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TARGETED AND SUSTAINED DELIVERY OF POLYPHOSPHATE FOR SUPPRESSION OF BACTERIAL COLLAGENASE AND POST-SURGICAL INTESTINAL HEALING
Title
TARGETED AND SUSTAINED DELIVERY OF POLYPHOSPHATE FOR SUPPRESSION OF BACTERIAL COLLAGENASE AND POST-SURGICAL INTESTINAL HEALING
Creator
Nichols, Dylan
Date
2018, 2018-05
Description
Nanoparticle drug delivery holds great promise in the field of nanomedicine. Nanoparticles, containing encapsulated drugs, provide a variety...
Show moreNanoparticle drug delivery holds great promise in the field of nanomedicine. Nanoparticles, containing encapsulated drugs, provide a variety of advantages for administration of therapeutic factors including controlled and sustained drug release and site-specific targeting thereby improving therapeutic efficacy. At the forefront of modern medicine is the onset of understanding how an individual’s microbiome may impact their health and how to avoid upsetting this sometimes delicate but often essential ecosystem. The human gastrointestinal tract is subject to a variety of physiological perturbations as a result of disease or surgical interventions that lead to major disturbances in gut microbial ecology. Furthermore, administration of antibiotics to address these issues have been shown to exacerbate the intestinal dysbiosis and create local cues that shift the composition and function of the normal microbiota to a state in which certain strains become dominant and pathogenic. Furthermore, antibiotic administration to treat intestinal infections during surgery or disease invariably kill off the normal flora and contribute to the proliferation and antibiotic resistance of virulent pathogenic strains. Thus, approaches focused on targeted delivery of therapeutic compounds to the intestinal epithelium that suppress pathogenic expression (i.e. virulence and tissue degrading activity) while allowing commensal bacteria to proliferate normally would be highly advantageous. Previous studies in the Alverdy laboratory at the University of Chicago have demonstrated that phosphate becomes depleted in the intestinal tract following surgical injury and is a major “cue” that triggers bacterial virulence. Furthermore, phosphate or polyphosphate supplementation has been shown to prevent in vitro bacterial transition to virulence and to prevent impaired intestinal healing (anastomotic leak) with oral polyphosphate administration in mouse models of surgical anastomosis with intestinal inoculation. In this thesis we propose the use of polyphosphate loaded nanoparticles (NP-PPi) as a drug delivery approach to attenuate the expression of pathogens identified to produce elevated levels of the tissue destroying enzyme collagenase, resulting in intestinal healing impairment. A previously developed inverse miniemulsion polymerization process used for the creation of phosphate loaded poly(ethylene) glycol nanoparticles is adapted for post-loading of polyphosphate into the particles. This results in the formation of polyphosphate loaded nanoparticles (NP-PPi) with high polyphosphate concentration and in its sustained release. In vitro studies demonstrated that NP-PPi were effective at attenuating collagenase production and biofilm formation, two key markers of bacterial virulence, for clinically relevant gram-negative pathogens. Ex vivo and in vivo studies demonstrate that NP-PPi remain mucoadhesive onto intestinal explants and to the intestinal epithelium when delivered in combination with an adhesive polyethylene glycol block copolymer, PEG 15-20. Furthermore, ex vivo studies indicate that NP-PPi are effective at suppressing bacteria colonization, suggesting their potential for attenuating tissue invasion of host pathogens in vivo.
M.S. in Biomedical Engineering, May 2018
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DEVELOPMENT OF A HYDROGEL NANOPARTICLE SYSTEM FOR SUSTAINED DELIVERY OF ANIGOGENIC FACTORS FOR THERAPEUTIC NEOVASCULARIZATION
Title
DEVELOPMENT OF A HYDROGEL NANOPARTICLE SYSTEM FOR SUSTAINED DELIVERY OF ANIGOGENIC FACTORS FOR THERAPEUTIC NEOVASCULARIZATION
Creator
Young, Daniel A
Date
2018, 2018-05
Description
Neovascularization requires controlled and sustained delivery of proangiogenic factors to stimulate reperfusion of ischemic tissues. Tissue...
Show moreNeovascularization requires controlled and sustained delivery of proangiogenic factors to stimulate reperfusion of ischemic tissues. Tissue engineering strategies for therapeutic neovascularization have used proangiogenic, recombinant growth factors to direct vessel development. Recently, peptides that mimic the bioactivity of growth factors have emerged as therapeutics for a variety of drug delivery applications, including therapeutic neovascularization. We designed hydrogel nanoparticles to provide sustained and tunable di usion-based release of a proangiogenic peptide, QK, and a vessel stabilizing peptide, Vasculotide (VT). These nanoparticles were combined with a tissue engineering sca old to promote tissue neovascularization. We used this nanocomposite system, utilizing peptide loaded hydrogel nanoparticles embedded in an implantable sca old, to investigate the e cacy of a dual peptide delivery strategy for therapeutic neovascularization. Inverse phase mini-emulsion polymerization (IPMP) was used to generate crosslinked poly(ethylene) glycol (PEG) hydrogel nanoparticles. We characterized the nanoparticles in terms of their swelling ratio, mesh size, surface charge ( -potential), and particle size distributions. We developed several nanoparticle formulations using various sizes and molar concentrations of PEG chains to study the e ects of crosslink density on peptide release kinetics. This resulted in the formation of nanoparticles with low and high crosslink density as well as time-dependent variations in network density due to hydrolysis. We utilized two di erent loading techniques, peptide entrapment during IPMP and peptide post-loading into the nanoparticles, and found both to be e ective via peptide loading measurements and release kinetic studies. In the case of entrapment loading, peptides were included in the aqueous precursor during nanoparticle IPMP. Peptide release kinetics were tuned through adjustments in nanoparticle crosslink density. The resulting nanoparticle crosslink density impacted both peptide loading and fractional release, as studies showed higher crosslink density nanoparticles resulted in slower peptide release. The IPMP process preserved QK secondary structure and bioactivity, as con rmed with released peptide using circular dichroism spectroscopy and a Matrigel tubulogenesis assay, respectively. In the case of the post-loading method, pristine nanoparticles were soaked in various concentrations of either QK or VT. Unlike with the entrapment loading method, crosslink density of the nanoparticles had little e ect on release kinetics. However, much higher mass amounts of peptide could be loaded using this method and thus this method was chosen for the in vivo studies. Next, we developed a hydrogel nanocomposite sca old system to sequester nanoparticles for implantation. We characterized the nanocomposite sca old system experimentally and theoretically using one-dimensional transport models of molecular di usion. We estimated peptide di usion coe cients from nanoparticles and the nanocomposites under perfect sink conditions. Importantly, we found this system capable of providing previously reported therapeutic thresholds of QK and VT. Finally, the in uence of sustained release of QK and VT on neovascularization was evaluated using a subcutaneous rat implant model. Results demonstrated statistically higher increases in perfused vessel density from peptide loaded nanocomposite sca olds as compared to sca olds where peptide was simply entrapped. These results suggest that controlled release of proangiogenic peptides from the developed nanoparticle system holds great potential for ischemic tissue repair.
Ph.D. in Biomedical Engineering, May 2018
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