Nanoporous anodic alumina reduces Staphylococcus biofilm formation

Abstract

Staphylococcus epidermidis and Staphylococcus aureus, two bacterial strains commonly associated with biofilm‐related medical infections and food poisoning, can rapidly colonize biotic and abiotic surfaces. The present study investigates the ability of anodic alumina surfaces with nanoporous surface topography to minimize the attachment and biofilm formation mediated by these pathogenic bacterial strains. Early attachment and subsequent biofilm development were retarded on surfaces with nanopores of 15–25 nm in diameter compared to surfaces with 50–100 nm pore diameter and nanosmooth surfaces. After 30 min of incubation in nutritive media, the biomass accumulation per unit surface area was 2·93 ± 1·72 µm3 µm‐2 for the 15 nm, 3·49 ± 1·97 µm3 µm‐2 for the 25 nm, as compared to 14·04 ± 6·39 µm3 µm‐2 for the nanosmooth, 11·88 ± 9·72 µm3 µm‐2 for the 50 nm and 12·09 ± 11·84 µm3 µm‐2 for the 100 nm surfaces respectively. These findings suggest that anodic alumina with small size nanoscale pores could reduce the incidence of staphylococcal biofilms and infections, and shows promise as a material for a variety of medical applications and food contact surfaces. Significance and Impact of the Study This paper reports on a simple, robust and scientifically sound method to reduce attachment and biofilm formation by Staphylococcus aureus and Staphylococcus epidermidis to abiotic surfaces using a carefully designed nanoscale topography. This approach can help to reduce the incidence of staphylococcal biofilms and infections without imposing selective stresses on bacteria, thus preventing the creation of resistant strains.

Orthogonal Nano-Engineering (ONE): Modulating Nanotopography and Surface Chemistry of Aluminum Oxide for Superior Antifouling and Enhanced Chemical Stability

“…The authors noted that the "hillocks" nanotopography (~50 nm in diameter) and surface hydrophobicity (akyl-terminated monolayer) each enhanced bacterial attachment and colonization, but quantification of the interactions was not reported. However, we observed that the smaller pore surfaces (AAO15 and AAO25), being rougher than NS, reduced biomass compared with the NS control, which is in good agreement with our previous reports 7,19,53 . This apparent contradiction in the biomass trends with regard to roughness once again underscores the necessity of characterizing the exact details of nanotopography beyond simple roughness measurements 54 .…”

“…We first focus on the effect of nanotopography alone on biofilm accumulation. Consistent with our previous studies 7,8,19 , bacterial presence on the uncoated small nanopores (AAO15 and AAO25) was substantially reduced compared with either the uncoated large pores (AAO100) or NS controls, for all bacteria. Both visual inspections and quantitative evaluations of biomass indicate that the extent and morphology of biomass also varied noticeably among the tested bacteria.…”

“…AAO has thermal and mechanical durability 17 that make it attractive for a wide range of engineering and scientific applications 18 . Studies have demonstrated that AAO substrates with nanoscale cylindrical pores of 15-25 nm diameters can effectively reduce bacterial attachment and biofilm formation, when compared with their 100-nm counterparts or a nanosmooth control 8,19 . Physicochemical and biological factors may both play important roles in bacterial responses to nanotopography 8,[20][21][22] .…”

Recent developments in antimicrobial and antifouling coatings to reduce or prevent contamination and cross‐contamination of food contact surfaces by bacteria

“…A similar hydration layer strategy was employed by Feng et al. (2019) without using polymers, where these researchers prepared textured alumina surfaces by anodization. The anodization process resulted in nanotextured alumina.…”

Toward Programming Bacterial Behavior via Synthetic Interfaces: Physicochemical Nanopatterning, Decoupling Surface Properties, and Integrating Material and Biological Insights

“…Studies in the past decade have demonstrated early promises for sublithographic patterning by electron beam lithography and directed self-assembly techniques (e.g., block copolymers, nanoparticles, and anodization). In addition to the nanoscale surface patterns, nanostructures fabricated using bulk materials, such as the nanopores in anodic aluminum oxide (AAO), offer a useful platform for studying bacteria–surface interactions. ,, Existing anodic etching protocols have produced hexagonally arranged nanopores (circular, triangular, or squarely shaped) with tunable aspect ratios (e.g., diameter, 6–500 nm; pore length, tens of nm to hundreds of μm) ,, distributed over macroscopic areas (on the order of cm 2 to m 2 ), without requiring a clean room. The chemical stability of aluminum oxide also provides a resilient foundation for subsequent engineering of surface chemistry and biofunctionality, for understanding decoupled effect of surface properties on bacterial behaviors, as discussed below.…”