Download Cell Membrane for Biologic Cells

Journal of Information Technology and Applications
Vol. 7, No. 2, pp. 30-33 2013
Cell Membrane of Biologic Cells for Gate Dielectric Application
I. J. Hsieh
Department of Electrical Engineering, Chung-Hua University,
Hsinchu, Taiwan, R.O.C.
E-mail: [email protected]
Abstract
In the future, according to the continuous scaling down of device, the thickness of gate oxide has to be
reduced. The thickness of gate oxide will be decreased to the limitation. It has been investigated into the
feasibility of the biological cell, in order to substitute for the gate dielectric. Then it is experimented with the
relationship between the cell and the electric field.
Keywords: gate oxide, biological cell, and dielectric
* Corresponding author.
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Journal of Information Technology and Applications
Vol. 7, No. 2, pp. 30-33 2013
1. Introduction
The CMOS technology is being continuously scaled
towards smaller dimensions region due to the
increasing need for higher speed, integration density, as
well as lower power consumption applications [1-2].
The continuous scaling down of device, the thickness of
gate oxide has to be reduced. The thickness of gate
oxide will be decreased to the limitation. It is the
purpose to investigate the feasibility of the biological
cell, in order to substitute for the gate dielectric in this
paper.
The penetration of cell membrane is important for
the cloning of Dolly sheep. One role played by the
electric field used in cloning is to cause recoverable
transient breakdown of cell membrane for both donor
and recipient cells. However, there is only little
understanding of cell membrane integrity dependence
on electric field as shown in Fig.1 [3]. In addition, it is
wondering if it is possible to control the transient
breakdown in multi- parallel, which is important for
certain applications like bio-computers. For these
purposes, we have integrated the human placenta TL
and lung cancer cell A549 into 3D trap arrays on Si
substrate and studied the electrically stimulated cell
membrane breakdown phenomenon. The applied
electric field can break down the cell membrane and
destroy the cell. The dependence of cell membrane
breakdown distributions on electric field have been
measured. From measured data, the survival rate of
cells under the electric field stress is similar to the gate
dielectric reliability of MOSFET as shown in Fig.2 [4].
Fig.2 The Cell membrane is similar to the gate
dielectric in the MOSFET.
2. Experiments
KOH was used to etch the 4-in Si wafer to a
designed deep trench array structure after depositing
300 nm Si3N4 for masking. The average depth of the
trench was 50 m , which was deep enough for locating
and fixing the cells. Then a 200 nm SiO2 was grown for
electrically isolating the low-resistivity Si substrate.
Depositing 2 m thick aluminum layer and subsequent
patterning fabricated the electrode. The human placenta
TL and lung cancer cell A549 were directly cultured on
the fabricated 3D traps by immerging the Si chip into
the culture medium. The cell membrane breakdown was
studied by applying voltage to the electrode pad of 3D
traps. The survival rate was calculated by counting the
Trypan blue stained cells, since the cell membrane was
already broken under the applied electric field to allow
the blue dye to diffuse into the cells.
3. Results and Discussions
Since the cell membrane was made of lipids and
proteins with relatively poor electrical conductivity as
shown in Fig.3. It can be treated as a dielectric layer
similar to gate dielectric used in Si MOSFET. Fig.4
shows the fabricated 3D trap arrays and metal lines on
Si substrate for cell culture. Fig.5 reveals the current
flowing through the cells under applied voltage. The
cell membrane behaves like an insulator layer when the
voltage is smaller than 3 V, since only small current
was flowing through the cells and closed to dummy
culture medium. However, the current density increased
linearly with increasing voltage, as the voltage is larger
than 5 V, indicating that some cell membranes were
broken to release ions from cytoplasm and nucleus.
Fig.1 The principle of the cell membrane is integrity
dependence on the electric field.
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Journal of Information Technology and Applications
Vol. 7, No. 2, pp. 30-33 2013
(a)
(b)
(c)
Fig.3 (a) The TEM picture of a human placenta cell, (b) the structure of a MOSFET, and (c) the TEM picture of the
gate dielectric in the MOSFET.
by using Trypan Blue stain, which stained the cell
cytoplasm if there were leaks on the cell membrane.
Fig.6 (a) and (b) show the comparison of human
placenta TL cells before and after applied voltage,
respectively, where the dyes only stain the cells if the
membrane was damaged by electric field.
Fig.4 The picture of the fabricated 3-D cell traps on Si
with electrical electrode patterns. The trench is for
allocating and restraining the cells.
(a)
(b)
Fig.6 The pictures of the human placenta TL cells (a)
before and (b) after Electric field applying, and stained
by Typan Blue is applied to both case but only stains
the cells after applying voltage because of the leaks on
the cell membranes.
By counting the number of the stained cells (broken
cell membrane) and unstained cells, we analyzed the
relationship between the applied electric field and the
survival rate of the cells. Fig.7 shows the survival rate
of human placenta cells after 20 sec electric stress. The
survival rate started to decrease abruptly after
increasing electric field > 40 V/cm and reached <4 % at
80 V/cm. The measured reducing survival rate trend of
human placenta cells with increasing electric field was
consistent with those of human lung cell A549 shown
in Fig.8 shows the survival rate vs. distance between
two electrodes for human lung cancer cell A549 after
applied 0 ~ 20 V linearly sweep voltage. The survival
rate reached a higher value of 97 % at the distance of
3000 μm but reduced to 74 % at 1000μm, which
suggests that the electric field breakdown the cell
membranes are similar to that of the gate dielectric in
MOSFET.
Fig.5 The current density flowing through the cells with
the applied voltage. Some cell membrane started to
breakdown and broken at above 4V. The dummy
cultivation liquid keeps very low conductivity over the
whole voltage range.
At higher electric field, the cell membranes were
completely broken and the nucleus was exposed as
analyzed by transmission electric microscope (TEM).
The status of the cell membrane could be investigated
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Journal of Information Technology and Applications
Vol. 7, No. 2, pp. 30-33 2013
[4]
Fig.7 The survival rate of the human placental TL cells
with the applied electric field. The survival rate reduces
from ~100 % to < 4 % after 40 V/cm.
Fig.8 The survival rate of the human lung cancer cells
with the applied electric field. The reduction trend with
increasing electric field is similar to that of the human
placenta TL cells shown in Fig.6.
4. Conclusions
The integration of cells into 3D trenched trap arrays
in Si substrate and the electrical control of the cell
membranes integrity are important for future biomedical applications. In order to substitute for the gate
dielectric, the stability of the biological cell has been
investigated.
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