Electron density measurement and VUV/UV emission spectroscopy in a low pressure low temperature RF plasma confined inside sterilization pouches for the sterilization of medical devices

Plasma characterization and biological tests In the world, 1.4 million persons suffer from infectious complications acquired in hospital1. Sterilization of medical devices are crucial to world public safety. Conventional sterilization methods (moist heat, ionizing irradiation and chemical treatment) are not compatible with the most recently developed materials because of the poor resistance of some sensitive materials to sterilizing agents. New sterilization techniques using glow discharge2,3 plasma and afterglow discharge4,5 plasmahave been studied by several research groups. In the framework of the PLAS’STER project, a prototype based on a RF plasma confined inside sterilization pouches for the treatment of medical devices has been developed.In our process, the medical device to be sterilized is placed in a special medical sealed pouch allowing a gas flow such as Argon, Nitrogen and Oxygen. The pouch is set on the power electrode. By tuning the pressure difference between the reactor chamber and the pouch, the plasma is kept confined inside the pouches. The major advantage of dealing with packaged medical devices is to preserve their on-self sterility without any additional precautions before further use. Optical Emission Spectroscopy (OES) was used to study the plasma emission from VUV/UV to IR wavelengths range. Beside typical emission of the feed gas such oxygen atomic in oxygen plasma, several emissions are due to impurities and to the reaction of the plasma with the surrounding pouch. Chemical measurements have detectedsmall surface modifications on pouches wall without altering barrier properties. Plasma electron density has been measured by microwave interferometry (MWI) between 1.108 cm-3 and 2,9.109 cm-3 depending on the gas and the RF power. By coupling MWI and OES diagnostics, the variation of the argon 750,4 nm line intensityin function of RF power have shown the same trend as the electron density. The effectiveness of our process has been demonstrated for sterilization with bacteriological tests performed EA4691 BIOS Laboratory. A 6log reduction on Pseudomonas aeruginosa was obtained in 45 minutes in different gases. Acknowledgements This work is supported by the ANR-12-TECS-0007 project PLAS’STER. References [1] D. Pittet, J. Hospital Infection, 68, 285-292 (2008) [2] F. Rossi, Pure Appl. Chem., 80, 9, 1939-1951 (2008) [3] P. Levif, Plasma Process. Polym, 8, 617-630 (2011) [4] M. Moisan, J. Phys. D : Appl. Phys., 47, 285404 (2014) [5] J-P. Sarrette, Plasma Process. Polym., 9, 576-584 (2012)