(M1130-09-61) Biofouling Assessment of Zwitterionised Superhydrophilic Polyvinyl Alcohol Hydrogels using E. coli and S. aureus

Purpose: To assess the biofouling inhibition potential of zwitterionised super hydrophilic Polyvinyl alcohol hydrogels using E. coli and S. aureus.

Methods: Zwitterionisation was modulated at 3 concentration levels, 0 %, 20%, and 33% with a zwitterionic polymer, SBMA. Protein adsorption onto the hydrogel, as an initial index for fouling, was evaluated in vitro from a complex protein solution constituted in artificial tear fluid and ex vivo using aqueous and vitreous humor extracted from a New Zealand albino rabbit's eyes. The total protein adsorbed onto the hydrogels was quantitatively determined using the BCA micro assay kit. The fouling potential was evaluated using 2 microorganisms namely, E. coli and S. aureus. In all experiments, the effect of the zwitterionising agent was evaluated at 3 concentration levels. Results were reported as the mean ± standard deviation of triplicate readings. When necessary, comparisons were made using the student's t-test and one-way ANOVA.

Results: The highest amount of protein (0.1036 ± 0.4224 µg/mm²) was adsorbed in vitro by the non-zwitterionic hydrogel as shown in Figure 1. There was a gradual decrease in the level of adsorbed protein as the concentration of SBMA in the hydrogel increased. Statistical analysis showed that the addition of SBMA contributed significantly to protein resistance in vitro with a p-value of 0.000531. The hydrogel with the highest level of SBMA had the least adsorbed protein (0.0487 ± 0.263 µg/mm²). Figure 2 shows that the hydrogel containing the highest level of zwitterionic SBMA was at least 50 % less susceptible to biofilm adhesion when compared to the pure unzwitterionised hydrogel sample, at all the time points and across the 2 microbes used for the assessment. In addition, the reduction in bacteria colonies on the hydrogel with the most zwitterionic content, between the 1-hour time point and 24-hour time point was over 87 % when compared to the non-zwitterionic hydrogel. Moreover, the standard deviation for all measurements involving the hydrogel with the highest zwitterionic polymer was very low especially when compared to the non-zwitterionic hydrogel. A similar trend was seen in the S. aureus medium. The number of colony-forming units (CFU) initially increased before going down. With a p-value of 0.011 and an F-value of 10.31, the SBMA content of the hydrogels significantly affected the number of bacteria adhering to the gels.

Conclusion: From the foregoing, the novel zwitterionised hydrogel has shown the potential to limit biofouling by the 2 microbes tested. The biofouling limiting potential was dependent on the content of the zwitterionic agent.

Acknowledgements: 1. Wits Advanced Drug Delivery Platform, Department of Pharmacy and Pharmacology, School of Therapeutic Sciences,, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
2. National Research Foundation

Figure 2. Biofilm adhesion analysis using E. coli and S. aureus

Figure 1. Ex vivo protein adsorption using aqueous and vitreous humor