a b s t r a c tCold atmospheric plasma treatment of microorganisms and living tissues has become a popular topic in modern plasma physics and in medical science. The plasma is capable of bacterial inactivation and noninflammatory tissue modification, which makes it an attractive tool for treatment of skin diseases, open injuries and dental caries. Because of their enhanced plasma chemistry, Dielectric Barrier Discharges (DBDs) have been widely investigated for some emerging applications such as biological and chemical decontamination of media at ambient conditions. Despite the high breakdown voltage in air at atmospheric pressure, the average current of DBD discharges is low. Therefore, a DBD can be applied in direct contact with biological objects without causing any damage. In this work a 60 Hz DBD reactor, which generates cold atmospheric plasma inside Petri dishes with bacterial culture, is investigated. Samples of Staphylococcus aureus, a Gram-positive bacterium and Escherichia coli a Gram-negative bacterium were selected for this study. The bacterial suspensions were evenly spread on agar media planted in Petri dishes. The reactor electrodes were placed outside the Petri dish, thus eliminating the risk of samples microbial contamination. The covered Petri dish with agar medium in it serves as dielectric barrier during the treatment. The plasma processing was conducted at same discharge power (∼ 1.0 W) with different exposure time. Sterilization of E. coli and S. aureus was achieved for less than 20 min. Plasma induced structural damages of bacteria were investigated by Scanning Electron Microscopy.

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The response of a biological environment when in contact with an artificial material is primarily determined by the material surface properties such as composition, contact angle and free surface energy [1,2]. Owing to that, different treatments have been employed to improve the performance of biocompatible materials. In this sense, plasma-based techniques are very attractive because they enable the surface processing of materials with virtually any geometry preserving bulk properties. Furthermore, other characteristics make plasma treatment of particular interest in biomaterial processing. Those characteristics include, for instance, a) the possibility of using a large number of different chemicals to introduce any desired functional group on the surface, b) the treatment is performed in an intrinsically sterile environment and, c) different kind of materials (such as ceramics, metals and polymers) including those chemically inert can be treated.

Thermal and optical properties of two different nanofluids containing SiO 2 and TiO 2 semiconductor nanoparticles were studied by thermal lens spectrometry (TLS) and spectrophotometry. In the case of SiO 2 nanofluids the transmission electron microscopy technique was used to obtain the SiO 2 nanoparticle sizes to investigate the size effect of these nanoparticles on the sample thermal diffusivity which is important in some medical applications such as photothermal-modulated drug delivery systems. On the other hand for the case of TiO 2 nanofluids, the photopyroelectric technique, TLS, scanning electron microscopy, and X-ray diffraction were employed to investigate the concentration effect on the thermal properties of these nanofluids. Thermal diffusivities and effusivities as functions of the TiO 2 nanoparticle concentrations were obtained. From the experimental results, an incremental increase in the thermal diffusivities and effusivities was observed when the nanoparticle concentration was increased, indicating that the nanoparticle concentration is an important factor to be considered to obtain nanofluids with more thermal efficiency which are required for some applications, such as degradation of residual water.