Antoine Remy

Endoscope working channels are particularly vulnerable to bacterial contamination and biofilm formation due to repeated exposure to biological fluids and limited sterilization options. Inadequate reprocessing can lead to the formation of persistent biofilms and the transmission of healthcare-associated infections. To address this, we investigate the use of cold atmospheric plasma (CAP) generated directly inside endoscope-like Polytetrafluoroethylene (PTFE) tubing to improve decontamination and biofilm removal. This study compares two dielectric barrier discharge (DBD) configurations: a one discharge tube (ODT), in which the plasma is generated directly inside the contaminated tube, and a two discharge tube (TDT), where a high-power upstream discharge supplies reactive species to a second discharge within the tube, also called transferred discharges. Both systems were evaluated using 2 cm samples of PTFE tube colonized with Pseudomonas aeruginosa biofilms, using the Pineau-Alfa model. Several gases or gas mixtures (He, Ar, He/O ₂ , Ar/H ₂ O, He/H ₂ O, and air) were tested. The discharges were characterized using electrical measurements, optical emission spectroscopy, Fourier transform infrared spectroscopy FTIR, and H ₂ O ₂ quantification to analyze the production of reactive oxygen and nitrogen species (RONS). All gas conditions except TDT–air achieved full bacterial decontamination within 5 min. However, biofilm removal was limited, with the most effective condition (ODT–He/H ₂ O) reducing biofilm coverage on the surface by 29 ± 6%. The ODT configuration provided superior local RONS delivery, including atomic oxygen and OH radicals. Its simpler design and the direct contact of the discharge with the contaminated surfaces present significant advantages for implementation in clinical settings, while maintaining the same decontamination capabilities. These findings confirm the feasibility of CAP-based in-situ decontamination for long, flexible medical tubing. Further optimization of discharge parameters and treatment time is required to enhance biofilm removal and achieve single-step, residue-free reprocessing of endoscopic devices while eliminating the reliance on hazardous chemicals (e.g. ethylene oxide, glutaraldehyde) or disposable endoscopes.

In medical device disinfection, removing bacteria and biofilms is challenging due to the poor penetration of detergents into the biofilm matrix. This is specifically true for endoscopes, which cannot be fully sterilized. This paper presents a new technique for decontaminating and removing P. aeruginosa biofilm from endoscope tubing using cold atmospheric plasma (CAP). The CAP is produced everywhere inside a contaminated tube under sustained Ar/H₂O flow. The tube arrangement mimics the working channel environment of an endoscope, which is particularly difficult to sterilize. The discharge’s chemical activity was optimized by increasing the voltage without increasing the total power, which enhanced the production of hydroxyl radicals (OH) and hydrogen peroxide (H₂O₂). The disinfection treatment was tested on 24 h grown biofilm using the crystal violet assay for biofilm removal and the regrowth assay for bacterial decontamination. The treatments demonstrated effective decontamination capabilities at all treatment times with no bacterial regrowth. Etching of the biofilm sample by OH radicals was observed. After 30 min of treatment, only 18 ± 4% of biofilm remained on the surface, indicating near-complete biofilm removal and total absence of bacterial regrowth. This preliminary study demonstrates the effectiveness of using the direct contact of an Ar/H₂O plasma to decontaminate and remove biofilm from complex shapes, such as flexible polytetraethylene tubes. It has the potential to enhance and shorten the disinfection of medical equipment, such as endoscopes.

The one-step deposition of spatially differentiated crystalline vanadium oxide coatings (V2O5) using an atmospheric pressure dielectric barrier discharge is reported. This feasibility study uses an original combination of immobilized filaments inside the plasma and an inductive heating device. Preliminary results show that thick crystalline deposits are achieved under the immobilized filaments, whether the interfilament spacing leads to much thinner deposits, with a different chemical composition. The gas flow inside the reactor, combined to the filament reactivity, leads to local depletions of reactants.

Pursuing more efficient nitrogen fixation in the context of the current climate crisis is of prime importance. The Haber‐Bosch process (NH₃ production) accounts for at least 2% of the yearly released greenhouse gases. Alternatively, different atmospheric nonthermal discharges have proven their ability to convert nitrogen and oxygen from the air into nitrogen oxides (NO, NO₂, and HNO₃ hereafter referred as NO_x). Among them, dielectric barrier discharges (DBDs) in N₂/O₂ are very interesting as they are characterized by microdischarges (MDs) developing into filaments under specific conditions (gap length, voltage, frequency, nature of the dielectrics). In this work, we used a sinusoidal voltage at 4, 12, 17.5, and 30 kHz as a key parameter to manipulate the MDs behaviors in an N₂/O₂ DBD and tailor the chemistry of the discharge. We characterized the MDs distribution by high‐speed camera imaging. Two different nitrogen emission systems, that is, the second positive system (SPS) and the first negative system (FNS), were used to assess the filament temperature and what we define as the delayed‐glow temperature, respectively. The influence of the filament's distribution on the overall discharge temperature has also been evaluated, by using a novel approach allowing the generation of heat distribution maps directly on a thermosensitive paper exposed to the discharge. Finally, the effect of the filaments on ozone (O₃) and NO_x production has been monitored by in situ Fourier‐transform infrared (FTIR). The DBD can be tuned between homogenously distributed MDs at 4 and 12 kHz to highly localized filaments at 17.5 and 30 kHz. A high filament temperature combined with a cold delayed‐glow is observed at 17.5 kHz while both the filament and the delayed‐glow temperature are high at 30 kHz. Low frequencies lead to heat spreading into the whole discharge volume, while localization of heat along the filament's paths is observed at high frequencies. High‐temperature filaments in the 30 kHz discharge and in the globally heated discharge at low frequencies quickly remove O₃ from the discharge and consequently limit the overall NO_x production by removing important oxidation pathways. On the contrary, filaments surrounded by cold gas observed at 17.5 kHz allowed to maintain a high concentration of O₃ necessary for a faster oxidation of NO and thus increase the HNO₃ production, even after 250 s, by avoiding backward reactions.