Chang-Ju Park

Microelectrical Impedance Spectroscopy for the Differentiation between Normal and Cancerous Human Urothelial Cell Lines: Real-Time Electrical Impedance Measurement at an Optimal Frequency.

Purpose. To distinguish between normal (SV-HUC-1) and cancerous (TCCSUP) human urothelial cell lines using microelectrical impedance spectroscopy (μEIS). Materials and Methods. Two types of μEIS devices were designed and used in combination to measure the impedance of SV-HUC-1 and TCCSUP cells flowing through the channels of the devices. The first device (μEIS-OF) was designed to determine the optimal frequency at which the impedance of two cell lines is most distinguishable. The μEIS-OF trapped the flowing cells and measured their impedance at a frequency ranging from 5 kHz to 1 MHz. The second device (μEIS-RT) was designed for real-time impedance measurement of the cells at the optimal frequency. The impedance was measured instantaneously as the cells passed the sensing electrodes of μEIS-RT. Results. The optimal frequency, which maximized the average difference of the amplitude and phase angle between the two cell lines (p < 0.001), was determined to be 119 kHz. The real-time impedance of the cell lines was measured at 119 kHz; the two cell lines differed significantly in terms of amplitude and phase angle (p < 0.001). Conclusion. The μEIS-RT can discriminate SV-HUC-1 and TCCSUP cells by measuring the impedance at the optimal frequency determined by the μEIS-OF.

Hard polymer cladding fiber (HPCF) links for high-speed short reach 1/spl times/4 passive optical network (PON) based on all-HPCF compatible fused taper power splitter

We report a novel 4/spl times/4 hard polymer clad fiber (HPCF) splitter fabricated by a fusion and tapering technique showing an excess loss less than 4.58 dB and insertion loss of 10.50 dB, which can be directly applied in short reach (SR) HPCF optical links. The device also showed an excellent uniformity in the power splitting ratio with power fluctuation less than 0.25 dB over a wide spectral range, 600-900 nm, which can significantly alleviate the spectral requirements in transmitters and enable wavelength-division multiplexing. The 1/spl times/4 passive optical network SR HPCF link for Ethernet communication was experimentally demonstrated over 100 m of HPCF at the data rate of 1.25 Gb/s for the optical signal at 850 nm.

Anti-Reflux Ureteral Stent with Polymeric Flap Valve Using Three-Dimensional Printing: An In Vitro Study.

PURPOSE This article aims to describe the design of an anti-reflux ureteral stent with a polymeric flap valve and the fabrication methods using three-dimensional (3D) printing. The stent effectively prevents backward flow with a negligible reduction in forward flow. Fabrication of miniaturized valves was easy with high precision and rapid prototyping. MATERIALS AND METHODS The proposed stent comprised a 7F Double-J (DJ) stent and a polymeric flap valve. The valve was made of Tango Plus FLX980 and was fabricated using a 3D printer. Two types of stent were prepared for in vitro tests: DJ stents with (1) an uncoated valve (UCV) stent and (2) a parylene C coated valve (PCV) stent for enhanced biocompatibility. The flow characteristics of each stent were evaluated considering flow direction, parylene coating, and stent side holes, and were compared to the intact DJ stent. RESULTS The forward flow rate for the distal portion of the UCV and PCV stents was 9.8 mL/min and 7.8 mL/min at applied pressure of 15 cm H2O (normal anterograde pressure in patients with stents), respectively. Backward flow rate for the distal portion of the UCV and PCV stents was decreased by 28 times and 8 times at applied pressure of 50 cm H2O (maximum bladder pressure), respectively, compared with the distal portion of the intact DJ stent. Forward flow rates of whole stents were 22.2 mL/min (UCV stent) and 20.0 mL/min (PCV stent) at applied pressure of 15 cm H2O, and backward flow rates of whole UCV and PCV stents were decreased by 8.3 times and 4.0 times at applied pressure of 50 cm H2O, respectively, compared with the intact DJ stent. CONCLUSIONS The anti-reflux ureteral stent was successfully designed and fabricated using a 3D printer. In vitro studies showed that the stent effectively prevented backward flow while minimizing reduction in forward flow.

Ex vivo characterization of age-associated impedance changes of single vascular endothelial cells using micro electrical impedance spectroscopy with a cell trap

We aimed to characterize aging of single vascular endothelial cells, which are indicators of senescence, using micro electrical impedance spectroscopy (μEIS) for the first time. The proposed μEIS was equipped with two barriers under the membrane actuator near the sensing electrodes, increasing its cell-trapping capability and minimizing the interference between the target cell and subsequent cells. The cell-trapping capability in μEIS with barriers was considerably improved (90%) with a capture time of 5 s or less, compared to μEIS without barriers (30%). Cells were extracted from transgenic zebrafish to minimize an initial discrepancy originating from genetic differences. In order to estimate useful parameters, cytoplasm resistance and membrane capacitance were estimated by fitting an electrical equivalent circuit to the data of ex vivo sensor output. The estimated cytoplasm resistance and membrane capacitance in the younger vascular endothelial cells were 20.16 ± 0.79 kΩ and 17.46 ± 0.76 pF, respectively, whereas those in the older cells were 17.81 ± 0.98 kΩ and 20.08 ± 1.38 pF, respectively. Discrimination of each group with different aging showed statistical significance in terms of cytoplasm resistance (p < 0.001) and membrane capacitance (p < 0.001). Considering both of the sensor and cellular level, the optimal frequency was determined as 1 MHz at which the electrical impedance of each group was clearly discriminated (p < 0.001).

LBPS 01-14 MICRO-ELECTROCHEMICAL IMPEDANCE SPECTROSCOPY WITH A PRESSURE-DEPENDENT MEMBRANE ACTUATOR FOR CHARACTERIZING AGE-RELATED CHANGES IN SINGLE VASCULAR ENDOTHELIAL CELL

Objective: Directly detect age-related changes in electrical impedance of single vascular endothelial cell without using biomarkers. Design and Method: Aging is one of the major factors in cardiovascular disease (CVD). However, it is difficult to differentiate changes in cardiovascular system between the aged and the diseased. If the difference could be characterized clearly, it would be potential help to understand pathophysiology. In this study, micro-electrochemical impedance spectroscopy (&mgr;EIS) with a pressure-dependent membrane actuator for cell-capturing was used to characterize age-related changes in electrical impedance of sorted single vascular endothelial cell from dissected hearts of transgenic zebrafish (fli1a:EGFP). The electrical impedance for each group (3, 4, and 18-month-old) was measured 30 times from 1 kHz to 1 MHz under 250, 300, and 350 kPa of capturing pressures, respectively. Results: Maximum differences in the average electrical impedance among the three cell groups were observed at 1 MHz, and these differences were statistically significant for all capturing pressures (p < 0.05, one-way ANOVA). Figure 1 shows the changes in the electrical impedance depending on different ages at different capturing pressure. Our results show that both electrical parameters (resistance and reactance) similarly change with aging for all capturing pressures. The resistance increased monotonously with aging, whereas the reactance decreased in 4-month-old and then increased in 18-month-old cells. Especially, 350kPa of capturing pressure could clearly discriminate electrical impedance of different aging groups. Conclusions: We applied &mgr;EIS to zebrafish vascular endothelial cells at different ages and found that resistance increased monotonously with aging, while reactance decreased during early ages and increased in aged cells. Age-related changes in resistance and reactance can be attributed to the changes in fluidity and permeability of cells due to metabolic remnants such as hydrogen ion and reactive oxygen species. In this context, the proposed &mgr;EIS could be considered as a potential diagnostic tool for CVD to detect age-related changes.

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.