Saunders, Jacob – Synthesis and Characterization of Starch Nanoparticle Hydrogels (Dr. Todd Hoare)

Hydrophilic polymer gels (hydrogels) have extremely useful properties with respect to chemical and biomedical engineering. Nanoparticle hydrogels, in which nanoscale particles function as building blocks, can offer increased functional diversity and controllable release kinetics. Starch nanoparticles are hypothesized to be advantageous building blocks for biomedical hydrogels due to their cytocompatibility and functionalizability. Starch nanoparticles were functionalized with aldehyde and hydrazide groups to enable cross-linking through hydrazone chemistry, which can be performed rapidly under physiological conditions to facilitate in situ gelation following injection. Aldehyde functionalization was achieved utilizing sodium periodate to break the carbon-carbon bond between the adjacent hydroxyl groups via oxidation. Hydrazide functionalization was achieved by taking the aldehyde-functionalized nanoparticles and reacting them with a large excess of adipic acid dihydrazide followed by reductive amination. Four degrees of substitution (D.S.) were synthesized (0.05, 0.10, 0.25, 0.40) and analyzed with proton nuclear magnetic resonance spectroscopy to determine that the correct structures were attained. The gels were synthesized at five different concentrations (5, 7.5, 10, 25, and 35 wt%). Gelation times were measured directly using rheometry, providing information on their mechanical properties in the form of storage and loss moduli. The 0.25 D.S. appears to be the most promising with a gelation time of 114 seconds whereas the other degrees experienced difficulty in either gelation or dissolution in water. With the successful gelation of a pure SNP hydrogel, continued investigation of the gel properties such as mechanical strength, may open an exciting new realm of possibilities for biodegradable, optimizable drug delivery systems.