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CHAPTER 1 PRINCIPLES OF SURFACE DISINFECTION 1.1 Introduction AND STERILIZATION The development of sterilization concepts has a long history starting from the end of 19 th century when the first rules for controlling the spreading of pathogen agents were established [1]. Boiling of the medical instruments and the first steam sterilizer has been introduced in the 1880 0 s [1, 2]. Not much latter, the concept of non-thermal sterilization method for food, drinks and materials preservation has gained more attention. Therefore, chemical gas and liquid disinfectants were adopted as low temperature alternatives. The most common chemical sterilant, still intensively used nowadays, is the ethylene oxide gas which has been introduced in hospitals and medical industry starting with 1940. [1,3]. The application area for pathogens destruction has not been covered only by thermal and chemical methods. The decontamination potential of the electromag- netic radiation as for example gamma or X rays irradiation was tested starting with the second half of the last century [1]. Not much latter, electrical gas dis- charges were introduced as an original approach suitable for microbial inactivation 1
and intuited to bring new important benefits in this area. Nowadays, due to the continuous growth of the interest for finding more robust and effective sterilization techniques, the conceptual basis of this research topic are much better established. Altogether, a number of rules for contaminated medical pieces with pathological microorganisms have been imposed, mostly of them derived from daily practice and limitations of the commonly used techniques. Hence, standardized procedures and methods have come as a consequence and accepted as sterilization and disinfection principles [4-6]. Definition 1 Cleaning is the act of removal of undesirable elements from an object. These undesirable elements can be any kind of impurities. If the impurities are microorganisms (microscopic life-form with dimension of few microns) the object is said to be, in medical terms, as infected [7, 8]. Consequently, the cleaning of such an object is called disinfection. However, during the disinfection process the microorganisms are simply removed and let alive, as can be in the case of cleaning, but inactivated [7-9]. Definition 2 Inactivation of a microorganism is the process of stopping its nat- ural activity by function-altering or destruction (i.e., killing). Under these circumstances, a clear definition of disinfection can be given: 2
Page 1 and 2: PLASMA STERILIZATION USING LOW PRES
Page 3 and 4: my appreciation especially for the
Page 5 and 6: Iis ion saturation current [µA] t
Page 7 and 8: CONTENTS 1 PRINCIPLES OF SURFACE DI
Page 9: 4 EFFECTS OF LOW TEMPERATURE PULSED
Page 13 and 14: Figure 1.1: Schematic representatio
Page 15 and 16: Table 1.1: Common disinfection and
Page 17 and 18: the radiation energy is resonantly
Page 19 and 20: ers of heat, optical radiation and
Page 21 and 22: Table 1.2: Main plasma sources used
Page 23 and 24: microorganism population as a respo
Page 25 and 26: UV Photon Before After DNA Figure 1
Page 27 and 28: to sterilize medical tools, but the
Page 29 and 30: sented by both theoretical and expe
Page 31 and 32: Plasma Sterilization Using Low Pres
Page 33 and 34: Figure 2.1: Experimental set-up. MB
Page 35 and 36: Figure 2.3: Electronic circuit of t
Page 37 and 38: such circumstances, the inactivatio
Page 39 and 40: ment time t is N = N0e −αt ≡ N
Page 41 and 42: shows the number of the viable micr
Page 43 and 44: has n −1 0 > 281.25 µm 2 availab
Page 45 and 46: 1 st 2 nd ( I) TNTC (II) TNTC (III)
Page 47 and 48: U LC blocking filter 19.74 pF 20.24
Page 49 and 50: Figure 2.8: Experimental set-up use
Page 51 and 52: the reactive species from plasma ar
Page 53 and 54: Temperature measurement Relative in
Page 55 and 56: MR MP SH Figure 3.2: Experimental a
Page 57 and 58: a fast temperature increasing rate.
Page 59 and 60: D h (min) 10 3 10 2 10 1 10 0 100 2
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MR QP SH Figure 3.6: Experimental a
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The contribution of photons and hea
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D (min) 10 3 10 2 10 1 10 0 Dν D h
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N/N 0 (%) 10 2 10 2 10 2 10 2 10 2
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D (min) 10 2 10 1 10 0 D h+ν+p D h
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holder is mainly given by particle
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3.5 Power sensitivity of spore inac
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If for a reference treatment temper
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of the sample was achieved. Moreove
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microorganisms were disposed in mon
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The pulse period covered a wide int
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in chapter 2. The treatment time of
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4.2.2 Injected RF power In order to
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ton =500µs, and the duty cycle was
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T ( 0 C) 120 100 80 60 40 20 I 0 5
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N/N 0 (%) 10 2 10 2 10 2 10 1 10 1
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elow 70 ◦ C. 3. Increasing the in
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the second phase of the inactivatio
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k 1, 2 (min -1 ) 1.2 1.0 0.8 0.6 0.
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I (arb. unit) 140 120 100 80 60 40
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I (arb. unit) 5 4 3 2 1 0 0.000 0.0
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I > (arb.unit) 1.0 0.9 0.8 0.7 0.6
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shown in Fig. 4.14. It can be seen
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I is (mA) 0.25 0.20 0.15 0.10 0.05
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value. When ton has been kept const
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survival curve characteristics were
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of the effects produced by differen
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solutely necessary for a profound u
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Conferences 1. Bacillus spores ster
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[9] W. A. Rutala, D. J. Weber, J. H
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[34] J. H. Young: Sterilization wit
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[57] M. K. Boudam, M. Moisan, B. Sa
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[79] J. Schneider, K. M. Baumgartne
Page 127 and 128:
[100] S. Villeger, S. Cousty, A. Ri
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