Silicon nanoparticles: A promising approach for control of Pseudomonas aeruginosa biofilms

Abstract

Objectives: The current study aimed to investigate the control and treatment of biofilm-producing isolates of Pseudomonas aeruginosa using silicon nanoparticles (SiNPs).

Materials and methods: Biofilm-producing isolates of P. aeruginosa were recovered from various food samples and identified through fluorescent green colony formation on selective and differential media, as well as the amplification of oprI and oprL genes. Tube methods, Congo-red agar method, and scanning electron microscopy (SEM) were used to study biofilm phenotypes. The effect of SiNPs was evaluated by broth dilution assay.

Results: The biofilm assay revealed that these isolates formed biofilms on glass surfaces within 72 hr of incubation. Scanning electron micrographs showed that the biofilm communities were composed of multicellular clusters of P. aeruginosa encased in matrix material. However, these isolates were unable to form biofilms on SiNPs-coated surfaces. The results showed that the planktonic isolates of P. aeruginosa were comparatively sensitive to the antibacterial properties of SiNPs, with minimum inhibitory concentration (MIC) ranging from 100 to 200 µg/ml. Contrarily, the biofilms were found to be 500 times more tolerant to the highest concentration of SiNPs (MIC of 500 µg/ml) and were more resistant. Under static conditions, the sedimentation of SiNPs resulted in their ineffectiveness. However, under shaking conditions, the biofilms were effectively dispersed and the cells were lysed. The results showed that SiNPs were effective against both the planktonic and the metabolically inactive forms of P. aeruginosa.

Conclusion: This study suggests that SiNPs could be a useful tool for preventing the formation of biofilms and removing pre-existing biofilms.

Keywords: Biofilms; Nanoparticles; Pseudomonas aeruginosa; SiNPs; Silicon.

Figure 1

Comparison of MIC of SiNPs against pre-biofilm and biofilm stages of Pseudomonas aeruginosa

Figure 2

MIC of Pseudomonas aeruginosa biofilm formation over time

Figure 3

The graph shows the effect of SiNPs (500 µg/ml) on Pseudomonas aeruginosa population/CFU with exposure time and shaking at 200 rpm

Figure 4

Effect of SiNPs (500 µg/ml) on the biofilm population of Pseudomonas aeruginosa in static conditions is shown in this figure

Figure 5

Scanning electron micrograph of Pseudomonas aeruginosa biofilm on glass slides

Figure 6

Scanning electron micrograph of biofilm on SiNPs-coated slides

Figure 7

(a & b) Scanning electron micrographs showing the presence of SiNPs surrounding Pseudomonas aeruginosa cells, and the formation of micro-pores in nearby cells. (c &d) The EDS spectra are confirming the presence of SiNPs

Figure 8

SEM image of dead cells attached to the surface after exposure to SiNPs