Abstract
The main focus of this work was to establish a correlation between surface topography and chemistry and surface colonization by lactic acid bacteria. For this reason, we chose gold substrates with different surface architectures (i.e., smooth and nanorough) that were characterized by atomic force microscopy (AFM), electron scanning microscopy (SEM), and X-ray diffractometry (XRD). Moreover, to enhance biocompatibility, we modified gold substrates with polymeric monolayers, namely cationic dextran derivatives with different molar masses. The presence of those layers was confirmed by AFM, infrared spectroscopy (IR), and X-ray photoelectron spectroscopy (XPS). In order to determine the adhesion abilities of non-modified and modified gold surfaces, we tested three lactic acid bacteria (LAB) strains (i.e., Lactobacillus rhamnosus GG, Lactobacillus acidophilus, and Lactobacillus plantarum 299v). We have shown that surface roughness influences the surface colonization of bacteria, and the most significant impact on the growth was observed for the Lactobacillus rhamnosus GG strain. What is more, covering the gold surface with a molecular polymeric film by using the layer-by-layer (LbL) method allows additional changes in the bacterial growth, independently on the used strain. The well-being of the bacteria cells on tested surfaces was confirmed by using selective staining and fluorescence microscopy. Finally, we have determined the bacterial metabolic activity by measuring the amount of produced lactic acid regarding the growth conditions. The obtained results proved that the adhesion of bacteria to the metallic surface depends on the chemistry and topography of the surface, as well as the specific bacteria strain.
Highlights
Since antiquity, some metals were considered suitable for producing self-sanitize items thanks to the oligodynamic effect [1]
As mentioned in the introduction section, it is well known that both surface topography and its chemistry play an important role in the adhesion process of microorganisms
Two gold substrates with different surface roughness were selected for experiments, i.e., the commercially available gold layer on glass (Au200) and the electrochemically synthesized gold layer on the copper substrate (Au(E))
Summary
Some metals were considered suitable for producing self-sanitize items thanks to the oligodynamic effect [1]. It is known that this bacteriostatic effect is induced by the surface properties of precious metals and the large specific surface area of nanostructures [2]. When it comes to the utility of metallic items and its biocidal features, the propagation of microorganisms on its surface is almost impossible, mainly due to the contact killing [3,4]. Bacteria adhesion to metallic surfaces is generally an unwanted phenomenon because of the vast demand for antibacterial materials [6,7,8,9], for some applications, e.g., in bioelectrochemical systems (BESs), the use of metal-based electrodes along with microorganisms grown on their surfaces is crucial [10]
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