N-Thiolated B-lactams represent a novel family of antibacterial agents, whose in vitro activity is confined largely to Staphylococcus species, including multidrug-resistant forms of S. aureus. N-Thiolated B-lactams have recently been shown to possess intriguing biological activities which are addressed in Chapter II. Current development of nanoparticles as a new drug delivery vehicle is described in Chapter III. Chapter IV and V described the current research in our laboratories focusing on the synthesis and characterization of emulsified polyacrylate/polyacrylamide nanoparticle antibacterials for drug delivery of water-insoluble antibiotics. These nanoparticles can be prepared in aqueous media directly from acrylate/acrylamide monomers through free radical microemulsion polymerization. These emulsions contain antibiotic-conjugated polyacrylate nanospheres measuring 30-60 nm in diameter and have enhanced antibacterial activity against drug resistant S. aureus (MRSA) through what we believe is a novel mechanism.

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<p>Cancer is currently the second leading cause of death in the United States. Although many treatment options exist, some of the most common, including radiotherapy and chemotherapy, are restricted by dose-limiting toxicities. In addition, the largest hurdle for translating novel biological therapies such as siRNA into the clinic is lack of an efficient delivery mechanism to get the therapeutic into malignant cells. This work aims to improve this situation by engineering a minimally invasive controlled release system that specifically delivers therapeutics to the site of malignant tissue. This platform consists of two novel material components: a thermally responsive poly[N-isopropylacrylamide-co-acrylamide] (NIPAAm-co-AAm) hydrogel and gold-silica nanoshells. Therapeutic molecules are encapsulated within a poly(NIPAAm-co-AAm) hydrogel carrier, leading to increased serum stability, circulation time, and decreased exposure to off-site tissues. Additionally, gold-silica nanoshells embedded within this hydrogel will be used to optically trigger therapeutic release from the carrier. This hydrogel-nanoshell composite material was designed to be swollen under physiologic conditions (37 oC), and expel large amounts of water and absorbed molecules at higher temperatures (40-45 oC). This phase transition can be optically triggered by embedded gold-silica nanoshells, which rapidly transfer near-infrared (NIR) light energy into heat due to the surface plasmon resonance phenomena. NIR light can deeply penetrate biological tissue with little attenuation or damage to tissue, and upon exposure to such light a rapid temperature increase, hydrogel collapse, and drug expulsion will occur. Ultimately, these drug-loaded hydrogel-nanoshell composite particles would be injected intravenously, passively accumulate in tumor tissue due to the enhanced permeability and retention (EPR) effect, and then can be externally triggered to release their therapeutic payload by exposure to an external NIR laser. This dissertation describes the synthesis, characterization, and validation of such a controlled therapeutic delivery platform.</p><p>Initial validation of poly(NIPAAm-co-AAm)-gold nanoshell composites to act as a material in site-specific cancer therapeutic delivery was accomplished using bulk hydrogel-nanoparticle composite disks. The composite material underwent a phase transition from a hydrated to a collapsed state following exposure to NIR light, indicating the ability of the NIR absorption by the nanoshells to sufficiently drive this transition. The composite material was loaded with either doxorubicin or a DNA duplex (a model nucleic acid therapeutic), two cancer therapeutics with differing physical and chemical properties. Release of both therapeutics was dramatically enhanced by NIR light exposure, causing 2-5 fold increase in drug release. Drug delivery profiles were influenced by both the molecular size of the drug as well as its chemical properties. </p><p>Towards translation of this material into in vivo applications, the hydrogel-nanoshell composite material was synthesized as injectable-sized particles. Such particles retained the same thermal properties as the bulk material, collapsing in size from ~330 nm to ~270 nm upon NIR exposure. Furthermore, these particles were loaded with the chemotherapeutic doxorubicin and NIR exposure triggered a burst release of the drug payload over only 3 min. In vitro, this platform provided increased delivery of doxorubicin to colon carcinoma cells compared to free-drug controls, indicating the irradiated nanoshells may increase cell membrane permeability and increase cellular uptake of the drug. This phenomena was further explored to enhance cellular uptake of siRNA, a large anionic therapeutic which cannot diffuse into cells easily. </p><p>This work advances the development of an injectable, optically-triggered delivery platform. With continued optimization and in vivo validation, this approach may offer an novel treatment option for cancer management.</p> / Dissertation

