Combinatorial materials research applied to the development of new surface coatings IV. A high-throughput bacterial biofilm retention and retraction assay for screening fouling-release performance of coatings

Abstract

A high-throughput bacterial biofilm retention screening method has been augmented to facilitate the rapid analysis and down-selection of fouling-release coatings for identification of promising candidates. Coatings were cast in modified 24-well tissue culture plates and inoculated with the marine bacterium Cytophaga lytica for attachment and biofilm growth. Biofilms retained after rinsing with deionised water were dried at ambient laboratory conditions. During the drying process, retained biofilms retracted through a surface de-wetting phenomenon on the hydrophobic silicone surfaces. The retracted biofilms were stained with crystal violet, imaged, and analysed for percentage coverage. Two sets of experimental fouling-release coatings were analysed with the high-throughput biofilm retention and retraction assay (HTBRRA). The first set consisted of a series of model polysiloxane coatings that were systematically varied with respect to ratios of low and high MW silanol-terminated PDMS, level of cross-linker, and amount of silicone oil. The second set consisted of cross-linked PDMS-polyurethane coatings varied with respect to the MW of the PDMS and end group functionality. For the model polysiloxane coatings, HTBRRA results were compared to data obtained from field immersion testing at the Indian River Lagoon at the Florida Institute of Technology. The percentage coverage calculations of retracted biofilms correlated well to barnacle adhesion strength in the field (R(2)=0.82) and accurately identified the best and poorest performing coating compositions. For the cross-linked PDMS-polyurethane coatings, the HTBRRA results were compared to combinatorial pseudobarnacle pull-off adhesion data and good agreement in performance was observed. Details of the developed assay and its implications in the rapid discovery of new fouling-release coatings are discussed.

New Directions in Antifouling Technology

“…Using a systematic, combinatorial and high-throughput approach [110], the effect of key compositional variables such as siloxane composition and polyol composition on the surface and bulk properties of the coating are being explored [111][112][113][114]. Rapid laboratory bioassays have also been developed to permit the screening of large numbers of coating samples in an efficient time frame [115,116]. Using this approach, coating compositions have been identified that have a combination of excellent release properties, stability in water, good adhesion and high bulk modulus, and are candidates for field testing.…”

Combinatorial and High‐Throughput Methods in Macromolecular Materials Research and Development

“…For some coatings it has been found that marine bacteria may retract from the surface of the coating and this has been correlated to the release performance of marine organisms from the coating surface. [144,149,150] These highthroughput methods have been used to screen a number of different candidate polymer and coatings compositions for their performance in the marine environment. [151][152][153][154][155][156] In addition, this workflow has also been used to study the structure-property relationships of UV-cured coatings [157] and for the exploration of hybrid organic-inorganic coatings.…”

Bacterial assay for the rapid assessment of antifouling and fouling release properties of coatings and materials

“…For example, the automated water jet apparatus was developed for screening of a range of potential foulingrelease coatings that were deposited in multiwell plates [17,34,35,37,39]. A water channel apparatus with fully calibrated turbulent flow was also used to quantify the fouling-release potential of coatings [32,36].…”