Bacterial attachment and biofilm formation on surfaces are reduced by small-diameter nanoscale pores: how small is small enough?

Abstract

Background/Objectives:Prevention of biofilm formation by bacteria is of critical importance to areas that directly affect human health and life including medicine, dentistry, food processing and water treatment. This work showcases an effective and affordable solution for reducing attachment and biofilm formation by several pathogenic bacteria commonly associated with foodborne illnesses and medical infections.Methods:Our approach exploits anodisation to create alumina surfaces with cylindrical nanopores with diameters ranging from 15 to 100 nm, perpendicular to the surface. The anodic surfaces were evaluated for attachment by Escherichia coli, Listeria monocytogenes, Staphylococcus aureus and Staphylococcus epidermidis. Cell–surface interaction forces were calculated and related to attachment.Results:We found that anodic alumina surfaces with pore diameters of 15 and 25 nm were able to effectively minimise bacterial attachment or biofilm formation by all the microorganisms tested. Using a predictive physicochemical approach on the basis of the extended Derjaguin and Landau, Verwey and Overbeek (XDLVO) theory, we attributed the observed effects largely to the repulsive forces, primarily electrostatic and acid–base forces, which were greatly enhanced by the large surface area originating from the high density, small-diameter pores. We also demonstrate how this predictive approach could be used to optimise different elements of surface topography, particularly pore diameter and density, for further enhancing the observed bacteria-repelling effects.Conclusions:We demonstrate that anodic nanoporous surfaces can effectively reduce bacterial attachment. These findings are expected to have immediate, far-reaching implications and commercial applications, primarily in health care and the food industry.

Nanoporous anodic alumina reduces Staphylococcus biofilm formation

“…Considering the extreme difficulty of combatting staphylococcal biofilms in general, and S. epidermidis biofilms in particular, these findings are very encouraging. The trend in attachment and biofilm formation by these two staphylococcal strains was similar to our previous studies that tested other species including Escherichia coli , Listeria innocua and L. monocytogenes (Feng et al , ), which suggests that these anti‐fouling surfaces may be effective against both Gram‐positive and ‐negative species. However, additional work is required to include more medically and foodborne relevant species, including other staphylococcal species.…”

“…Some mechanisms by which the anodic alumina surfaces deter initial attachment include, but may not be limited to: nanopore‐induced changes in repulsive physicochemical forces (e.g. electrostatic and hydration forces) (Feng et al , ), chemical gradients and conditioning films (Lazzara et al ; Liu et al ), and bacterial mechanosensing (Rizzello et al . , ).…”

Nanotechnology to the rescue: using nano-enabled approaches in microbiological food safety and quality

“…[49] Among the most common antifouling materials are Carbon Nanotubes,[50] mesoporous and nanoporous silica,[51,52] and Alumina. [53,54] More recently biofouling surfaces based on proteins have also been created. [55] Feng et al utilized aluminum oxide anodization surfaces to mitigate microbial attachment and biofilm formation, with promising results.…”

Effect of Surface Charge and Hydrophobicity Modulation on the Antibacterial and Antibiofilm Potential of Magnetic Iron Nanoparticles

“…Combating biofilm may be done by surface coating with a material that repels the bacterial cells preventing their attachment [58] or more effectively by inclusion of an agent which prevents biofilm formation. In the latter, the biofilm formation is reduced even in flowing system in addition to preventing its attachment to surfaces.…”