S-O3-7
Plasma Biosciences Research Center for Next Generation Green and Life
Science and Technology
Eun Ha Choi, N. Kaushik, H. S. Uhm, G. S. Park
Department of Electrophysics& Plasma Bioscience
Plasma Bioscience Research Center, Kwangwoon University, Seoul 139-701, Korea
Email: ehchoi@kw.ac.kr
The Plasma Bioscience Research Center (PBRC) has been based on the plasma sciences, chemistry,electronics and biomedicines, which include creative research elements and purposes. Basic researches on
the characteristic of the bioplasma sources applicable to the living cell, especially to the human body willbe investigated, along with the fundamental researches of mutual interactions between the bioplasma andorganic-inorganic, liquid materials. Also the general introduction for PBRC will be briefly introduced formutual networkings and cooperations for human health care of cancer therapy and bacteria killings. We
have investigated the nonthermal bioplasma sources and their interactions with microbial, fungi, yeast andliving cells. Herein, we have investigated the basic interactions of nonthermal dielectric-barrier discharge
plasma with the Escherichia coli in morphologicl and biomolecular aspects under lethal dose. This work
will contribute to the understanding of the exact biological pathways of plasma interaction with livingorganisms.

1. Introduction

2. Experimentals

Over the past several years, many plasma jet anddielectric barrier discharge (DBD) devices that
produce a cold atmospheric-pressure plasma plume
have been investigated for their use for thermallysensitive materials and medical applications. We
have used the micro-discharges in the porousalumina, from which a plasma jet has been ejectedfrom the outer electrode through a 1 mm hole,showing that the temperature of the jet decreases toa value close to the room temperature. This device
is capable of generating a soft plasma whoseplasma potential is almost zero and plume length isin several centimeters. It exhibits low power
requirements (0.5~5W) as shown by its current
voltage characteristics. Soft plasmas offer attractive
opportunities since non-thermal plasmas can supply
chemically active species without heating and/or
damaging the materials to be processed. This
non-thermal atmospheric pressure soft plasma cangenerate the various kinds of radicals which can beimportant roles for the plasma interactions withmicrobial living cells. It is therefore, important toinvestigate the influence of plasma jet and DBD
plasma on the Saccaromyces Cerevisie (yeast),
Escherichia Coli and T98G human brain cancer celllines. Also the energy band structure of thesebiological cells from results of secondary electron
emission coefficient (γ) by gamma focused-ion
beam (γ-FIB) system. Here the work-function(φ(w)), energy band width χ, center energy ofthe valence band ε0 and any other important
information of these biological cells are also
accordingly analyzed.

In this experiment, we have prepared three kindsof samples yeast, E.coli and cancer cell. We have
exposed plasma to each samples. For the yeast, it
has been exposed to atmospheric Ar soft plasma jetwith 4 kV, 13 mA, and 22 kHz in frequency by 1min. Yeast cells seeded in 200µl of water have beenplaced in each well of microtiter plate. And theatmospheric N2 soft plasma jet has been exposed tothe E.coli for 5min. The discharge gap for the soft
plasma is adjusted to 2 mm between the inner andouter electrode. Gas is injected into the injectionneedle and is then ejected through the 1 mm hole in
the outer electrode via the porous alumina, whose
pore diameter is 100 µm. Also the dielectric barrierdischarge (DBD) plasma has been exposed to thecancer cell by 4 min in this experiment. This DBD
plasma treatment system consists of a high-voltage
power supply, electrodes, and dielectrics. The upper
electrode is made of ITO paste electrode and lower
electrode facing the sample is made of stainlesssteel mesh. The output power was about 17 W (2.2kV & 11 mA with phase angle of 0.7 radians).
For observing the change in energy band
structure of the biological materials, secondary
electron emission coefficient (γ) has been measured
by gamma focused-ion beam (γ-FIB) system[1,2].
Here the work-function (φ(w)),
energy band
width χ, center energy of the valence band ε0 andany other important information of biologicalmaterials are also accordingly analyzed by using theslow ions of He+[2] with energy less than 200eV.
The energy band structure fe(α) function in valenceband can be measured from the electron energy
distribution of the secondary electrons throughout
the Fast Fourier Transform (FFT) and inverse-Fast
Fourier Transform.
3. Results and Discussions
Plasma exposure to yeast has caused
dramatic changes in cell morphology. After
treatment with plasma for 1 min., majority ofyeast cells appears to be shrunken as in Fig.
1(a). The smooth surfaces for control cells (noplasma treated) of E. Coli has been changed torough and crushed surfaces after plasma
treatment as in Fig. 1(b). Also it has been noted(a)(b)(c)
Fig. 1. SEM images of each sample for yeast (a),E. Coli (b) , and cancer cells (c); (a) and (b) aretreated by Ar and N2 soft plasma jet,respectively, while (c) is by DBD plasma.

that cancer cell shrinkage and cell killing by
DBD plasma treatment have been observed asshown in Fig. 2(c), which are also reported byother many groups [3].

Fig. 2. Growth kinetics of T98G cells at 2 and48 hours after treatment by DBD plasma.
Figure 2 shows the growth kinetics of T98Gcells. Cells proliferation kinetics have beenstudied at 24, 48, 72 hours after plasma
treatment,
following
trypsinization
andcounting total cells per plate by using a trypan
blue dye and hemocytometer. This growth
kinetics assay showed that our plasma haveinhibitory effect on the growth of T98G cells inexposure and incubation time dependent
manners. Maximum effect is shown by 240

seconds plasma exposure; it inhibits the growthof cells up to 80% at 48 and 72 hours after
treatment and its viability range is 19-20%.
We have also measured the electron energy
band structure for each biological material invalence band by γ-FIB. We can measurework-function (φ(w)), center energy of thevalence band (ε0) and energy band structure
function fe(x) in each samples by taking theinverse-Fast Fourier Transform (IFFT) to
Auger transform function T(Ek), which is
identical
tothesecondary
electron’sdistribution function. For the E.coli, it is foundthat the work-function (φ(w)) is is (7.79 eV, 7.49eV) for the (before, after) the plasma treatment,
respectively.
Since the yeast, E. Coli, and cancer cells are
immersed in water during plasma treatment inthis experiment, it is likely that plasma hasaltered the pH properties of water media andthis eventually affects the cell surface
morphology, which results in the electronenergy distribution in the valence band ofthese surface structures[4].

4. Conclusion
The electron energy band structure for the
microbial and living cells has been changed byplasma treatment, in which both the work function
and central energy of the valence band areaccordingly decreased toward the their surface.
Acknowledgments

The authors would like to gratefully
acknowledge financial support by the SRC programof National Research Foundation of Korea(20100029418) in 2011.
References[1] J. Y. Lim, J. S. Oh, B. D. Ko, J. W. Cho, S. O. Kang,G. Cho, E. H. Choi, Applied Phys. Lett. 94 (2003) p.768.
[2] H. S. Uhm, Y. H. Hong, E. H. Choi, and D. Kim,Appl. Phys. Lett. 98 (2011) 061501.
[3] Z. Xiong, X. P. Lu, A. Feng, Y. Pan and K. Ostrikov,Physics of Plasmas 17 (2010) 123502.
[4] Y. H. Kim, G. Y. Baik, E. H. Choi, Accepted in J.
Korean Phys. Soc. Nov. (2011).