Bacterial surface fouling is problematic for a wide range of applications and industries, including, but not limited to medical devices (implants, replacement joints, stents, pacemakers), municipal infrastructure (pipes, wastewater treatment), food production (food processing surfaces, processing equipment), and transportation (ship hulls, aircraft fuel tanks). One method to combat bacterial biofouling is to modify the topographical structure of the surface in question, thereby limiting the ability of individual cells to attach to the surface, colonize, and form biofilms. Multiple research groups have demonstrated that micro and nanoscale topographies significantly reduce bacterial biofouling, for both individual cells and bacterial biofilms. Antifouling strategies that utilize engineered topographical surface features with well-defined dimensions and shapes have demonstrated a greater degree of controllable inhibition over initial cell attachment, in comparison to undefined, texturized, or porous surfaces. This review article will explore the various approaches and techniques used by researches, including work from our own group, and the underlying physical properties of these highly structured, engineered micro/nanoscale topographies that significantly impact bacterial surface attachment.

It is well documented that bacterial adhesion to surfaces is mediated by the physical and chemical properties of the substrate, as well as the surface characteristics of the organism. Topographical features that limit cell-surface interactions have been shown to reduce surface colonization and biofilm formation. In this study, bacterial attachment to medically relevant materials was evaluated. Our data show that Escherichia coli attachment to glass, silicone, and titanium surfaces was most affected by the surface energy of these materials, as determined by water contact angle. The inherent roughness of the surface, however, was not correlated with cell attachment density. To study the effect of engineered surface roughness on bacterial attachment, topographical features, including arrays of holes and repeating lines/trenches, were formed from silicon wafers and then used as a template to imprint silicone-based polydimethylsiloxane (PDMS). Patterned silicone surfaces were then used in static and microfluidic flow-based experiments to evaluate cellular settlement and attachment. Cell attachment was observed to be strongly dependent upon the topographical features under both static and microfluidic flow conditions. The highest attachment density was observed on flat, un-patterned surfaces, while linear patterned surfaces showed greatly reduced cell attachment. Moreover, surfaces consisting of arrays of holes further reduced cell attachment as compared to linear patterns. These results demonstrate that the size, spacing, and shape of surface features play a significant role in cellsurface attachment and provide insight for the design of surfaces with antifouling properties.

Bacterial pathogens, such as Pseudomonas aeruginosa, readily form biofilms on surfaces, limiting the efficacy of antimicrobial and antibiotic treatments. To mitigate biofilm formation, surfaces are often treated with antimicrobial agents, which have limited lifetime and efficacy. Recent studies have shown that well-ordered topographic patterns can limit bacterial attachment to surfaces and limit biofilm formation. In this study, nano and microscale patterned poly(dimethylsiloxane) surfaces were evaluated for their ability to affect adhesion and biofilm formation by Pseudomonas aeruginosa. Feature size and spacing were varied from 500 nm to 2 μm and included repeating arrays of square pillars, holes, lines and biomimetc Sharklet™ patterns. Bacterial surface adhesion and biofilm formation was assessed in microfluidic flow devices and under static conditions. Attachment profiles under static and fluid flow varied within topography types, sizes and spacing. Pillar structures of all sizes yielded lower surface attachment than line-based patterns and arrays of holes. This trend was also observed for biomimetic Sharklet™ patterns, with reduced bacterial attachment to "raised" features as compared to "recessed" features. Notably, none of the topographically patterned surfaces outperformed smooth surfaces (without topography) for resisting cell adhesion. Initial surface attachment patterns were indicative of subsequent biofilm formation and coverage, suggesting a direct role of surface topography in biofilm-based biofouling.