A novel biofilm channel for evaluating the adhesion of diatoms to non-biocidal coatings

Abstract

Laboratory assessment of the adhesion of diatoms to non-toxic fouling-release coatings has tended to focus on single cells rather than the more complex state of a biofilm. A novel culture system based on open channel flow with adjustable bed shear stress values (0–2.4 Pa) has been used to produce biofilms of Navicula incerta. Biofilm development on glass and polydimethylsiloxane elastomer (PDMSe) showed a biphasic relationship with bed shear stress, which was characterised by regions of biofilm stability and instability reflecting cohesion between cells relative to the adhesion to the substratum. On glass, a critical shear stress of 1.3–1.4 Pa prevented biofilm development, whereas on PDMS, biofilms continued to grow at 2.4 Pa. Studies of diatom biofilms cultured on zwitterionic coatings using a bed shear stress of 0.54 Pa showed lower biomass production and adhesion strength on poly(sulfobetaine methacrylate) compared to poly(carboxybetaine methacrylate). The dynamic biofilm approach provides additional information to supplement short duration laboratory evaluations.

Keywords:

• diatom biofilms
• adhesion
• fouling-release
• zwitterionic coatings
• polydimethylsiloxane
• Navicula incerta

Acknowledgements

This research was supported by the Office of Naval Research grant N00014-08-1-0010. The PDMSe surfaces (glass slides coated with Silastic^®-T2) were provided by Professor A.B. Brennan of the University of Florida. SBMA and CBMA zwitterionic films were supplied by Professor S. Jiang of the University of Washington.