Dong-Keun Jung

Anti‐apoptotic role of phospholipase D in spontaneous and delayed apoptosis of human neutrophils

Neutrophil apoptosis is a constitutive process that can be enhanced or delayed by signals induced by various stimuli. We investigated the role of phospholipase D (PLD) in neutrophil apoptosis. The apoptotic rate of neutrophils was found to be increased by 1‐butanol and decreased by the exogenous addition of PLD. Moreover, the delay of apoptosis by apoptosis‐delaying stimuli such as granulocyte/macrophage colony‐stimulating factor or lipopolysaccharide (LPS) was also blocked by 1‐butanol. Unstimulated PLD activity in cultured cells for 20 h was higher than that in freshly isolated cells and further increased in cultured cells with LPS. These results suggest that PLD is involved in the up‐regulation of neutrophil survival.

A disposable amperometric dual-sensor for the detection of hemoglobin and glycated hemoglobin in a finger prick blood sample

A disposable microfluidic amperometric dual-sensor was developed for the detection of glycated hemoglobin (HbA1C) and total hemoglobin (Hb), separately, in a finger prick blood sample. The accurate level of total Hb was determined through the measurements of the cathodic currents of total Hb catalyzed by a toluidine blue O (TBO)-modified working electrode. Subsequently, after washing unbound Hb in the fluidic channel of dual sensor with PBS, the cathodic current by only HbA1C captured on aptamer was monitored using another aptamer/TBO-modified working electrode in the channel. To modify the sensor probe, poly(2,2´:5´,5″-terthiophene-3´-p-benzoic acid) and a multi-wall carbon nanotube (MWCNT) composite layer (pTBA@MWCNT) was electropolymerized on a screen printed carbon electrode (SPCE), followed by immobilization of TBO for the total Hb probe and aptamer/TBO for the HbA1C probe, respectively. The characterization of each sensor surface was performed using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), X-ray photoelectron spectroscopy (XPS), quartz crystal microbalance (QCM), field-emission scanning electron microscopy (FE-SEM), and transmission electron microscopy (TEM). The experimental conditions affecting the analytical signal were optimized in terms of the amount of TBO, pH, temperature, binding time, applied potential, and the content ratio of monomer and MWCNT. The dynamic ranges of Hb and HbA1C were from 0.1 to 10µM and from 0.006 to 0.74µM, with detection limits of 82(±4.2)nM and 3.7(±0.8)nM, respectively. The reliability of the proposed microfluidic dual-sensor for a finger prick blood sample (1µL) was evaluated in parallel with a conventional method (HPLC) for point-of-care analysis.

Biosignal monitoring system for mobile telemedicine

This paper describes the design of a prototype integrated mobile telemedicine system that is compatible with existing public mobile telecommunication network, CDMA 1xEVDO. The mobile telemedicine system consists of two parts. One is a physiological signal measuring part, and the other is a PC system for the signal processing and telecommunication. The system uses NetMeeting to transmit video, audio and patient biosignals from a moving ambulance to a hospital and delivers to the personal computer of the doctor. The patient biosignals are noninvasive blood pressure (NIBP), arterial oxygen saturation (SpO/sub 2/), respiration pattern, electrocardiogram (ECG), heart sound, body core temperature and blood glucose concentration. For the emergency medicine, vital signs are focused and the remote medical monitoring, consulting, and health care are intended. The mobile telemedicine system was implemented, and tested for real time medical consultation during ambulance transport. This PC based mobile telemedicine system is flexible enough to accommodate newer components in wireless communication and portable sensing technologies. The present study suggests that the mobile telemedicine system using CDMA 1xEVDO is aids to patient monitoring and diagnosis as well as a convenient means of communications in the ambulance for the emergency medical care.

Vascular Variation of PTT and the Vascular Characteristic Index According to the Posture Change

The analysis of an arterial stiffness is essential for estimating the cardiovascular disease. Many indices suck as pulse transit time (PTT), reflection index (RI), stiffness index (ST) and characteristic impedance (Zc) are introduced to assess arterial stiffness. The purpose of this study is to analyze the variation aspect of PTT and the vascular characteristic index according to the posture change in the human body. The PTT is defined as the time interval between the peak of QRS complex in ECO and the characteristic point of the pulse wave. In this study, the characteristic point of the pulse wave is obtained using the maximum of the second derivative and peak point of PPQ signal, which is known to be noise resistant and to contribute a stable result. The vascular characteristic index was acquired through the analysis of waveform in peripheral pulse. The variation aspect of PTT and characteristic index according to the posture change were analyzed and the usefulness of those parameters was also evaluated. Experimental result indicated all parameters changed significantly according to the posture change. Therefore, proposed method can be an indispensable complement to existing methods for the non-invasive assessment of the vascular characteristics and body condition. It is possible to make ubiquitous healthcare monitoring because of simplicity, convenience and ease to access.

Emergency Detection System Using PDA Based on Self-Response Algorithm

The aged are faced with increasing risk for falls. The aged have the easily fragile bones than others. When falls have occurred, it is important to detect this emergency state because such events often lead to more serious illness or even death. A implementation of PDA system, for detection of emergency situation, was developed using 3-axis accelerometer in this paper as follows. The signals were acquired from the 3-axis accelerometer, and then transmitted to the PDA through Bluetooth module. This system can classify the human activity, and also detect the emergency state like falls. When the fall occurs, the system generates the alarm on the PDA. If a subject does not respond to the alarm, the system determines whether the current situation is an emergency state or not, and then sends some information to the emergency center in the case of urgent situation. Three different studies were conducted on 12 experimental subjects, with results indicating a good accuracy. The first study was performed to detect the posture change of human daily activity. The second study was performed to detect the correct direction of fall. The third study was conducted to check the classification of the daily physical activity. Each test was lasted at least I min. in third study. The output of acceleration signal was compared and evaluated by changing a various posture after attaching a 3-axis accelerometer module on the chest. The newly developed system has some important features such as portability, convenience and low cost. One of the main advantages of this system is that it is available at home healthcare environment. Another important feature lies in low cost to manufacture device. The implemented system can detect the fall well, so will be widely used in emergency situation.

