(695d) Enhancing Oxygen Permeability in Hydrogel Wound Dressing By Cyanobacterial Gas Vesicles

Hydrogel wound dressing is commonly used nowadays. However, for some wounds the use of hydrogel wound dressing may incur insufficient oxygen availability for proper healing. Oxygen has an important role in angiogenesis, cell motility, and extracellular matrix formation. Oxygen limitation during the wound-healing process is one of the major causes that can lead to formation of chronic wounds. Cyanobacterial gas vesicles are hollow, protein-walled, gas-filled structures in cylindrical shapes with conical caps. Gas vesicle wall is impermeable to liquid water but permeable to gases with very low mass transfer resistance. Because oxygen diffusivity in a gas phase is much higher than that in liquid and solid phases, introducing gas vesicles into the hydrogel has the possibility of effectively enhancing oxygen permeation through the gel. Nonetheless, we have shown earlier that if dispersed randomly, gas vesicles need to be provided in high volume fractions to be effective in enhancing oxygen transfer, because the oxygen transferring rapidly through the gas vesicles is bottlenecked by the slow transfer across the liquid/gel continuous phase that separates the dispersed vesicles. We have thus taken the approach of attaching gas vesicles as continuous layers on the surface of fibers that extend across the whole hydrogel thickness. For example, PMMA coated, highly porous, and large pored polyurethane foam can be introduced as a core porous structure in the hydrogel wound dressing. After the coated PMMA surface is gently modified by acid hydrolysis, gas vesicles collected from the Anabaena flos-aqua culture are chemically attached onto the modified surface. This foam structure creates connected gas vesicle layers or channels that allow fast oxygen transfer through the hydrogel wound dressing. The PMMA surface modification has been optimized and tested. AFM pictures confirmed the attachment of gas vesicles on the modified surface. Much faster oxygen permeation through attached gas vesicle layers has been visualized by the localized color change in resazurin solution immediately adjacent to the gas vesicle-attached surface of a PMMA strip placed in the originally colorless anaerobic solution. We are currently measuring the oxygen permeability to provide more quantitative information on the oxygen transfer enhancement offered by different methods and amounts of gas vesicle attachment on surfaces. Results of cyanobacterial gas vesicle production and harvesting as well as the oxygen transfer enhancement achieved through the use of gas vesicle will be reported and discussed in the presentation.