Plasma-fungal biofilm interaction: diagnostic of the plasma and inactivation process of the Candida spp strains

Abstract

Fungal biofilms represent a constant and predominant cause of chronic infections which can be associated with the use of medical devices for a long period, such as catheters and prostheses. Such infections exhibit a significantly increased tolerance to antifungal, biocidal agents and immunological changes. This makes it difficult, and sometimes impossible, to treat with conventional therapeutic agents. Atmospheric pressure non-thermal plasmas are gaining increased attention as a potential approach to the eradication and control of infection and / or bacterial or fungal contamination, however, with regard to fungal contamination, many factors related to these processes need to be further discussed. In this work, different types of plasmas operated at atmospheric pressure will be applied in the process of inactivation of biofilms of Candida yeasts grown in vitro on polyurethane and silicone elastomer substrate, main components of venous catheters. The effects of plasma chemistry, plasma operating frequency and operating time in plasma biofilm interaction and consequently the antifungal activity will be investigated. For this, the study will be divided into three experimental steps: (i) plasma diagnostics through molecular beam mass spectrometry, optical emission spectroscopy, and electrical characterization; (ii) analysis of the morphology of biofilms/substrate before and after plasma treatment by scanning electron microscopy and atomic force microscopy; (iii) determination of the amount of colony forming units (CFU/ml) and cell viability by fluorescence microscopy, before and after treatment to evaluate the antifungal activity of the tested plasmas. Finally, we intend to correlate the experimental analysis of this study with results of theoretical modeling developed for plasma-biological surface interaction in order to better explain the observed phenomenology and thus contribute to the areas of biomedical engineering and plasmas applied to biological processes, that is new branch in the international scientific literature and, in particular, in Brazil.