Inhibition of Wild Enterobacter cloacae Biofilm Formation by Nanostructured Graphene- and Hexagonal Boron Nitride-Coated Surfaces

Abstract

Although biofilm formation is a very effective mechanism to sustain bacterial life, it is detrimental in medical and industrial sectors. Current strategies to control biofilm proliferation are typically based on biocides, which exhibit a negative environmental impact. In the search for environmentally friendly solutions, nanotechnology opens the possibility to control the interaction between biological systems and colonized surfaces by introducing nanostructured coatings that have the potential to affect bacterial adhesion by modifying surface properties at the same scale. In this work, we present a study on the performance of graphene and hexagonal boron nitride coatings (h-BN) to reduce biofilm formation. In contraposition to planktonic state, we focused on evaluating the efficiency of graphene and h-BN at the irreversible stage of biofilm formation, where most of the biocide solutions have a poor performance. A wild Enterobacter cloacae strain was isolated, from fouling found in a natural environment, and used in these experiments. According to our results, graphene and h-BN coatings modify surface energy and electrostatic interactions with biological systems. This nanoscale modification determines a significant reduction in biofilm formation at its irreversible stage. No bactericidal effects were found, suggesting both coatings offer a biocompatible solution for biofilm and fouling control in a wide range of applications.

Interactions Between 2D Materials and Living Matter: A Review on Graphene and Hexagonal Boron Nitride Coatings

“…However, these approaches are non-specific, which leads to environmental impact resulting from their effect on species not involved in biofilm formation ( Parra et al, 2015a ). While typical approaches rely on the application of coatings with bactericidal payloads, these present limitations such as low durability and gradually lead to bacterial resistance development as well as negative environmental impacts ( Reed et al, 2019 ; Zurob et al, 2019 ). Other control strategies imply the use of polymeric coatings, such as epoxy.…”

“… Parra et al (2015c , 2017) have shown that this mechanism is effective in controlling MIC in Cu and Ni substrates. Zurob et al (2019) studied the effect of graphene and hBN coatings on a wild Gram- Enterobacter cloacae strain biofilm. Graphene-coated glass exhibits 83.6% less biofilm than uncoated glass.…”

“…While both coatings contribute to a significant reduction of the biofilm, no bactericidal effects were found, suggesting that the bactericidal effect is independent of the charge transfer capabilities of the substrate, and that biofilm reduction could be attributed to decreased cellular adhesion. The authors mention the influence of electrostatic interactions and surface energy rather than charge transfer in antibacterial properties ( Zurob et al, 2019 ). The performance of CVD hBN and graphene coatings in preventing cellular adhesion are shown in Figure 8 .…”

“…Graphene and hBN have been recently found to induce specific cellular responses in different contexts. Taking into consideration the issues related to bacterial infection and the relevance of degenerative diseases, the different biological interactions of these materials can be exploited toward the following aims: (1) inducing bacterial cell death, e.g., to design medical instruments and mitigate the spreading of infections in hospital environment, and to produce anti-biofouling coatings ( Parra et al, 2015c , 2017 ; Zurob et al, 2019 ); (2) stimulating cellular growth, such as in the case of tissue engineering, wound healing, and bone tissue regeneration ( Fernandes et al, 2019 ; Şen et al, 2019 ; Aki et al, 2020 ). Devices such as epidermal electronics, intra-cortical implants for sensing and brain tissue regeneration require intimate contact with biological systems.…”

Two Type VI Secretion Systems of Enterobacter cloacae Are Required for Bacterial Competition, Cell Adherence, and Intestinal Colonization

“…E. cloacae is a human opportunistic pathogen that is frequently associated with hospital-acquired infections of the lower respiratory tract, urinary tract, and meninges (Liu et al, 2013). Despite the relevance of E. cloacae as a nosocomial pathogen, its pathogenicity mechanisms are not yet fully understood, but biofilm formation is a virulence feature of this opportunistic microorganism (Zhou et al, 2014;Zurob et al, 2019). In addition, some E. cloacae strains possess cytotoxic activity, suggesting the secretion of bacterial toxins to the cell host (Barnes et al, 1997;Krzyminska et al, 2009).…”