Biofilm inactivation by synergistic treatment of atmospheric pressure plasma and chelating agents

In this study, we investigated the bacterial biofilm reduction by combined treatment of atmospheric pressure plasma (APP) and chelating agents. Many of hospital acquired infections (HAI) are related to biofilm infections. APP and chelating agents were reported to be effective in bacterial biofilm inactivation and eradication. It is believed that chelating agents disrupt the biofilm formation through bonding metal ions, while APP inactivates bacteria mainly through reactive species [1–3]. In our study, we used a surface micro-discharge (SMD) driven by sinusoidal power input of 2 kHz and peak to peak voltage of 9 kV to treat Escherichia coli (E. coli), Enterococcus faecalis (E. faecalis), and Staphylococcus capitis (S. capitis) biofilm on 316 L stainless steel and hopkins rod lens glass plates in combination with chelating agents of trisodium citrate (TSC), ethylenediaminetetraacetic acid (EDTA), egtazic acid (EGTA), and alizarin. Bacterial biofilm reduction was measured by means of colony count assay and BacTiter-Glo cell viability assay. The results of colony count assay showed that combined treatment of EDTA and TSC with plasma has synergistic effects on all three bacterial biofilms, while EGTA only on E. coli and none for alizarin. Experiments of BacTiter-Glo cell viability assay indicate that EDTA, EGTA, and TSC has synergistic effects on all three biofilms while also none for alizarin.