Effect of gas composition on spore mortality and etching during low‐pressure plasma sterilization

Abstract

The aim of this work was to investigate possible mechanisms of sterilization by low-temperature gas plasma: spore destruction by plasma is compared with etching of synthetic polymers. Bacillus subtilis spores were inoculated at the bottom of glass vials and subjected to different plasma gas compositions (O(2), O(2)/Ar, O(2)/H(2), CO(2), and O(2)/CF(4)), all known to etch polymers. O(2)/CF(4) plasma exhibited much higher efficacy than all other gases or gas mixtures tested, with a more than 5 log decrease in 7.5 min, compared with a 2 log decrease with pure oxygen. Examination by scanning electron microscopy showed that spores were significantly etched after 30 min of plasma exposure, but not completely. We speculate about their etch resistance compared with that of synthetic polymers on the basis of their morphology and complex coating structure. In contrast to so-called in-house plasma, sterilization by Sterrad(R) tended to increase the observed spores' size; chemical modification (oxidation), rather than etching, is believed to be the sterilization mechanism of Sterrad(R).

Low-pressure water vapour plasma treatment of surfaces for biomolecules decontamination

“…Such a phenomenon was already reported [38] for oxygen containing discharges, and it was attributed to the increasing density of nonvolatile compounds (e.g., calcium, sodium, etc) on the spores' external surfaces, forming an etching-resistant layer; the same process was also recently investigated on protein films' model contaminations [32].…”

Plasma-surface modification of biomaterials

“…They discover that: (i) plasmabased sterilizers induce limited oxidation at the near-surface layer, (ii) molecular weights are not changed after plasma-based sterilization, (iii) the hydrolytic stability of catheters is only slightly changed by plasma-based sterilization with a small increase in released oligomers, and (iv) different plasma-based sterilization techniques result in different impacts on the catheters, such as the degradation of an additive or a clear difference in coloration [147]. Lerouge et al investigate the possible mechanism of plasma sterilization by low-temperature gas-plasma and believes that chemical modification (oxidation), rather than etching, is the sterilization mechanism of STERRAD TM [148]. Holy et al employ a novel poly (lactide-co-glycolide) scaffold (Osteofoam TM ) to determine the optimal sterilization procedure, and then compare three sterilization techniquesrfGD plasma sterilization, ETO, and g-irradiation in terms of their immediate and long-term effects on the dimensions, morphology, molecular weight, and degradation profile of the scaffolds [144].…”

Sterilization Effect of Wet Oxygen Plasma in the Bubbling Method

“…Many studies have shown that various gases such as argon, oxygen, nitrogen or hydrogen peroxide have sporicidal activity Griffiths 1993;Crow and Smith, 1995;Feldman et al, 1997;Soloshenko et al, 2000, Montie et al, 2000Lerouge et al, 2000a;Lerouge et al, 2000b;Moisan et al, 2001;Tamazawa, 2004;Stoffels et. al., 2004;Shintani et al, 2007 .…”