Microscale Correlation between Surface Chemistry, Texture, and the Adhesive Strength ofStaphylococcusepidermidis

Abstract

Staphylococcus epidermidis is among the most commonly isolated microbes from medical implant infections, particularly in the colonization of blood-contacting devices. We explored the relationships between surface wettability and root-mean-square roughness (Rq) on microbial adhesive strength to a substrate. Molecular-level interactions between S. epidermidis and a variety of chemically and texturally distinct model substrata were characterized using a cellular probe and atomic force microscopy (AFM). Substrata included gold, aliphatic and aromatic self-assembled monolayers, and polymeric and proteinaceous materials. Substrate hydrophobicity, described in terms of the water contact angle, was an insufficient parameter to explain the adhesive force of the bacterium for any of the surfaces. Correlations between adhesion forces and Rq showed weak relationships for most surfaces. We used an alternate methodology to characterize the texture of the surface that is based on a fractal tiling algorithm applied to images of each surface. The relative area as a function of the scale of observation was calculated. The discrete bonding model (DBM) was applied, which describes the area available for bonding interactions over the full range of observational scales contained in the measured substrate texture. Weak negative correlations were obtained between the adhesion forces and the area available for interaction, suggesting that increased roughness decreases bacterial adhesion when nano- to micrometer scales are considered. We suggest that modification of the DBM is needed in order to include discontinuous bonding. The adhesive strength is still related to the area available for bonding on a particular scale, but on some very fine scales, the bacteria may not be able to conform to the valleys or pits of the substrate. Therefore, the bonding between the bacterium and substrate becomes discontinuous, occurring only on the tops of ridges or asperities.

Fabrication of a platform to isolate the influences of surface nanotopography from chemistry on bacterial attachment and growth

“…Conversely, other authors have reported that that an increase in the nanoscale roughness of the substrate surface leads to a decrease in the extent of bacterial attachment, 12,[17][18][19] and even a decrease in bacterial adhesion when nano-to micrometer scales are considered. 20 These apparently conflicting and contradicting studies highlight the need for the development of a platform that can produce homogeneous nanotopography that does not alter the chemistry of the surface.…”

Rapid and Serial Quantification of Adhesion Forces of Yeast and Mammalian Cells

“…Force spectroscopy approaches using atomic force microscopy (AFM) [9] have provided novel information on cell adhesion, particularly at the single-molecular level, and on the nanomechanical properties of cells [10]. Single-cell force spectroscopy (SCFS) of eukaryotic [11]–[13] and prokaryotic [14], [15] cells, which are attached to the end of a tipless AFM cantilever, allows the quantification of the adhesion force of the entire cell to a given substrate and makes possible the study of the contribution of distinct molecular classes to the overall adhesion event [10]. This force quantification helps unravel the adhesion-related gene products, mechanisms and regulatory signals [16].…”

Atomic Force Microscopy of Biofilms—Imaging, Interactions, and Mechanics

“…The author then moved this on to look at the adhesion of fungal and bacterial spores [77,78]. Protocols for the construction of cell probes have varied in the method of cantilevers functionalization: electrostatic compounds; poly(ethyleneimine) (PEI), poly-L-lysine, or hydrophobic substances, and the use of glue, chemical fixation, and bio-inspired wet adhesives have all been used, and in the type of probe that was created: single versus multicellular [3,[79][80][81][82][83][84][85]. While all methods succeeded in the creation of a cellular functionalized tip and the acquisition of adhesive force-curve data, the results and validity of the techniques varied.…”