Sachiko Iseki

Selective killing of ovarian cancer cells through induction of apoptosis by nonequilibrium atmospheric pressure plasma

Two independent ovarian cancer cell lines and fibroblast controls were treated with nonequilibrium atmospheric pressure plasma (NEAPP). Most ovarian cancer cells were detached from the culture dish by continuous plasma treatment to a single spot on the dish. Next, the plasma source was applied over the whole dish using a robot arm. In vitro cell proliferation assays showed that plasma treatments significantly decreased proliferation rates of ovarian cancer cells compared to fibroblast cells. Flow cytometry and western blot analysis showed that plasma treatment of ovarian cancer cells induced apoptosis. NEAPP could be a promising tool for therapy for ovarian cancers.

Rapid inactivation of Penicillium digitatum spores using high-density nonequilibrium atmospheric pressure plasma.

A promising, environmentally safe method for inactivating fungal spores of Penicillium digitatum, a difficult-to-inactivate food spoilage microorganism, was developed using a high-density nonequilibrium atmospheric pressure plasma (NEAPP). The NEAPP employing Ar gas had a high electron density on the order of 10(15) cm(-3). The spores were successfully and rapidly inactivated using the NEAPP, with a decimal reduction time in spores (D value) of 1.7 min. The contributions of ozone and UV radiation on the inactivation of the spores were evaluated and concluded to be not dominant, which was fundamentally different from the conventional sterilizations.

Inactivation of Penicillium digitatum Spores by a High-Density Ground-State Atomic Oxygen-Radical Source Employing an Atmospheric-Pressure Plasma

Penicillium digitatum spores were inactivated using an oxygen-radical source that supplies only neutral oxygen radicals. Vacuum ultraviolet absorption spectroscopy was used to measure the ground-state atomic oxygen [O (3Pj)] densities and they were estimated to be in the range of 1014–1015 cm-3. The inactivation rate of P. digitatum spores was correlated with the O (3Pj) density. The result indicates that O (3Pj) is the dominant species in the inactivation. The inactivation rate constant of P. digitatum spores by O (3Pj) was estimated to be on the order of 10-17 cm3 s-1 from the measured O (3Pj) densities and inactivation rates.

Real-time in situ electron spin resonance measurements on fungal spores of Penicillium digitatum during exposure of oxygen plasmas

We report the kinetic analysis of free radicals on fungal spores of Penicillium digitatum interacted with atomic oxygen generated plasma electric discharge using real time in situ electron spin resonance (ESR) measurements. We have obtained information that the ESR signal from the spores was observed and preliminarily assignable to semiquinone radical with a g-value of around 2.004 and a line width of approximately 5G. The decay of the signal is possibly linked to the inactivation of the fungal spore. The real-time in situ ESR has proven to be a useful method to elucidate plasma-induced surface reactions on biological specimens.

Electron spin resonance (ESR) study of radicals on biological organism created by interaction with plasma

Summary form only given. For bio-applications of atmospheric pressure plasmas, our group has been reported previously that inactivation of microorganisms such as fungal spores of Penicillium digitatum by employing high-density non-equilibrium atmos pheric pressure plasma [1]. To understand a mechanism of inactivation, there needs analysis of reactions between plasmas and biomaterials. It has long been appreciated that radicals play important roles for controlling the reactions. The electron-spin-resonance (ESR) technique can detect the radicals - in particular dangling bonds - and thus we have developed methods to utilize the ESR for this purpose [2]. In this study, we focused on ESR detection of radical on biologi cal organism as exampled of the Penicillium digitatum interacted with plasmas.

Inactivation mechanism of Penicillium digitatum using atmospheric pressure plasma

We discussed the inactivation mechanism of Penicillium digitatum treated by nonequiribrium atmospheric pressure plasma. We focused on the ozone, ultraviolet radiation, O radical, and OH radical as inactivation factor. The diagnostics of non-equilibrium atmospheric pressure plasma was performed by optical emission spectroscopy and ultraviolet absorption spectroscopy. It is confirmed that the effects of ozone and ultraviolet radiation were not dominant for the inactivation of P. digitatum. Results from experiments on the O2 gas and water vapor addition showed that the contribution of the reactive oxygen species such as OH radical, O radical and their byproduct would be larger.