Combinatorial materials research applied to the development of new surface coatings III. Utilisation of a high-throughput multiwell plate screening method to rapidly assess bacterial biofilm retention on antifouling surfaces.

The authors recently reported on the development of a novel multiwell plate screening method for the high-throughput assessment of bacterial biofilm retention on surfaces. Two series of biocide containing coatings were prepared to assess the ability of the developed assay to adequately discern differences in antifouling performance: i) a commercially available poly(methyl methacrylate) (PMMA) and silicone elastomer (DC) physically blended with an organic antifouling biocide Sea-Nine 211 (SN211) (4,5-dichloro-2-n-octyl-3(2H)-isothiazolone), and ii) a silanol-terminated polydimethylsiloxane (PDMS-OH) reacted with an alkoxy silane-modified polyethylenimine containing bound ammonium salt groups (PEI-AmCl). Three marine bacteria were utilised to evaluate the SN211 blended coatings (Pseudoalteromonas atlantica ATCC 19262, Cobetia marina ATCC 25374, Halomonas pacifica ATCC 27122) and the marine bacterium Cytophaga lytica was utilised to evaluate the PEI-AmCl/PDMS-OH coatings. The SN211 blended coatings showed a general trend of decreasing biofilm retention as the concentration of SN211 increased in both PMMA and DC. HPLC analysis revealed that reduction in biofilm retention was positively correlated with the amount of SN211 released into the growth medium over the length of the bacterial incubation. When compared to PMMA, DC consistently showed an equal or greater percent reduction in biofilm retention as the level of SN211 loading increased, although at lower loading concentrations. Evaluations of the PEI-AmCl/PDMS-OH coatings with C. lytica showed that all PEI-AmCl loading concentrations significantly reduced biofilm retention (p<0.0001) by a surface contact phenomenon. The high-throughput bacterial biofilm growth and retention assay has been shown to be useful as an effective primary screening tool for the rapid assessment of antifouling materials.