Giseok Kang

Discrimination between the human prostate normal cell and cancer cell by using a novel electrical impedance spectroscopy controlling the cross-sectional area of a microfluidic channel

The prostate biopsy method shows a high false negative result because the suspicious tissue considered as cancer is not confirmed during tissue sampling. Thus, repeated biopsy procedures and diagnostic errors in relation to prostate cancer frequently occur. The purpose of this research is to enhance the prostate cancer detection rate by using microfluidic electrical impedance spectroscopy (μEIS), which allows real-time measurement of the electrical impedance of a single human prostate normal cell and cancer cell. The μEIS was equipped with a movable flexible membrane, which is operated by pneumatic pressure to capture the single cell on the surface of sensing electrodes. The forced tight contact between the cell and electrodes makes it possible to measure the electrical characteristics of the cell with a high sensitivity. The μEIS discriminates well between normal human prostate cells (RWPE-1) and cancer cells (PC-3) at 8.7 kHz based on the electrical signal responses of the cells. The average difference rates of admittance magnitude and susceptance are 54.55% and 54.59%, respectively. The developed μEIS also shows high repeatability, which was verified by a deionized water test conducted before and after each cell assay; the maximum variance of both the impedance and admittance at 8.7 kHz was as small as 9.48%.

Differentiation Between Normal and Cancerous Cells at the Single Cell Level Using 3-D Electrode Electrical Impedance Spectroscopy

A novel microdevice for electrical impedance spectroscopy is presented to differentiate between normal and cancerous cells at the single cell level with a high sensitivity. The device utilizes a microfluidic tunnel structure, whose height is smaller than the cell diameters, to squeeze the target cells. Thus, the tight contact between the cells and electrodes allows the device to measure the intrinsic electrical properties of the cells with a higher sensitivity than through noncontact methods. Three-dimensional interdigitated electrodes (3-D IDE) are also employed to confine most of the electric field into the cell membrane, which contains the meaningful electrical properties. Consequently, the variance of the measured values could be reduced because the position of target cells is almost the same in every cell assay. The device well distinguishes normal human breast cells (MCF-10A) from early-stage human breast cancer cells (MCF-7) by means of electrical impedances at 500 kHz; the average differences of the real part and phase angle between the target cells are 44.4 and 1.41 , respectively. The proposed device also shows a high repeatability for the deionized (DI) water test conducted before and after each cell assay; the variances of the real part and phase angle of electrical impedance at 500 kHz are as small as 9.07 and 0.27 , respectively.

Impedance measurement of normal and cancerous human breast cells using a microfluidic tunnel

In this paper, a novel microelectrical impedance spectroscopy (μEIS) with three-dimensional interdigitated electrodes (3D-IDE) is developed to differentiate normal and cancerous cells. The device utilizes a microfluidic tunnel structure, which forces cells to be squeezed. Thus, the enlarged contact area between cells and electrodes allows the device to measure the intrinsic electrical signal of the cells with a higher sensitivity than a noncontact case. The cell squeezing is realized by fabricating smaller microfluidic channel than cell size. The electrical impedances are measured through 3D-IDE. The device well distinguishes normal human breast cell (MCF-10A) and early-stage human breast cancer cell (MCF-7) with a phase difference of 1.42° at 500 kHz. The proposed device also features a high repeatability because the phase change is as small as 0.27° (which is sufficiently smaller than the phase difference between normal and cancer cell) before and after the each cell assay.

Cell Electrical Impedance as a Novel Approach for Studies on Senescence Not Based on Biomarkers.

Senescence of cardiac myocytes is frequently associated with heart diseases. To analyze senescence in cardiac myocytes, a number of biomarkers have been isolated. However, due to the complex nature of senescence, multiple markers are required for a single assay to accurately depict complex physiological changes associated with senescence. In single cells, changes in both cytoplasm and cell membrane during senescence can affect the changes in electrical impedance. Based on this phenomenon, we developed MEDoS, a novel microelectrochemical impedance spectroscopy for diagnosis of senescence, which allows us to precisely measure quantitative changes in electrical properties of aging cells. Using cardiac myocytes isolated from 3-, 6-, and 18-month-old isogenic zebrafish, we examined the efficacy of MEDoS and showed that MEDoS can identify discernible changes in electrical impedance. Taken together, our data demonstrated that electrical impedance in cells at different ages is distinct with quantitative values; these results were comparable with previously reported ones. Therefore, we propose that MEDoS be used as a new biomarker-independent methodology to obtain quantitative data on the biological senescence status of individual cells.

Development of Electro-thermal Acupunctures for Physical Therapy of Ligament

The thermal acupuncture is used to heal the ligament injury. Conventional thermal acupunctures have side effects such as skin burn and inefficiency in terms of curative effect. In order to overcome the shortcomings of the previous acupunctures, we develop a novel electro-thermal acupuncture using micro-electromechanical systems (MEMS) technology, which could be an approach to treat ligament injuries and maximize curative effect by localized heat generation. Moreover, the developed acupuncture is realized based on the conventional acupuncture without giving unfamiliar sensations to patients. It is essential to successfully pattern metal electrodes on the curved surface of conventional acupunctures in order to produce the electro-thermal acupuncture for therapeutic purpose. The problem related to patterning on the curved surface was resolved by means of a flexible photomask made of Parylene C film. We demonstrate the metal patterning technique with high resolution that is less than 5% dimensional error on the acupuncture. The proposed new acupuncture includes electrical impedance sensor (EIS) and micro-heater to detect a desired target area and stimulate intensively in a very focused region. With the developed acupuncture, we expect it to be used for ligament treatment accurately and effectively.