• Applied Chemistry for Engineering
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• v.33 no.2
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• pp.188-194
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• 2022

This work presents a non-destructive and straightforward approach to assemble a large-scale conductive electronic film made of a pre-treated single-walled carbon nanotube (SWCNT) solution. For effective electron transfer between the immobilized enzyme and SWCNT electronic film, we optimized the pre-treatment step of SWCNT with p-terphenyl-4,4"-dithiol and dithiothreitol. Glucose oxidase (GOx, a model enzyme in this study) was immobilized on the SWCNT electronic film following the positively charged polyelectrolyte layer deposition. The glucose detection was realized through effective electron transfer between the immobilized GOx and SWCNT electronic film at the negative potential value (-0.45 V vs. Ag/AgCl). The SWCNT electronic film-based glucose biosensor exhibited a sensitivity of 98 ㎂/mM·cm². In addition, the SWCNT electronic film biosensor showed the excellent selectivity (less than 4 % change) against a variety of redox-active interfering substances, such as ascorbic acid, uric acid, dopamine, and acetaminophen, by avoiding co-oxidation of the interfering substances at the negative potential value.

• Transactions of the Korean hydrogen and new energy society
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• v.27 no.4
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• pp.378-385
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• 2016

In this study, we synthesized a biocatalyst consisting of glucose oxidase (GOx), polyethyleneimine (PEI) and carbon nanotube (CNT) with addition of glutaraldehyde (GA)(GA/[GOx/PEI/CNT])for fabrication of glucose sensor. Main bonding of the GA/[GOx/PEI/CNT] catalyst was formed by crosslinking of functional end groups between GOx/PEI and GA. Catalytic activity of GA/[GOx/PEI/CNT] was quantified by UV-Vis and electrochemical measurements. As a result of that, high immobilization ratio of 199% than other catalyst (with only physical adsorption) and large sensitivity value of $13.4{\mu}A/cm^2/mM$ was gained. With estimation of the biosensor stability, it was found that the GA/[GOx/PEI/CNT] kept about 88% of its initial activity even after three weeks. It shows GA minimized the loss of GOx and improved sensing ability and stability compared with that using other biocatalysts.

• Korean Journal of Chemical Engineering
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• v.35 no.12
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• pp.2421-2429
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• 2018

Thiol-based self-assembled anchor linked to glucose oxidase (GOx) and gold nanoparticle (GNP) cluster is suggested to enhance the performance of glucose biosensor. By the adoption of thiol-based anchors, the activity of biocatalyst consisting of GOx, GNP, polyethyleneimine (PEI) and carbon nanotube (CNT) is improved because they play a crucial role in preventing the leaching out of GOx. They also promote electron collection and transfer, and this is due to a strong hydrophobic interaction between the active site of GOx and the aromatic ring of anchor, while the effect is optimized with the use of thiophenol anchor due to its simple configuration. Based on that, it is quantified that by the adoption of thiophenol as anchor, the current density of flavin adenine dinucleotide (FAD) redox reaction increases about 42%, electron transfer rate constant ($k_s$) is $9.1{\pm}0.1s^{-1}$ and the value is 26% higher than that of catalyst that does not use the anchor structure.

• 한국생물공학회:학술대회논문집
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• 2001.11a
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• pp.819-822
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• 2001

In this study a fiber optic biosensor has been developed to on-line monitor the concentrations of oxygen and glucose. The oxygen concentrations in solution and gas phase monitored by the fiber optic sensor has been compared with those by a dissolved oxygen electrode and an IR-type $O_2$ analyzer. The fiber optic glucose sensor has been made by immobilizing glucose oxidase on the tip of the optic fiber and used to on-line monitor the concentration of glucose in a fermentation process.

• Journal of the Korean Electrochemical Society
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• v.11 no.3
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• pp.170-175
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• 2008

Screen printed carbon electrodes (SPEs) modified with co-immobilized osmium-based redox polymers can be used to apply multi-detecting biosensors. In this study, we report our initial studies of multi-detecting biosensor concepts using two osmium-based redox polymers for horseradish peroxidase-mediated reduction of ${H_2}{O_2}$ coupled to glucose oxidase-mediated oxidation of glucose. We target to synthesize two osmium redox polymers of potentials use, a chloride-containing redox polymer ($E^{O'}$ + 0.520 vs. Ag/AgCl) and a methoxy-containing redox polymer $E^{O'}$ + 0.150 vs. Ag/AgCl). The former show good catalytic electrical signals with horseradish peroxidase and the latter's redox polymer is to be an effective redox mediator of glucose oxidation by glucose oxidase.

