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.
Highlights
Biofilms are the prevailing lifestyle of bacteria in most natural environments
This study clearly shows that the small nanoscale pore anodic alumina surfaces can effectively limit cell attachment and biofilm formation by a range of bacteria relevant for medical, biomedical and food processing applications
Bacterial attachment to abiotic surfaces and subsequent biofilm formation are complex processes, controlled by the interplay between biological factors, such as secretion of extracellular materials by the bacteria,[29] bacterial appendages and other cell surface structures that can contribute to bacterial sensing of the surface,[9] and physicochemical factors, such as surface topography, surface charge and surface energy.[14]
Summary
Biofilms are the prevailing lifestyle of bacteria in most natural environments. They consist of microbial communities that usually accumulate at solid–liquid interfaces and are entrapped in a matrix of highly hydrated extracellular polymeric substances.[1]. United States Centers for Disease Control and Prevention estimates that about 2,500 listeriosis and 500 associated deaths occur yearly.[16] The ubiquitous L. monocytogenes can be transmitted through raw foods, the environment, utensils or processing equipment.[17,18,19] Infection with E. coli O157:H7 can lead to severe foodborne illness, haemorrhagic diarrhoea and haemolytic uraemic syndrome.[16,20,21] Contamination with S. aureus is the root cause for a range of illnesses, from food poisoning to infections of the skin and soft tissue, to respiratory, bone, joint and endovascular disorders; S. aureus is the most frequently isolated pathogen from wound infections.[22,23] S. epidermidis has been. Visualisation of biomass structures was conducted with a Zeiss LEO 1550 field emission scanning electron microscopy, and images acquired with the SmartSEM software (Carl Zeiss Microscopy, LLC, Hamburg, Germany)
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