Disposable Strip-Type Biosensors for Amperometric Determination of Galactose

Gwon, Kihak,Lee, Seonhwa,Nam, Hakhyun,Shin, Jae Ho The Korean Electrochemical Society 2020 Journal of electrochemical science and technology Vol.11 No.3

A development of disposable strip-type galactose sensor for point-of-care testing (POCT) was studied, which was constructed using screen-printed carbon electrodes. Galactose levels were determined by the redox reaction of galactose oxidase in the presence of potassium ferricyanide as an electron transfer mediator in a small sample volume (i.e., less than 1 µL). The optimal performance of biosensor was systematically designated by varying applied potential, operating pH, mediator concentration, and amount of enzyme on the electrode. The sensor system was identified as a highly active for the galactose measurement in terms of the sensitivity (slope = 4.76 ± 0.05 nA/µM) with high sensor-to-sensor reproducibility, the linearity (R² = 0.9915 in galactose concentration range from 0 to 400 µM), and response time (t_95% = <17 s). A lower applied potential (i.e., 0.25 V vs. Ag/AgCl) allowed to minimize interference from readily oxidizable metabolites such as ascorbic acid, acetaminophen, uric acid, and acetoacetic acid. The proposed galactose sensor represents a promising system with advantage for use in POCT.

Pro-apoptotic Effect of Pifthrin-α on Preimplantation Porcine In Vitro Fertilized Embryo Development

Brendan Mulligan,Jong-Nam Oh,Jae-Yeon Hwang,Hyung-Min Kim,Kwang-Hwan Choi,Chang-Kyu Lee,Hakhyun Ka 한국동물생명공학회(구 한국동물번식학회) 2012 발생공학 국제심포지엄 및 학술대회 Vol.2012 No.1

전기화학적 효소면역센서

김민선,장봉화,허성민,신혜라,남학현,차근식 경북대학교 센서기술연구소 2002 센서技術學術大會論文集 Vol.13 No.1

흐름계를 이용한 크롬도금 용액의 Cr(Ⅲ)와 Cr(Ⅵ)의 분광학적 동시 분석 방법

김선관,남학현,소재춘,이원,차근식,한상현,Kim, Sun Kwan,Nam, Hakhyun,So, Jae Chun,Lee, Won,Cha, Geun Sig,Han, Sang Hyun 대한화학회 1995 대한화학회지 Vol.39 No.2

크롬도금 용액에 공존하고 있는 Cr(III)와 Cr(VI)의 양을 자외선/가시광선 분광기에 장착한 흐름계 장치를 이용하여 시료당 5분 이내에 두 가지 물질의 양을 동시에 분석하는 방법을 개발하였다. Cr(III)와 Cr(VI)는 각각 580 nm와 440 nm에서 0.05 g/L와 0.005 g/L 이상의 범위에서 Beer-Lambert 법칙에 따르는 특성 ${\lambda}_{max}$를 나타내며, 이 파장들에서의 흡광도는 pH<4의 조건에서는 pH변화에 거의 영향을 받지 않았다. 따라서 일반적으로 크롬의 농도가 수 g/L인 후처리 크롬 도금조의 용액을 흐름계의 장치에서 pH=1의 황산 용액으로 묽힌 후, 자외선/가시광선 분광기로 측정하면 Cr(III)와 Cr(VI)의 양 및 총 크롬의 양을 기존의 산화-환원 적정 방법(최소 40분/sample)보다 간편하고 신속정확하게 동시 정량할 수 있었다. 이 장치는 설치 및 사용이 간단하고, 설치 비용이 저렴하므로 많은 도금 산업 현장에서 용이하게 응용할 수 있다. The amount of Cr(Ⅲ) and Cr(Ⅵ) in a chromium plating solution could be determined simultaneously within five minutes using UV/VIS spectrophotometer coupled with a flow-through analysis(FTA) setup. The λmax's at 580 nm and 440 nm which correspond to Cr(Ⅲ) and Cr(Ⅵ), respectively, well obey the Beer-Lambert law in the range over 0.05 g/L for Cr(Ⅲ) and 0.005 g/L for Cr(Ⅵ). when the pH of the sample is less than 4.0, the absorption extinction coefficients of those peaks are not much dependent on the proton concentration. The amount of Cr(Ⅲ) and Cr(Ⅵ), and the total chromium in post treatment chromium plating solution, which normally has few g/L of Cr concentration, could be easily measured using UV/VIS spectrophotometry after the sample had been diluted with sulfuric acid of pH=1.0 in the flow-through analysis setup; this method is far more convenient and faster than the common redox titration (which requires at least 40 min/sample) method, while the accuracy of the method is highly comparable to conventional titrimetric method. Since the implementation of an PTA-UV/VIS setup in any plating industry is cost effective and easy to operate, the analytic method described in this paper may be applied directly for in situ analysis of plating solutions.

