Control of bacterial biofilm growth on surfaces by nanostructural mechanics and geometry

Abstract

As the dominant mode of bacterial existence, slimy surface-associated biofilms pervade natural and anthropogenic environments. Mature biofilms can be highly resistant to liquid or vapor antimicrobial attack and therefore pose persistent pathogenic threats. Surface chemistry treatments to inhibit biofilm growth have been found to only transiently affect initial attachment. In this work, we investigate the tunable effects of physical surface properties, including high-aspect-ratio (HAR) surface nanostructure arrays recently reported to induce long-range spontaneous spatial patterning of bacteria on the surface. The functional parameters and length scale regimes that control such artificial patterning for the rod-shaped pathogenic species Pseudomonas aeruginosa are elucidated through a combinatorial approach. We further report a crossover regime of biofilm growth on a HAR nanostructured surface versus the nanostructure effective stiffness. When the "softness" of the hair-like nanoarray is increased beyond a threshold, biofilm growth is inhibited as compared to a flat control surface. This is consistent with the mechanoselective adhesion of bacteria, a recently proposed mechanism previously considered unique to eukaryotic cells. Therefore by combining nanoarray-induced bacterial patterning and modulating the effective stiffness of the nanoarray-thus mimicking an extremely compliant flat surface-bacterial mechanoselective adhesion can be exploited to control and inhibit biofilm growth.

Nano and Microscale Topographies for the Prevention of Bacterial Surface Fouling

“…Bacterial attachment at this initial stage is, by all means, a complex process that is governed by multiple cell-surface interactions. These interactions can be greatly influenced by surface chemistry (functional groups, electrostatic charge, coatings), surface energy (as related to the surface hydrophobicity), mechanical properties (elastic modulus, shear forces), environmental conditions (pH, temperature, nutrient levels, competing organisms), surface topography, as well as bacterial surface structures (pili, flagella, fimbriae, adhesins) [7][8][9][10][11][12][13][14][15][16][17][18]. Cell attachment to surfaces is governed by a combination of all these factors (surface properties, environmental conditions, and cell physiology), making it virtually impossible to uncouple the influence of individual factors.…”

“…It is essential to note that most of these aforementioned studies focus on nano-roughened, nano-texturized, or nanoporous surfaces. Relatively few studies have addressed engineered nanoscale topography (containing well-defined features) [7,9].…”

“…This was done through the use of a high aspect ratio (HAR) pillared nanostructure array [9]. Their orthogonal double-gradient fabricated array consisted of a pitch gradient ranging from 0.8 to 4.0 μm, and an orthogonal nanopost diameter gradient from 300 nm to ~1 μm.…”

“…These HAR nano and microscale structures were shown to induce long-range spontaneous spatial patterning of P. aeruginosa cells while on the surface. This group has additionally found that substrate stiffness plays a role in bacterial attachment and biofilm formation [9]. They have determined that when the stiffness of their pillar-based nanostructures is reduced beyond a threshold value (i.e., when the surfaces become softer), biofilm formation becomes drastically reduced.…”

Electrical methods of controlling bacterial adhesion and biofilm on device surfaces

“…A new approach by researchers at Harvard University considers mechanical properties of the surface polymer and nanoscale surface properties to deter bacterial adherence [112]. Nanoposts on the surface of the polymer can attract or repel bacteria depending on the species of bacteria and the size, shape, and spacing of the nanoposts.…”