The effect of silver nanoparticles on Staphylococcus epidermidis biofilm biomass and cell viability



1 Students Research Committee, Ph.D. Candidate, Department of Food and Drug Control, School of Pharmacy, Mashhad University of Medical Sciences, Mashhad, Iran

2 Students Research Committee, School of Pharmacy, Mashhad University of Medical Sciences, Mashhad, Iran

3 Biotechnology Research Center, School of Pharmacy, Mashhad University of Medical Sciences, Mashhad, Iran


Bacterial biofilm has been considered responsible for many deaths and high health costs worldwide. Their better protection against antibacterial agents compared to free living cells leads to poor treatment efficiency. Nanotechnology is promising approach to combat biofilm infections. The aim of the present study was to eradicate Staphylococcus epidermidis biofilm with silver nanoparticles (SNPs).
Materials and Methods:
SNPs were used at different concentrations (two fold dilutions) and incubation times (24, 48, 72 h). The crystal violet staining and pour plate assays were used to assess biofilm biomass and bacterial viability, respectively. The ability of SNPs on biofilm matrix eradication was assessed through optical density ratio (ODr). Positive control was defined as an ODr =1.0.
The crystal violet assay indicated that the biofilm matrixes were intact at different concentrations of SNOs and incubation times. There were no significant differences between these parameters (P >0.05). Bacterial enumeration studies revealed that higher concentrations of SNPs were more effective in killing bacteria than lower ones. Although, longer incubation times  led to enhancement of anti-biofilm activity of SNPs.

The anti-biofilm activity of SNPs was concentration- and time-dependent. The results of this study highlighted that SNPs were effective against cell viability; however they were ineffective against biomass.


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