Electroanalytical Applications Based on Carbon Nanotube/Prussian Blue Screen-printable Composite

Jun Ho Shim,Jae Seon Lee,Geun Sig Cha,Hakhyun Nam 대한화학회 2010 Bulletin of the Korean Chemical Society Vol.31 No.6

A single step fabrication process of carbon nanotube/Prussian Blue (CNT/PB) paste electrodes based on screen printing technology has been studied as an amperometric sensor for the determination of hydrogen peroxide and free chlorine. Compared to the classical carbon paste (CP) electrode, the CNT paste electrode greatly enhanced the response in the presence of hydrogen peroxide due to the electrocatalytic activity of the CNT. Based on the CNT/binder paste,PB was also incorporated into a network of CNT paste and characterized. The best electroanalytical properties of PB-mixed sensors to hydrogen peroxide were obtained with PB ratio of 10 wt % composition, which showed fast response time (t90 ≤ 5 s; 0.2 - 0.3 mM), low detection limit of 1.0 μM, good linear response in the range from 5.0 ×10‒5 - 1.0 × 10‒3 mol L‒1 (r2 = 0.9998), and high sensitivity of ‒8.21 μA mM‒1. In order to confirm the enhanced electrochemical properties of CNT/PB electrode, the sensor was further applied for the determination of chlorine in water, which exhibited a linear response behavior in the range of 50 - 2000 ppb for chlorine with a slope of 1.10 μA ppm‒1 (r2 = 9971).

A Self-Sampling-and-Flow Biosensor for Continuous Monitoring

Zhang, Fenghua,Kim, Jong ,Sik,Cui, Gang,Cha, Geun ,Sig,Nam, Hakhyun WILEY-VCH Verlag 2005 Electroanalysis Vol.17 No.8

<P>A self-sampling-and-flow biosensor was fabricated by sandwiching a nitrocellulose strip on the working electrode side of the double-sided microporous gold electrodes and a wicking pad on the counter electrode side. The double-sided microporous electrodes were formed by plasma sputtering of gold on a porous nylon substrate. Sample was taken up to the enzyme-immobilized working electrode by the capillary action of the front nitrocellulose strip dipped into the sample solution, analyzed electrochemically at the enzyme-immobilized electrode, and diffuses out to the backside wicking pad through the micropores of the electrodes, constituting a complete flow cell device with no mechanical liquid-transporting device. Biosensor was formed by co-immobilizing the glucose oxidase and electron transfer mediator (ferrocene acetic acid) on the thioctic acid self-assembled monolayer-modified working electrode. A typical response time of the biosensor was about 5 min with the sensitivity of 2.98 nA/mM glucose, providing linear response up to 22.5 mM. To demonstrate the use of self-sampling-and-flow biosensor, the consumption rate of glucose in the presence of yeast was monitored for five days. </P>

Silicone Rubber Blended with Polyurethane as the Matrix for Ion-Selective Membrane Electrodes

Lee, Hyun Jung,Rho, Kyung Lae,Kim, Chang Yong,Oh, Bong Kyun,Cha, Geun Sig,Nam, Hakhyun 한국분석과학회 1995 분석과학 Vol.8 No.4

Silicone rubber-based sodium-selective membranes are developed for solid-state ion sensors. It was shown that the potetiometric performance of SR-based membranes are greatly dependent on the type of neutral carriers employed; among the three ionophores, N,N,N',N'-tetracyclohexyl-1,2-phenylenedioxydiacetamide (ETH 2120), bis[(12-crown-4)methyl]dodecylmethylmalonate (D12C4DMM) and monensin methyl ester (MME), examined, only ETH 2120 was compatible with the SR-based matrix. Addition of about 20 wt% plasticizer to the SR-based matrix provided the resulting membranes with potentiometric properties essentially equivalent to those of the corresponding PVC-based membranes. Owing to the strong adhesive strength of SR-based membranes, the CWEs coated \vith those membranes exhibited long lifetime with conventional electrode-like performance. Blending of PU into the SR matrix increased the lifetime of CWEs from two weeks to one month.

Gold Nanoparticle-Based Mediatorless Biosensor Prepared on Microporous Electrode

Zhang, Fenghua,Cho, Soon ,Sam,Yang, Soon ,Hye,Seo, Seong ,Suk,Cha, Geun ,Sig,Nam, Hakhyun WILEY-VCH Verlag 2006 Electroanalysis Vol.18 No.3

<P>A mediatorless biosensor was fabricated with a double-sided microporous gold electrode by successively immobilizing a mixed self-assembled monolayer (SAM) comprising carboxylic-acid- and thiol-terminated thiolate (dl-thiorphan and 1,8-octanedithiol), glucose oxidase (GOx) and finally gold nanoparticle (Au NP) on one working side. The double-sided microporous gold electrodes were formed by plasma sputtering of gold on a porous nylon substrate, yielding a face-to-face type two-electrode electrochemical cell. While the straight chain molecule 1,8-octanedithiol forms a dense insulating monolayer, the side armed dl-thiorphan forms a low density layer for the diffusion of redox couples to the electrode surface. The mixed SAM not only provided the linking functional groups for both enzyme and Au NP but also resulted in the appropriately spaced monolayer for direct electron tansfer (ET) process from the center of the redox enzyme to the electrode surface. After covalently immobilizing GOx onto the carboxylic-acid-terminated monolayer, Au NP was easily immobilized to both enzyme and nearby thiols by simple dispensing of the colloidal gold solution. It was observed that the resulting amperometric biosensor exhibited quantitatively the same response to glucose in the presence and in the absence of dissolved oxygen, which evidence that the Au NPs immobilized on and around the GOx promote direct ET from the enzymes to the electrode, assuming the role of a common redox mediator.</P>

