Synthesis of Biopolymer Materials Tailored for Biological Applications

Biopolymers are able to address a wide variety of medical concerns from chronic wounds to stem cell cultivation to antibacterial and antifouling applications. They are non-toxic, biodegradable, and biocompatible, making them ideal candidates for creating green materials for biological applications. In this thesis, we cover the synthesis of two novel materials from the biopolymers, chitosan and pectin. Chitosan is a biocompatible antibacterial polycation and pectin is an anti-inflammatory polyanion with a strong propensity for hydrogen-bonding. The two chitosan:pectin materials, particles and hydrogels, explore some of the structures that can be created by tuning the electrostatic interactions between chitosan and pectin. Chitosan can spontaneously form polyelectrolyte complexes when mixed with a polyanion in appropriate aqueous conditions. In the first study, chitosan:pectin nanoparticles were synthesized using an aqueous spontaneous ionic gelation method. A number of parameters, polymer concentration, addition order, mass ratio, and solution pH, were then explored and their effect on nanoparticle formation was determined. The synthesis of chitosan:pectin hydrogels have previously been limited by harsh acidic synthesis conditions, which restricted their use in biomedical applications. In the second study, a zero-acid hydrogel has been synthesized from a mixture of chitosan and pectin at biologically compatible conditions. We demonstrated that salt could be used to suppress long-range electrostatic interactions to generate a thermoreversible biopolymer hydrogel that has temperaturesensitive gelation. We then characterized the hydrogel system’s suitability for use as a wound dressing. iv An additional theme throughout this work includes using shear rheology as a powerful characterization tool to improve synthesized systems and collect important structural data for the creation of synthetic analogs. An electrospun emulsion system was tuned to maximize the amount of oil that could be spun into defect-free chitosan-based fibers. The Young’s modulus and complex viscosity of porcine bone marrow, porcine lung, porcine brain, and muscine brain were determined to enable the development of hydrogels that mimic these characteristics. We also explored the effects of using antifouling dopamine as a crosslinking agent for a poly(ethylene glycol) hydrogel system. Finally, with the goal of returning to green syntheses, we produced a simple selfassembling system for adding antibacterial activity to alkyd paints. Divalent metal naphthenates were used to catalyze oxidative crosslinking that form entrained metal nanoparticles as a byproduct. Overall, we have used a combination of rheology, knowledge of biopolymer interactions, and a desire to make syntheses cheaper and less hazardous to create an array of green biopolymer materials that are tailored for biological applications