Normally Oriented Adhesion versus Friction Forces in Bacterial Adhesion to Polymer‐Brush Functionalized Surfaces Under Fluid Flow

Abstract

Bacterial adhesion is problematic in many diverse applications. Coatings of hydrophilic polymer chains in a brush confi guration reduce bacterial adhesion by orders of magnitude, but not to zero. Here, the mechanism by which polymer-brush functionalized surfaces reduce bacterial adhesion from a fl owing carrier fl uid by relating bacterial adhesion with normally oriented adhesion and friction forces on polymer (PEG)-brush coatings of different softness is studied. Softer brush coatings deform more than rigid ones, which yields extensive bond-maturation and strong, normally oriented adhesion forces, accompanied by irreversible adhesion of bacteria. On rigid brushes, normally oriented adhesion forces remain small, allowing desorption and accordingly lower numbers of adhering bacteria result. Friction forces, generated by fl uid fl ow and normally oriented adhesion forces, are required to oppose fl uid shear forces and cause immobile adhesion. Summarizing, inclusion of friction forces and substratum softness provides a more complete mechanism of bacterial adhesion from fl owing carrier fl uids than available hitherto.

Liquid-Infused Silicone As a Biofouling-Free Medical Material

“…This increased speed at the boundary reduces the normal adhesion forces that allow pathogens to adhere to solid surfaces, thus inhibiting attachment behavior. 59 It is possible that the bacteria slide along the inner wall of the tubing with much lower resistance than experienced in unmodified PDMS. 60 On the other hand, 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 bacteria on the iPDMS surface could become encased in silicone oil (which itself might inhibit biofilm production by blocking signals between organisms 61 ) and removed through an emulsion when exposed to sufficiently high shear forces.…”

Robust Low Friction Antibiotic Coating of Urethral Catheters Using a Catechol-Functionalized Polymeric Hydrogel Film

“…The relative friction coefficient decreased in all the polymercoated substrates, which was calculated by dividing the modified substrate's coefficient by the bare substrate ( Figure 4C). Given that surface friction contributes to the adhesion of bacteria in fluidic conditions, which then leads to the development of biofilm that is resistant to antimicrobial treatment (Katsikogianni and , 2004;Swartjes et al, 2014), the catechol-functionalized hydrogel coatings with significant reductions in the friction coefficients may offer a preventive strategy against the initial biofilm formation and its progression, in addition to providing lubricity to catheter surface.…”

“…Elastomers are commonly used materials for urethral catheters, such as latex rubber, silicone, polyvinyl chloride (PVC), and polyurethane (PU), given their excellent conformability and mechanical strength to form a robust channel for drainage (Dellimore et al, 2013). However, in general, the surface of elastomers has high lateral friction coefficient, causing the adhesion of urine components and external bacteria such as Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus), which is a pivotal step in their colonization and further biofilm formation (Swartjes et al, 2014;An et al, 2017). Furthermore, in the presence of urease-producing bacteria forming salt crystals on the surface, the catheter can be easily roughened to further increase friction, if not treated timely, causing massive obstruction (i.e., encrustation), antibiotic resistance of bacteria, and severe bacterial infection (Wang et al, 2015).…”

Implications for directionality of nanoscale forces in bacterial attachment

“…However, the amount of work ( W ) to overcome adhesion is a function of the pull-off angle θ , i.e., W = F · d ·cos( θ ), which indicates that the force required for detachment might change for different pull-off angles. Additionally, bacteria in most situations adhere from a flowing condition, in which the angle of approach leads to friction between a bacterium and the surface (Swartjes et al 2014b ). In fact, there is a relationship between adhesion and friction at nanoscale often used to describe the contact between two solid bodies, F f = µ ( F n + F adh ), stating that the friction force F f , equals the coefficient of friction ( µ ) multiplied by the sum of the normal force F n and the adhesion force F adh (Gao et al 2004 ).…”

“…A distinction can be made between two types of lateral forces; first, the shear adhesion force depending on the strength of the bond between an adhered bacterium and a surface, which breaks by moving the bacterium along the surface after it has adhered, and second, the lateral force arising between a bacterium and a surface when initial contact is made by a bacterium approaching the surface at an angle, representing the friction (Swartjes et al 2014b ). By challenging the shear strength of the adhesion bond using different flow rates of the liquid carrying the bacteria (Gazzola et al 2015 ), or by detachment induced by passage of a liquid-air interface (Perera-Costa et al 2014 ), estimations of the first type of lateral force have been made.…”