Palmitic acid-modified poly-L-lysine for non-viral delivery of plasmid DNA to skin fibroblasts
ABSTRACT Palmitic acid conjugates of poly-L-lysine (PLL-PA) were prepared, and their ability to deliver plasmid DNA into human skin fibroblasts was evaluated in vitro. The conjugates were capable of condensing a 4.7 kb plasmid DNA into 50-200 nm particles (mean +/- SD = 112 +/- 34 nm), which were slightly smaller than the particles formed by PLL (mean +/- SD = 126 +/- 51 nm). Both PLL and PLL-PA were readily taken up by the cells, but PLL-PA delivered the plasmid DNA into a higher proportion of cells. DNA delivery was found to be reduced by endocytosis inhibitor Brefeldin A, suggesting an active mechanism of particle uptake. Using enhanced green fluorescent protein (EGFP) as a reporter gene, PLL-PA was found to give the highest number of EGFP-positive cells among several carriers tested, including polyethyleneimine, Lipofectamine-2000, and an adenovirus. Although some carriers gave a higher percentage of EGFP-positive cells than PLL-PA, they were also associated with higher toxicities. We conclude that PLL-PA is a promising gene carrier for non-viral modification of human fibroblasts.
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ABSTRACT: The delivery of growth factors has been attempted for a number of different therapies. The approach of delivering therapeutic growth factors in a safe and efficient manner is difficult and certain criteria should be met. These criteria include: binding the appropriate growth factors, maintaining their bioactivity, and delivering these proteins with controllable release kinetics for an extended period of time. These criteria encompass a set of guidelines that hope to mimic in vivo biological events such as neovascularization. The central goal of this thesis is to meet these criteria by introducing a novel delivery strategy for growth factors using a biocompatible polycation and heparin. It was hypothesized that a polycation could interact with heparin to form a complex with the potential to deliver bioactive growth factors with an adaptable release. This hypothesis was tested by examining the release kinetics of bFGF from the complex and investigating whether the released bFGF maintained its bioactivity. The [polycation:heparin:bFGF] complex was formed by mixing the components in water, resulting in a precipitate. This precipitate was able to deliver bFGF with controllable release kinetics and the bioactivity of the released bFGF was higher than bolus bFGF and comparable to heparin stabilized bFGF. This system is expected to have the ability to bind and deliver numerous heparin-binding growth factors. In conclusion, the delivery system developed in this research provides a novel mechanism for controlled release of growth factors. This delivery strategy has met the criteria listed earlier and this research has laid the foundation for a successful delivery vehicle. Further, a biocompatible polycation was synthesized, which is a critical component of the delivery system. This polycation exhibited in vitro and in vivo biocompatibility that was orders of magnitude higher than existing polycations and has the potential to be very useful in a variety of biomedical applications. This design principle is also expected to serve as a platform for the synthesis of other biocompatible polycations. Ph.D. Committee Chair: Wang, Yadong; Committee Member: Barker, Thomas; Committee Member: Boyan, Barbara; Committee Member: Chaikof, Elliot; Committee Member: Meredith, J. Carson; Committee Member: Prausnitz, Mark
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Conference Paper: Millimeter wave dielectric measurements at elevated temperatures[Show abstract] [Hide abstract]
ABSTRACT: Interest in the constitutive parameters of materials at elevated temperatures continues to increase as new materials are developed for high-temperature applications. A simple, relatively nondestructive method for testing materials at millimeter wave frequencies is presented here. Measurements have been performed between 30 and 100 GHz at temperatures up to 1500°C in a commercially available furnace. Measurements to date have been performed on dielectric materials with dielectric constants ranging from 1.2 to 10. The measured dielectric constant and loss tangent of a low-loss foam material are shownAntennas and Propagation Society International Symposium, 1991. AP-S. Digest; 07/1991