We report the results of an interdisciplinary collaboration formed to assess the sterilizing capabilities of the One Atmosphere Uniform Glow Discharge Plasma (OAUGDP). This newly-invented source of glow discharge plasma (the fourth state of matter) is capable of operating at atmospheric pressure in air and other gases, and of providing antimicrobial active species to surfaces and workpieces at room temperature as judged by viable plate counts. OAUGDP exposures have reduced log numbers of bacteria, Staphylococcus aureus and Escherichia coli, and endospores from Bacillus stearothermophilus and Bacillus subtilis on seeded solid surfaces, fabrics, filter paper, and powdered culture media at room temperature. Initial experimental data showed a two-log10 CFU reduction of bacteria when 2 x 10(2) cells were seeded on filter paper. Results showed > or = 3 log10 CFU reduction when polypropylene samples seeded with E. coli (5 x 10(4)) were exposed, while a 30 s exposure time was required for similar killing with S. aureus-seeded polypropylene samples. The exposure times required to effect > or = 6 log10 CFU reduction of E. coli and S. aureus on polypropylene samples were no longer than 30 s. Experiments with seeded samples in sealed commercial sterilization bags showed little or no differences in exposure times compared to unwrapped samples. Plasma exposure times of less than 5 min generated > or = 5 log10 CFU reduction of commercially prepared Bacillus subtilis spores (1 x 10(5)); 7 min OAUGDP exposures were required to generate a > or = 3 log10 CFU reduction for Bacillus stearothermophilus spores. For all microorganisms tested, a biphasic curve was generated when the number of survivors vs time was plotted in dose-response cures. Several proposed mechanisms of killing at room temperature by the OAUGDP are discussed.

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The medical, industrial, and food processing industries are constantly in search of new technologies to provide improved methods of sterilization and pasteurization. Proposed techniques must deal with such problems as thermal sensitivity and destruction by heat, formation of toxic by-products, cost, and inefficiency in performance. We report results from a newly invented plasma source, a one atmosphere uniform glow discharge plasma (OAUGDP), which is capable of operating at atmospheric pressure in air and providing antimicrobial active species at room temperature. OAUGDP exposures have reduced log numbers of bacteria (Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa), bacterial endospores (Bacillus subtilis and Bacillus pumilus), and various yeast and bacterial viruses on a variety of surfaces. These surfaces included polypropylene, filter paper, paper strips, solid culture media, and glass. Experimental results showed at least a ⩾5 log10 colony forming units (CFU) reduction in bacteria within a range of 15–90 s of exposure, whether the samples were exposed in conventional sterilization bags or exposed directly to the plasma. An exception to these very short exposure times were experiments with solid culture media in which 5 min of plasma exposure was necessary to produce ⩾5 log10 CFU reduction in bacterial counts. The effects of plasma treatment on bacterial cell structures were investigated by exposing cells to plasma for various durations and examining them by transmission electron microscopy. The results showed that cell breakage (lysis) occurred with the release of cellular contents. These data were consistent with spectrophotometric results in which the release of cellular constituents was measured as a change in ultraviolet absorption at 260 nm. With all microorganisms tested, a biphasic survival curve (logarithmic number of survivors versus time) was observed in plots of dose-response data. Differences in susceptibilities of microorganisms observed on various surfaces suggested that the degree of lethality was dependent upon the time of diffusion of active species through the medium to the organism and the makeup of the microbial cellular surface.

K n m i U e , TN37996This paper reviews recent studies on the mechanism of corona treatment of polyolefin fi.lms, specifically the chemical and physical changes of this process and the self-adhesion mechanism. Corona discharge of polymeric films introduces polar groups into the surfaces, which increases the surface energy and, as a consequence, improves substrate wettability and adhesion. The main chemical mechanism of corona treatment is oxidation. In addition, corona treatment can crosslink surface regions and increase the film cohesive strength.

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