• Journal of Sensor Science and Technology
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• v.8 no.3
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• pp.247-252
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• 1999

The oxygen electrode of a biosensor needs enzyme immobilized membrane and a dialysis membrane to measure the oxygen concentration that remains after an enzyme reacts with its substrate. Accodingly, a single-layer PVA laminated CTA/PCL membrane was developed as an oxygen biosensor electrode. The enzymes were immobilized on a cellulose triacetate/polycarprolactone membrane using the 1,1'-carbonyl diimidazole(CDI) method, and then laminated with polyvinyl alcohol, aldehyde and acid. The alcohol oxidase and PVA laminated CTA/PCL membrane was tested with various concentration of enzyme substrates using a Yellow Springs Instrument(YSI) oxygen sensor. Under 5-10mmol substrates produced $0.37{\sim}0.83{\mu}A$(r=0.995) currents, and ater 8 weeks the glucose oxidase activity remained at about 56%, while the other activities remained very low. A SEM indicated a smooth surface and tightly attached PVA on the enzyme-immobilized CTA/PCL membranes.

• Food Science and Biotechnology
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• v.14 no.6
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• pp.743-746
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• 2005

A dipstick-type immunochemical biosensor for the detection of the organophosphorus insecticide fenthion was developed using a screen-printed electrode system as an amperometric transducer with polyclonal antibodies against fenthion as a bioreceptor. The assay of the biosensor involved competition between the pesticide in the sample and pesticide-glucose oxidase conjugate for binding to the antibody immobilized on the membrane. This was followed by measurement of the activity of the bound enzyme by the supply of the enzyme substrate (glucose) and amperometric determination of the enzyme reaction product ($H_2O_2$). The activity of the bound enzyme was inversely proportional to the concentration of pesticide. The optimized sensor system showed a linear response against the logarithm of the pesticide concentration ranging from $10^{-2}$ to $10^3\;{\mu}g/L$.

• 한국생물공학회:학술대회논문집
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• 2003.04a
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• pp.627-629
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• 2003

In this work fiber-optic biosensor that has been used in medical applications was developed. And we can monitored the concentration of glucose and lactate in blood sample by using developed fiber-optic glucose and lactate sensor. Glucose oxidase(GOD) and Lactate oxidase(LOD) were immobilized by using acrylamide adhesive and zeolite on the tip of the optic fiber.

• Journal of the Korean Electrochemical Society
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• v.11 no.3
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• pp.176-183
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• 2008

Redox complexes to transport electrodes from bioreactors to electrodes are very important part in electrochemical biosensor industry. A novel osmium redox complexes were synthesized by the coordinating pyridine group having different functional group at 4-position with osmium metal. Newly synthesized osmium complexes are described as ${[Os(dme-bpy)}_2{(ap-im)Cl]}^{+/2+}$, ${[Os(dme-bpy)}_2{(ap-im)Cl]}^{+/2+}$, ${[Os(dmo-bpy)}_2{(ap-im)Cl]}^{+/2+}$, ${[Os(dcl-bpy)}_2{(ap-im)Cl]}^{+/2+}$. We have been studied the electrochemical characteristics of these osmium complex with electrochemical techniques such as cyclic voltammetry and chronoamperommetry. Osmium redox complexes were immobilized on the screen printed carbon electrode(SPE) with deposited gold nanoparticles. The electrical signal converts the osmium redox films into an electrocatalyst for glucose oxidation. Each catalytic currents were related with the potentials of osmium complexes.

• Proceedings of the IEEK Conference
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• 2005.11a
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• pp.755-758
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• 2005

This paper describes the novel immunoassay sensing system for a portable clinical diagnosis system. It consists of a bead cage reactor and a CMOS integrated biosensor. It showed the simple and easy antibody coating method on beads by flow-through avidin biotin complex technology in a microfluidic device. It showed just 90 nL sample consumption and good result for the application of alpha feto protein. The bead cage reactor has the role of the antibody coating, antigen binding and enzyme linking for the electrochemical sensing method. The CMOS biosensor consists of ISFET (ion selective field effect transistor) biosensor and temperature sensor for detecting pH that is the byproduct of enzyme reaction. The sensitivity is 8 $kHz/^{\circ}C$ in a temperature sensor and 33 mV/pH in a pH sensor. After filling the 15 um polystyrene beads in bead cage, antibody flowed and reacted to beads. Subsequently, the biotinylated antigen flowed and bound to the antibody and GOD (glucose oxidase)-avidin conjugate flowed and reacted to the biotin of the biotinylated antigen. After this reaction process, glucose solution flowed and reacted to the GOD on beads. The hydrogen was generated by glucose-GOD reaction. And it was detected by the pH sensor.