Influence of Cross-Linker Chemistry on Polyampholyte Hydrogel Long Duration Resistance to <i>Ralstonia pickettii</i> Adhesion

Industrial systems transporting water for potable and nonpotable uses are extremely susceptible to biofilm formation and subsequent biofouling. Biofilm formation has significant impacts on these systems, including mechanical failures, reduced product quality, and human health. Polyampholyte hydrogels composed of [2-(acryloyloxy)ethyl] trimethylammonium chloride (TMA) and 2-carboxyethyl acrylate (CAA) have been previously shown to exhibit bacterial resistant properties over short durations. This study investigates the ability of TMA/CAA hydrogels to resist bacterial adhesion over long durations of up to 28 days. TMA/CAA hydrogels were synthesized with one of three cross-linker species: diethylene glycol dimethacrylate (DEGDMA), carboxybetaine dimethacrylate (CBMAX), or [N-(2-ammonio-3-(methacryloyloxy)propanoyl)-O-methacryloylserinate (Ser-Ser) to evaluate the influence of cross-linker chemistry. Swelling, percent hydration, shore hardness, and degradation studies were completed as assessments of the physical properties. Ralstonia pickettii surface coverage was analyzed by confocal microscopy at time points ranging from 1 day to 4 weeks. The results demonstrate that TMA/CAA hydrogels cross-linked with zwitterionic species outperform those cross-linked by DEGDMA, even at early time points. The hydrogels cross-linked with Ser-Ser and CBMAX perform identically until they have been repeatedly exposed to bacteria for 4 weeks. At that time, bacterial adhesion to CBMAX cross-linked hydrogels became statistically greater than that to Ser-Ser cross-linked hydrogels, although both maintain less than 0.03% surface coverage. These results suggest that TMA/CAA hydrogels cross-linked with Ser-Ser have great potential for reducing or eliminating bacterial adhesion in long duration applications.