TARGETED AND SUSTAINED DELIVERY OF POLYPHOSPHATE FOR SUPPRESSION OF BACTERIAL COLLAGENASE AND POST-SURGICAL INTESTINAL HEALING

Nanoparticle 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 201