A high-throughput method for testing biofouling and cleaning of polymer hydrogel materials used in medical devices†
A miniaturized, high-throughput method is developed to measure biofouling and cleaning processes of transparent silicone- and hydroxyethylmethacrylate-based polymer hydrogel materials used in medical devices. Protein biofouling and cleaning effectiveness were measured in 384-well microtiter plates using 3 mm biopsy punches from hydrogel materials soaked in a simulated protein soil fluid (PSF). Fluorescence detection of labeled protein components enabled highly sensitive quantification of biofouling and cleaning endpoints. The sample volume to soaking volume ratio and surface area to soaking volume ratio are similar to those used for full-sized analysis. The method showed minimal perturbation from sample height variations up to hundreds of micrometers. A calibration curve constructed by testing samples soaked in eight different concentrations (0–1.25 mg mL−1) of fluorescent protein showed a broad dynamic range, but fluorescence quenching occurred above 0.75 mg mL−1 protein in highly absorbing hydrogels. The method was found to have 1 : 1 linear correlation with measurements obtained by 2D fluorescence imaging using biofouled/cleaned miniature punches, and 3D confocal fluorescence profiling using full-sized samples soaked in PSF. A comparison of protein biofouling on two types of hydrogel materials revealed that the slope of protein concentration–response curves for high water materials was 100-fold higher than for low water materials. To demonstrate simultaneous measurement of biofouling by multiple soil components, lipid and protein sorption were also tested and found to be correlated. The characterization and results obtained here show the potential of this method for exploring mechanistic details of biofouling and cleaning processes. The method greatly decreases the time and cost associated with the large number of unique samples required, making it possible to study the roles of the numerous material, solution and soil variables at the biointerface of medical devices.