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This paper reports the efficacy of nonthermal plasma (NTP) as a biocidal agent to treat 304 stainless steel (SS304) covered with a diamond-like carbon (DLC) film contaminated with Candida albicans biofilms. The association of two techniques using electric plasma was used. The first was plasma-enhanced chemical vapor deposition (PECVD) used to deposit a DLC film on the SS304. The second was NTP used on the surface of the SS304 with and without the DLC film. The combination of the SS304 surface with the DLC film was demonstrated to be effective when using the DLC film as corrosion protection. Comparing the proliferation of Candida species on the DLC film and SS304 surface, it was possible to conclude that Candida species stays longer in the DLC film than in SS304. The reduction of colony numbers was visible after 5 min using plasma on both surfaces; in addition, 99% of Candida species were eliminated after 15 min. Three C. albicans microorganisms were used. Two were from samples of urine and tracheal secretion, and one was from the American Type Culture Collection (ATCC #90028). Characterization of the plasma chemical species was performed using optical emission spectroscopy in order to understand the nature of the chemical species that inactivated the microorganisms. The DLC film was analyzed using profilometry, Raman spectroscopy, scanning electron microscopy, and tribocorrosion tests. The tribocorrosion tests were used to evaluate the effectiveness of the DLC film in protecting the SS304 surface against corrosion in simulated body fluid because corrosion species from the SS304 could interfere in biofilm growth and mask the effect of the plasma. The results of the factorial analysis of variance confirmed the statistical significance (p > 0.05) of the plasma as a biocidal agent, considering the reduction of colony-forming units of C. albicans. It was found that exposure of the samples to the plasma for only 5 min resulted in reductions ranging from 96.4 to 100.0% for all the microorganisms studied.

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In this paper, a diamond-like carbon (DLC) film with a controlled content of hydrogen (20%) and carbon (80%) was deposited onto a 304 stainless steel (304SS). Tribocorrosion tests were performed following immersion in simulated body fluid (SBF) solution. The DLC film with hydrogen and carbon control decreased the SS304 corrosion susceptibility 59-fold, compared to the bare surface, improving on the corrosion protection provided by DLC reported in the literature. Debris or nanoparticles from corroded metals can cause cytotoxicity or genotoxicity towards many cells, so these possible effects were evaluated using A172 glial cells (ATCC #CRL-1620 glioblastoma). The DLC film was not genotoxic or cytotoxic towards the glial cells. Furthermore, no cytotoxicity or genotoxicity was observed in the A172 cells after exposure to the SS304 covered with DLC film, even after 24 h of incubation, when compared to untreated cells. The methodology adopted, using a silicon interface between the DLC and the 304SS, was effective in preventing delamination of the DLC film. This report provides full information concerning methods for the production and characterisation of this DLC film.

Stainless steel 316L (SS316L) and titanium-alloy Ti6AL4V exhibit properties for bio-medical applications; however their tribocorrosion associated with metallosis is still a major concern. Therefore smoothing DLC coatings aiming for the improvement of tri-bocorrosion and cell viability of stainless steel 316L (SS316L) and titanium-alloy Ti6AL4V with and without DLC coatings were compared. The motivation was due to many papers detailing metallosis caused by metal debris in the body's soft tissues. Nowadays, metallosis is responsible for almost of prosthesis replacement surgeries. DLC coatings were produced using the Plasma Enhanced Chemical Vapor Deposition (PECVD) technique; acetylene gas was used as a carbon precursor, and silane gas produced an amorphous silicon interface between the DLC coating and metal substrate. A combined setup of techniques thoroughly evaluated the coatings considering chemical composition, coatings adhesion at a metallic substrate, scratch resistance, and tribocorrosion susceptibility. The cytotoxicity and genotoxicity of metallic samples with and without DLC coatings were analyzed, considering cell viability and its correlation with coatings’ chemical composition