New plasma sterilization process for packaged medicaldevices: plasma diagnosis and medical pouch characterization

Nowadays, the fight against nosocomial infections is a priority for all healthcare systems [1]. Whereas the conventional methods have shown limitations for the sterilization of innovative materials owing to the high temperature or toxic products [2], low pressure plasma provide a good alternative, safe for users and materials [3]. In this context, a newly designed plasma sterilization process ensuring the preservation of the sterile state has been developed in the framework of the PLAS’STER project. The plasma is only produced and confined inside a sterilization pouch containing the medical devices to be sterilized. Optical Emission Spectroscopy measurements from vacuum ultraviolet to infrared have shown intense VUV/UV emissions below 300 nm related to the production of reactive species such as N*, O*, NO* and OH* in the three employed gases (Ar, N2, O2). Microbiological results have demonstrated the efficiency with a 6log reduction on Gram-positive and Gram-negative bacteria during periods competitive with conventional methods (e.g. P. aeruginosa and S. aureus). To distinguish the potential bactericidal role of plasma species, bacteriological tests using MgF2 optical filters have been performed. Microwave interferometry was employed to estimate the electron density as a function of different parameters. An increase of ne from 1.108 to 2,9.109 cm-3 with the applied RF power and the magnetic field was measured. Moreover, a perfect agreement in the trend followed by the ne evolution and the Ar 750,4 nm line intensity variation as a function of RF power in Ar-discharge was observed, allowing to monitor the ne variation by following the argon line in our experimental set-up. The sterile state preservation is closely linked to the medical pouch properties after plasma treatment. In this regard, Fourier Transform Infrared Spectroscopy and X-ray Photoelectron Spectrometry analysis combined with contact angle measurements were performed immediately and during two weeks after treatment. Under optimal sterilization conditions, no change of the macromolecular structure were observed. In addition, the slight grafting of N and O atoms which have been highlighted on the extreme surface by XPS don’t affect the pouch integrity. The water contact angle variation as a function of the aging time have showed a recovery to the initial hydrophobicity after 6 hours following the treatment. Acknowledgements This work is supported by the ANR-12-TECS-0007 project PLAS’STER. References [1] D. Pittet et al., “Infection control as a major World Health Organization priority for developing countries,” pp. 285–292, 2008. [2] W. a. Rutala and D. J. Weber, “Disinfection and sterilization: An overview,” Am. J. Infect. Control, vol. 41, no. 5 SUPPL., pp. S2–S5, 2013. [3] a. Von Keudell et al., “Inactivation of bacteria and biomolecules by low-pressure plasma discharges,” Plasma Process. Polym., vol. 7, no. 3–4, pp. 327–352, 2010.