Comparison of direct and transferred cold atmospheric discharge in long, flexible tubes for the decontamination and removal of Pseudomonas aeruginosa biofilms

Abstract 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.