유리염소 측정을 위한 일회용 스트립 센서

김승기,강태영,차근식,남학현,신재호,Kim, Seung Ki,Kang, Tae Young,Cha, Geun Sig,Nam, Hakhyun,Shin, Jae Ho 한국전기화학회 2012 한국전기화학회지 Vol.15 No.4

수질 분석에서 염소 소독제 잔류량 측정은 세균학적 안전성 확보와 염소의 과다 주입을 억제하기 위한 수단으로 매우 중요한 의미를 갖는다. 이러한 휴대용 잔류염소 측정기 개발을 위한 일회용 유리염소 스트립 센서를 스크린 프린팅 기술을 이용한 탄소 전극으로 제작하였다. 탄소 전극은 금과 백금 전극에 비해 결합염소(특히 $NH_2Cl$) 방해종에 대한 영향이 적었으며, -0.3 V(vs. Ag/AgCl) 인가전위에서 유리염소에 대해 안정한 감응성을 나타냈다. 이렇게 제작된 탄소 전극에 모세관현상으로 일정량의 시료를 재현성 있게 도입할 수 있는 유로구조를 갖는 일회용 스트립센서로 제작하였고, 잔류 유리염소의 분석에 적용하였다. The measurement of residual chlorine as a disinfectant is very important to ensure the safety against the pathogenic microbes and to suppress injection. The portable free chlorine sensor was fabricated with a disposable strip format by a screen printing method. The strip sensors prepared with a carbon-Ag/AgCl(cathode-anode) combination exhibited less interfering responses towards combined chlorine species(especially $NHCl_2$) and oxygen than the sensors prepared with other metals(i.e., gold and platinum). Free chlorine was determined chronoamperometrically with carbon-based electrodes at an applied potential of -0.3 V(vs. Ag/AgCl). A channel was built on the strip-type electrode for easy sampling, and the resulting strip sensors were employed to determine the concentrations of residual free chlorine.

N-히드록시숙신이미드로 수식한 탄소반죽전극을 이용한 도파민의 전기화학적 측정

유재현,우병욱,김순신,엄정희,남학현,차근식,Yoo Jae Hyun,Yoo Byung Wook,Kim Soon Shin,Uhm Jung Hee,Nam Hakhyun,Cha Geun Sig 한국전기화학회 2001 한국전기화학회지 Vol.4 No.3

활성화된 탄소반죽전극 표면을 N피드록시숙신이미드(NHS)층으로 수식한 후, 이 전극을 이용하여 square-wave voltammetry방법으로 과량의 아스코빅산 존재 하에서 도파민을 측정하였다. 수식된 전극의 특성은 도파민과 아스코빅산 혼합용액에서 순한전압전류법을 이용하여 조사하였다. 도파민과 아스코빅산의 산화 피크의 분리는 시료용액의 pH에 큰 영향을 받았으며, pH 4.0에서 최대의 피크분리(172mv)를 보였다. 따라서 도파민을 정량하기 위한 square-wave voltammeoy는 140 mM NaCl을 포함하는 100 mM phosphate buffered saline (PBS)의 pH 4.0 조건에서 수행하였다. NHS로 수식된 전극은 0.2mM 아스코빅 산의 존재 하에서 도파민의 농도 $5.0\times10^{-2}$까지 검출한계와 감응기울기 $6.1{\mu}A/{\mu}M$의 감도를 나타내었다. 반면 수식되지 않은 전극은 $1.0{\mu}M$의 검출한계와 $0.93{\mu}A/{\mu}M$ 기울기를 나타내어 표면에 수식된 N-히드록시숙신이미드가 도파민의 감응을 촉진함을 보여주었다. An activated carbon paste electrode was modified with the N-Hydroxysuccinimide(NHS) layer and applied to determine the dopamine in the presence of an excess ascorbic acid using square-wave voltammetry. The electrochemical properties of the modified electrode were examined in the solution containing dopamine/ascorbic acid using cyclic voltammetry(CV): the separation between the oxidation peaks of dopamine and ascorbic acid was largely dependent on the pH of the sample solution and became maximum at pH 4.0. Hence, the square-wave voltammetric determination of dopamine was carried out in a pH 4.0, 100mM phosphate buffer saline(PBS) containing 140mM NaCl. The detection limit and response slop were improved from $1.0{\mu}M\;to\;5.0\times10^{-2}{\mu}M\;and\;from\;0.93{\mu}A/{\mu}M\;to\;6.1{\mu}A/{\mu}M$, respectively, upon modification of the electrode surface by NHS.