Biofilms are sessile colonies of microbes attached to a variety of surfaces. Such ubiquitous structures cause serious problems such as persistent infections and biocorrosion. According to NIH, biofilms are involved in approximately 80% of human bacterial infections. We recently reported that self-assembled monolayers presenting tri(ethylene) glycol (TEG) are highly resistant to adhesion and biofilm formation of Escherichia coli. To further understand microbe-surface interactions and to develop effective biofilm control strategies, novel self-assembled monolayers (SAMs) of alkanethiols presenting mannitol group on gold films were analyzed for their resistance to biofilm formation in this study. The cell adhesion and biofilm formation were monitored with confocal laser scanning microscopy. The three dimensional structure of biofilms was analyzed with the COMSTAT software to quantify the biomass, surface coverage, and thickness. The mannitol-terminated SAM exhibited strong resistance not only to the biofilm formation of E. coli RP437 (84.1% ± 4.5% reduction), but also to that of the opportunistic human pathogens Pseudomonas aeruginosa PA01 (88.8% ± 9.0% reduction) and Candida albicans SC5314 (86.6% ± 9.0% reduction) compared to bare gold surface. This suggests that the bioinertness of mannitol-terminated SAMs is not species-specific because they are resistant to both bacterial and fungal biofilm formation. In addition, the long-term biofilm assay in a flow cell showed that mannitol-terminated SAMs were resistant to E. coli biofilm formation for at least 4 weeks, which is four times longer than TEG-terminated SAMs. To our best knowledge, mannitol-terminated SAM has the longest resistance to microbial biofilm formation compared to other SAMs reported to date. Such well-defined surfaces are an ideal platform for studying microbes-surface interactions and developing effective control strategies for antifouling and anticorrosion applications.

Keyword: self-assembled monolayers, biofilm, mannitol, tri-(ethylene glycol)