The impact of titanium oxide nanoparticles and low direct electric current on biofilm dispersal of $Bacillus~cereus$ and $Pseudomonas~aeruginosa$: A comparative study

Mamdouh M Shawki,Maisa E Moustafa,Marwa M Eltarahony

doi:10.4279/pip.130005

Mamdouh M Shawki, Maisa E Moustafa + Show 1 more

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https://doi.org/10.4279/pip.130005

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Abstract

Bacteria growing in biofilms cause a wide range of environmental, industrial and public health risks. Because biofilm bacteria are very resistant to antibiotics, there is an urgent need in medicine and industry to develop new approaches to eliminating bacterial biofilms. One strategy for controlling these biofilms is to generate an antibiofilm substance locally at the attachment surface. Direct electric current (DC) and nanoparticles (NPs) of metal oxides have outstanding antimicrobial properties. In this study we evaluated the effect of titanium oxide nanoparticle (TiO$_2$-NP) concentrations from 5 to 160 $\mu$g/mL on Bacillus cereus and Pseudomonas aeruginosa biofilms, and compared this with the effect of a 9 V, 6 mA DC electric field for 5, 10 and 15 min. TiO$_2$-NPs were characterized using transmission and scanning electron microscopes, X-ray diffraction and FTIR. They exhibited an average size of 22-34 nm. The TiO$_2$-NP concentrations that attained LD50 were $104 \pm 4$ $\mu$g/mL and $63 \pm 3$ $\mu$g/mL for B. cereus and P. aeruginosa, respectively. The eradication percentages obtained by DC at 5, 10, and 15 min exposure were 21%, 29%, and 33% respectively for B. cereus and 30%, 39%, and 44% respectively for P. aeruginosa. Biofilm disintegration was verified by exopolysaccharide, protein content and cell surface hydrophobicity assessment, as well as scanning electron microscopy. These data were correlated with the reactive oxygen species produced. The results indicated that both DC and TiO$_2$-NPs have a lethal effect on these bacterial biofilms, and that the DC conditions used affect the biofilms in a similar way to TiO$_2$-NPs at concentrations of 20-40 $\mu$g/mL.

Highlights

Bacterial biofilms are clusters of bacteria that are attached to a surface and/or to each other and embedded in a self-produced matrix [1]
The results indicate that both Direct electric current (DC) and TiO2-NPs have a lethal effect on these bacterial biofilms, and that the DC conditions used affect the biofilms in a similar way to TiO2-NPs at concentrations of 20–40 μg/mL
Poortinga et al [48] reported electrical detachment of biofilm formations from surgical implants, while Van der Borden et al [49] demonstrated that DC of only 25–125 mA can stimulate detachment of staphylococcal strains from stainless steel, Del Pozo et al [14] recorded a decrease in the viability of S. aureus, S. epidermidis and P. aeruginosa biofilms after prolonged exposure to a low-intensity electrical current of 20–2000 mA

Summary

Introduction

Bacterial biofilms are clusters of bacteria that are attached to a surface and/or to each other and embedded in a self-produced matrix [1]. The biofilm matrix consists of extracellular polysaccha-. Compared with planktonic forms, organisms in biofilms resist undesirable physical, chemical and biological factors in the environment, host immune system, and antimicrobial therapy [3]. The susceptibility of bacteria in biofilms to antimicrobial agents is 500–5000 times lower than that of bacteria in suspension (planktonic) cells of the same microorganism [4]. This resistance is due to restricted penetration of the biofilm matrix, the presence of antimicrobial enzymes, an altered growth rate inside the biofilm, a stress response to unfavorable environmental conditions, and over-expression of genes [5].

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