Changes of Pulse Wave Velocity in Arm According to Characteristic Points of Pulse Wave

Pulse wave velocity has widely been used in the evaluation of atherosclerosis. In this study, we observed the change of pulse wave velocity according to characteristic points of pressure pulse waves which were recorded at brachial and radial artery. In order to evaluate the versatility of determination of the transit time between two points of measuring site, we measured PWV in seven methods : (1) the first derivative method, (2) the second derivative, (3) the minimum, (4) the intersecting a line tangent, (5) the maximum, (6) the middle point between minimum and maximum, (7) the intersecting two line tangents. Noninvasive brachial and radial pressure waveforms were recorded in 5 volunteers with external pressure transducers. The results showed that pulse wave velocity were dependent on the characteristic points.

Implementation and evaluation of the sensor assessing pressure and photoplethysmogram

Pulse sensors generally have characteristics that cause a analytical error by the interference of signals according to tiny motion of body and pressure applied to skin. To resolve this problem, we implemented the sensor that is capable of simultaneously measuring pressure and PPG(photoplethymogram) in a state attached to skin. Pressure and PPG was recorded at the finger and wrist respectively to evaluate the usefulness of the implemented sensor. Then, it was observed that the shape of PPG from sensor changed by pressure pushing down skin. Results of this study suggested that it is possible to monitor a degree of skin pressurization and to guarantee a reliable measurement by simultaneously measuring pressure and PPG using implemented integrated sensor when measuring PPG on the wrist or the finger.

Development of PC-based and portable high speed impedance analyzer for biosensor

For more convenient electrode-electrolyte interface impedance analysis in biosensor, a stand-alone impedance measurement system is required. In our study, we developed a PC-based portable system to analyze impedance of the electrochemical cell using microprocessor. The devised system consists of signal generator, programmable amplifiers, A/D converter, low pass filter, potentiostat, I/V converter, microprocessor, and PC interface. As a microprocessor, PIC16F877 which has the processing speed of 5 MIPS was used. For data acquisition, the sampling rate at 40 k samples/sec, resolution of 12 bit is used. RS-232 with 115.2 kbps speed is used for the PC communication. The square wave was used as stimuli signal for impedance analysis and voltage-controlled current measurement method of three-electrode-method were adopted. Acquired voltage and current data are calculated to multifrequency impedance signal after Fourier transform. To evaluate the implemented system, we set up the dummy cell as equivalent circuit of which was composed of resistor, parallel circuit of capacitor and resistor connected in parallel and measured the impedance of the dummy cell; the result showed that there exist accuracy within 5 % errors and reproduction within 1 % errors compared to output of Hioki LCR tester and HP impedance analyzer as a standard product. These results imply that it is possible to analyze electrode-electrolyte interface impedance quantitatively in biosensor and to implement the more portable high speed impedance analysis system compared to existing systems.

Measurement of Cardiac Pulse Transit Time using Photoplethysmography Sensor

In this study, we implemented the pulse transit time (PTT) system to examine usefulness of the monitoring method of distensibility and elasticity using photoplethysmography sensor in vivo. PTT is defined as the time interval between the peak of QRS complex in ECG signal and the maximum slope point of photoplethysmography. these two signals were converted to digital data by means of AID converter, then PTT was evaluated by heartbeat using PC. Results of analysis were displayed as a graph using spline interpolation method. The variance of PTT was measured repetitiously to verify efficiency of PTT system in resting state and hyperemic state. Repeated measurement of PTT was not same value but showed that coefficients of correlation were related with each other as 0.8302 (P

Performance comparison between multienzymes loaded single and dual electrodes for the simultaneous electrochemical detection of adenosine and metabolites in cancerous cells

The analytical performance of the multi enzymes loaded single electrode sensor (SES) and dual electrode sensor (DES) was compared for the detection of adenosine and metabolites. The SES was fabricated by covalent binding of tri-enzymes, adenosine deaminase (ADA), purine nucleoside phosphorylase (PNP), and xanthine oxidase (XO) along with hydrazine (Hyd) onto a functionalized conducting polymer [2,2:5,2-terthiophene-3-(p-benzoic acid)] (pTTBA). The enzyme reaction electrode in DES was fabricated by covalent binding of ADA and PNP onto pTTBA coated on Au nanoparticles. The detection electrode in DES was constructed by covalent binding of XO and Hyd onto pTTBA coated on porous Au. Due to the higher amount (3.5 folds) of the immobilized enzymes and Hyd onto the DES than SES, and the lower Michaelis constant (Km) value for DES (28.7 µM) compared to SES (36.1 µM), the sensitivity was significantly enhanced for the DES (8.2 folds). The dynamic range obtained using DES was from 0.5 nM to 120.0 µM with a detection limit of 1.43 nM ± 0.02, 0.76 nM ± 0.02, and 0.48 nM ± 0.01, for adenosine (AD), inosine (IN), and hypoxanthine (Hypo) respectively. Further, the DES was coupled with an electrochemical potential modulated microchannel for the separation and simultaneous detection of AD, IN, and Hypo in an extracellular matrix of cancerous (A549) and non-cancerous (Vero) cells. The sensor probe confirms a higher basal level of extracellular AD and its metabolites in cancer cells compared to normal cells. In addition, the effect of dipyridamole on released adenosine in A549 cells was investigated.