An outstanding challenge in modern medicine is the safe and efficient delivery of drugs. One approach to improve drug delivery yield and increase specificity towards diseased cells, is to employ a drug carrier to facilitate transport. Promising steps towards developing such a carrier have been taken by the nascent field of nanomedicine: nanometer-sized particles designed to evade premature excretion, non-specific absorption, and the body’s immune response, can reduce undesired drug loss, while also increasing specific drug uptake into diseased cells through targeting surface modifications. However, progress is limited by incomplete knowledge of the ‘ideal’ nanoparticle design as well as a lack of appropriate high resolution construction methods for its implementation. DNA origami, a modular, nanometer-precise assembly method that would enable the rapid testing of particle properties as well as massively parallel fabrication, could provide an avenue to address these needs. In this thesis, I employed the DNA origami method to investigate how nanoscale shape and ligand functionalization affect nanoparticle uptake into cultured endothelial cells. In the first part, I evaluated the uptake yield of a series of eight shapes that ranged from 7.5 nm to 400 nm in their individual dimensions. The best performing shape of that study, a 15 × 100 nm DNA origami nanocylinder, was internalized 18-fold better than a dsDNA control of the same molecular weight. In a follow up study, I decorated this nanocylinder with integrin-targeting cyclic RGD peptides. This surface functionalization increased cellular uptake another 13-fold. In addition, uptake yield and the ratio of internalized versus surface-bound particles depended on the number of ligands present on the nanoparticle surface. This work represents a significant first step towards attaining the ability to design and implement an 'ideal' nanoparticle drug carrier. In the future, the DNA origami method can be used as a platform technology to further expand our understanding of transport properties of drug carriers and achieve safer and more efficient drug delivery.

Pancreatic cancer remains a major unsolved health problem, with conventional cancer treatments having little impact on disease course. The objective of this thesis is to create innovative tools to better understand and improve chemotherapeutic treatment of pancreatic cancer. Towards this end, nanosystems were designed with a dual purpose: to carry chemotherapeutic drugs and act as photoacoustic imaging contrast agents. The overarching hypothesis is that these nanosystems can provide enhanced therapy for pancreatic cancer and enable visualization of drug delivery. Demonstrated in this dissertation is the design, synthesis, and characterization of two such nanosystems built to carry the chemotherapeutic agent gemcitabine while acting as a photoacoustic imaging contrast agent. The nanosystems were also shown to be multifunctional with possible application as photothermal therapy agents and cellular functional sensors. Although future research is required to fully investigate the clinical potential of these systems for pancreatic cancer, the work presented in this dissertation is a step towards creation of multifunctional nanosystems that will enable non-invasive, in vivo photoacoustic imaging of drug delivery. / text

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My PhD research involves multi-disciplinary areas of study such as measuring perfusion of blood vessels in hamster dorsal skin using laser speckle imaging technique. In this study the changes were measured in blood flow velocity and diameters of micro vasculatures after the influence of glycerol application. The second study identifies the changes in morphology and optical properties of eye tissue after applying hyper-osmotic agent such as 100% anhydrous glycerol. Further investigation on the reversal process was performed without any application of 0.9% saline. The third study identified the variation in fluorescence in hamster dorsal skin tissue and enucleated porcine eyes with temperature. This study investigated the variation in fluorescence intensity with temperatures starting at 14°C and compared in vivo and in vitro results for consistency. The fourth study investigated an implantable drug delivery package that was fabricated using PMMA and implanted between the sub-conjunctival and super-scleral space and release the content of the device by either mechanical pressure or light-activated ophthalmic Nd:YAG laser after optically clearing the eye tissue by topical application of a hyper-osmotic agent, 100% anhydrous glycerol. A hyper-osmotic agent creates a transport region in the conjunctiva and sclera to get visual access of the compartments in the drug delivery package. This new technology would provide the option to the patient of one time implantation of the carrier system containing the drug. Each time the patient requires medication a ND-YAG or other laser beam will propagate through the cleared eye tissue to release the drug in measurable doses at the discretion of the doctor from the package directly in to the vitreous humor. In this study we have measured half-life of the dye in the vitreous humor or posterior chamber and biocompatibility. The last study had drawn distinction between the fluorescence signals based on the location (anterior or posterior chamber) of the 10% Na fluorescence dye in the in vivo rabbit and ex vivo pig eyes. / text