| Inflammatory bowel diseases, most notably Crohn's disease and ulcerative colitis, currently affect millions of patients worldwide and lead to prolonged inflammation of the digestive tract. Current treatment plans focus on systemic delivery of drugs; however these drugs frequently fail or are inadequate to prevent or reverse the damage. The purpose of this study is to develop a new class of colonoscope-based treatment options that specifically target the diseased area and locally deliver drugs and stem cells through sprayable application of a regenerative hydrogel during diagnostic procedures. Thermoresponsive hydrogel solutions can facilitate on-demand delivery of drugs and viable cell populations through instant solidification on intestinal tissue. Ultimately, the regeneration of diseased or damaged sections of the intestinal tract could maintain deep remission, increase intestinal function, reduce symptoms, and provide a higher quality of life for patients.;Towards this end, poly(N-isopropylacrylamide) (NiPAAm)-based thermogelling and crosslinking polyamidoamine (PAMAM) macromers were synthesized and combined to create a sprayable, in situ forming dual gelling hydrogel system for delivery of cellular hydrogel coatings onto warm tissues. Airbrush spraying was utilized as an operating tool to investigate the effects of solution formulation, pressure, and viscosity on the viability of fibroblast cells encapsulated in hydrogels. Smooth, fast, and conformal hydrogel coatings were obtained when thermogelling macromers were sprayed with high PAMAM concentration at low pressure. Cell viability was maximized when delivered by a dual-stream spraying method due to decreases in viscosity, pressure, and the effects of micronetwork formation in a turbulent stream. These results demonstrated that sprayable cell-loaded thermoresponsive hydrogel coatings offer promise as novel therapies for applications in intestinal tissue engineering.;Each year, many patients who suffer from Crohn's disease undergo resection of long segments of small intestine, and these procedures can leave patients with short-bowel syndrome. One solution to this clinical problem is transplanting biologically-compatible decellularized intestinal scaffolds with intact vasculature and preserved anatomic architecture. However, current cell seeding techniques for reconstitution of intestinal epithelium on the decellularized scaffold are not efficient. To this end, spray technology was investigated as a cell seeding technique for repopulation of decellularized small intestine. While organoids seeded through pipetting demonstrated aggregation, organoids spray-seeded at 0.35 bar formed an epithelial monolayer that mimicked the absorptive surface found on intestinal villi. The findings suggest that spraying holds great potential as a cell seeding technique for large-scale tubular organ recellularization.;Finally, the impact of macromer chemistry on the viability and activity of encapsulated cells was investigated. Pendant epoxide rings were introduced into a NiPAAm-based in situ forming hydrogel via copolymerization with glycidyl methacrylate. Incorporation of epoxide groups was found to improve biocompatibility of the hydrogels through chemical binding of serum proteins onto the polymer network structure, which led to increased cell attachment, proliferation, and cluster formation. These results demonstrated that free epoxide addition could be a powerful tool to alter cell behavior through controlling material chemistry with applications in tissue engineering and regenerative medicine. |
