Advanced in situ hydrogel assembly for guiding molecular release
Since the emergence of hydrogels as carriers for cells, bioactive molecules, and even metallic nanoparticles, there were extensive efforts to control the rate and direction of embedded molecular release, largely by additional chemical modification of gel-forming polymers. However, these approaches often encountered several challenges including the instability of molecular cargos, the extensive labor of synthesis and purification, and the uncontrollability of the molecular release direction. In contrast, many biological systems use their geometry to guide the release of their molecules or signals. Inspired by nature, this study presents unique approaches with advanced in situ formation techniques, which can overcome the problems and control the release direction and rate of the diverse embedded materials in a hydrogel. First, I demonstrated a self-folding, multi-walled poly(ethylene glycol) diacrylate (PEGDA) hydrogel tube. This tubular structure was obtained by in situ self-folding of a bi-layered PEGDA hydrogel patch constructed with gels of significantly different rigidity and expansion ratio. The radiuses of the resulting gel tubes were estimated with bilayer curvature equations and agreed with experimental data. Second, the resulting hydrogel was used to control the release rate and direction of embedded molecules by localizing the molecules in a center of the tube. A finite element method (FEM) based simulation was performed to explain the geometrical effect on controlling the molecular release. Additionally, the bilayered PEGDA hydrogel encapsulating VEGF was implanted on a chicken chorioallantoic membrane (CAM) to evaluate the neovascularization. Due to the spatiotemporal release of VEGF, the gel tubes significantly increased the density and diameters of blood vessels, compared to unfolded hydrogel patches and other ring-shaped hydrogels. Third, I presented a bio patch delivery system with minimal invasive manner by using the self-folding and unfolding technique. I assembled the hydrogel patch with a sacrificial layer that can dissolve in media after a controlled time. This hydrogel patch self-folded into a compact tube shape and delivered via a catheter to a targeted area followed by unfolding to a patch after a particular time. Lastly, I reported an in situ synthesis of metal nanoparticle-hydrogel composite that can sustainably reduce the release rate of embedded metal nanoparticles. The resulting gel composite with antimicrobial property of embedded metallic nanoparticles could control bacterial cell growth in an aqueous media and also inhibit biofilm formation on a polymeric and metallic substrates coated with the gel composite. Overall, this study was conducted for enhancing the efficacy of molecular compounds used for various agricultural products, food additives, sensor devices, and clinical treatments.
Hydrogels, Self-folding, Poly(ethylene glycol) diacrylate, Spatiotemporal release, Bio-patch delivery
University of Illinois - Urbana-Champaign
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University of Illinois at Urbana-Champaign