Surfatron-produced atmospheric-pressure plasma jet applied to candida biofilms

Abstract

Fungal biofilms represent a constant and predominant cause ofchronic infections. They exhibit increased tolerance to antifungal agents and immunological variations, making them difficult to treat with conventional therapeutic agents. The technology of nonthermal plasmas at atmospheric pressure has been increasingly used in studies aimed at eradication and control of fungal contamination. Here, we evaluate the action of a plasmajet that is generated by a surfatron source, using different gas compositions on polyurethane (PU) samples that are contaminated with biofilms of Candida albicans and Candida parapsilosis. Samples were treated using plasma with 4 standard liters per minute (SLM) argon + 6 SLM air in 100 W of applied power (group 1), 4 SLM argon + 9 SLM argon with water vapor in 50 W (group 2), and 4 SLM argon + 9 SLM argon with water vapor in 150 W (group 3). We performed treatments in the postdischarge region (30 mm) for 10 min. We characterized plasmas using optical emission spectroscopy and scan­ning electron microscopy on samples by infrared images of the surface during plasma treatment, determining colony-forming units (CFU) and surface morphology. Results showed that for C. albicans, groups 1 and 3 plasmas were reduced by 100%, whereas for C. parapsilosis, groups 2 and 3 showed reductions of 92.41% and 97.85% CFU/mL, respectively. Morphological changes were observed in the biofilm cells, and thermal analyses of substrate surface showed that process parameters were adequate to control Candida contamination, because parameters resulted in a small increase in PU surface temperature (< 40°C) during sterilization.