Bacterial spore inactivation by atmospheric-pressure plasmas in the presence or absence of UV photons as obtained with the same gas mixture
Bacterial spore inactivation by atmospheric-pressure plasmas in the presence or absence of UV photons as obtained with the same gas mixture
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DOI：
10.1088/0022-3727/39/16/s07
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发表时间：
2006-08-21
影响因子：
3.4
通讯作者：
Massines, F.
中科院分区：
文献类型：
--
作者：
Boudam, M. K.;Moisan, M.;Massines, F.
本文件包括两个主要部分：综述了用于微生物灭活的大气压放电的文献，重点是灭活机制，并介绍了我们的研究结果，特别是，紫外线光子可以是灭活过程中的主要物种。使用大气-压力放电或其流动的余辉是持续争论的对象。事实上，我们目前的文献回顾表明，大多数研究人员已经得出结论，在大气压下，化学反应性物种，如自由基，亚稳态原子和分子总是控制灭活过程，而紫外光子只起次要作用或根本没有作用。与此相反，只有少数文章建议或声称，来自大气压放电的紫外光子可以，在某些情况下，杀灭微生物，但在这方面提出的实验数据和提出的支持论据是相对不完整的。实验中，微生物经受等离子体条件，使得一方面UV辐射强，或者另一方面没有UV辐射，这两种不同的情况用相同的实验装置获得，包括相同的气体混合物N2-N2 O。为了实现最大的紫外线辐射，需要仔细调整添加到N-2中的氧化剂分子（N2 O）的浓度，从而获得最快的灭活速率。混合物中氧化剂分子的浓度范围（对于该浓度范围，UV强度是显著的）非常窄，这一事实可能解释了为什么不容易观察到这种等离子体灭菌模式。在主要的紫外线辐射条件下获得的生存曲线，如我们所示，类似于在减压下记录的那些。在没有紫外线辐射的情况下，由于自由基在孢子内部扩散，导致氧化致死性损伤，也可以获得相对快速的孢子灭活。
This paper comprises two main parts: a review of the literature on atmospheric-pressure discharges used for micro-organism inactivation, focused on the inactivation mechanisms, and a presentation of our research results showing, in particular, that UV photons can be the dominant species in the inactivation process.The possibility of achieving spore inactivation through UV radiation using an atmospheric-pressure discharge or its flowing afterglow is the object of a continuing controversy. In fact, the review of the literature that we present shows that a majority of researchers have come to the conclusion that, at atmospheric pressure, chemically reactive species such as free radicals, metastable atoms and molecules always control the inactivation process, while UV photons play only a minor role or no role at all. In contrast, only a few articles suggest or claim that UV photons coming from atmospheric-pressure discharges can, in some cases, inactivate micro-organisms, but the experimental data presented and the supporting arguments brought forward in that respect are relatively incomplete.Using a dielectric-barrier discharge operated at atmospheric pressure in an N-2-N2O mixture, we present, for the first time, experiments where micro-organisms are subjected to plasma conditions such that, on the one hand, UV radiation is strong or, on the other hand, there is no UV radiation, the two different situations being obtained with the same experimental arrangement, including the same gas mixture, N-2-N2O. To achieve maximum UV radiation, the concentration of the oxidant molecule (N2O) added to N-2 needs to be tuned carefully, resulting then in the fastest inactivation rate. The concentration range of the oxidant molecule in the mixture for which the UV intensity is significant is extremely narrow, a fact that possibly explains why such a mode of plasma sterilization was not readily observed. The survival curves obtained under dominant UV radiation conditions are, as we show, akin to those recorded at reduced pressure. Relatively fast spore inactivation can also be obtained under no UV radiation as a result of radicals diffusing deeply inside the spores, leading to oxidative lethal damage.