4b. The optical tweezers were also used to probe the unfolding processes of a fragment of F1 RNA. This can be used to characterize secondary structures in RNA, such as hairpins and pseudoknots.
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    RNA packaging and gene delivery using Tobacco mosaic virus pseudo virions
    (2008-04-28) Hung, Chi-Wei; Bentley, William; Chemical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    RNA interference (RNAi) has emerged as a powerful tool for the study of gene function and post-transcriptional regulation. However, the lack of a proper delivery system for RNAi is a major problem for its application as a therapeutic agent. In this study, Tobacco mosaic virus (TMV) is utilized as an RNAi carrier for gene delivery into mammalian and insect cells. The self assembly and disassembly of TMV is investigated to create chimeric viruses for gene delivery. The origin of assembly sequence (OAS) within the TMV RNA initiates its association with coat protein through a unique hairpin structure. Studies in this dissertation show that by incorporating TMV OAS into an RNA of interest, the RNA can assemble into "pseudo-virions" by the virus coat protein. The length of the pseudo-virions changed in proportion with the size of the RNA. To deliver the RNA to the targeted cells, virions are further surface-modified with synthetic cell-penetrating peptides to facilitate cell endocytosis. Two genes were selected as targets: 1) EGFP as a visual marker and 2) Cyclin E for control of cell cycle. EGFP is expressed in a transient expression experiment using a plasmid vector, pEFGP-N1. Cyclin E is regulated endogenously in High FiveTM cells, and its translation is targeted using the pseudo virions. Pseudo-virions targeting EGFP RNA (antisense EGFP) are able to suppress transient EGFP production by 61% whereas pseudo virions targeting cyclin E (antisense cycE) are capable of arresting cells at G1 phase. This RNA packaging system protects packaged RNA and provides a means of delivering RNAi constructs into various host cells.