Publications by authors named "Dong-Hyung Kim"

32 Publications

Histomorphometric Evaluation of Socket Preservation Using Autogenous Tooth Biomaterial and BM-MSC in Dogs.

Scanning 2021 12;2021:6676149. Epub 2021 May 12.

Department of Oral and Maxillofacial Surgery, Graduate School of Clinical Dentistry, Korea University, Seoul 08308, Republic of Korea.

This study is aimed at assessing the dimensional alterations occurring in the alveolar bone after premolar extraction in dogs with histomorphometric and histological analysis. After atraumatic premolar extraction, tooth-derived bone graft material was grafted in the extraction socket of the premolar region in the lower jaws of six dogs in two experimental groups. In the second experimental group, BM-MSCs were added together with the graft. The control was left untreated on the opposite side. After twelve weeks, all six animals were sacrificed. Differences in alveolar bone height crests lingually and buccally, and alveolar bone width at 1, 3, and 5 mm infracrestally, were examined. Histologic study revealed osteoconductive properties of tooth biomaterial. A statistically significant difference was detected between the test and control groups. In the test groups, a reduced loss of vertical and horizontal alveolar bone dimensions compared with the control group was observed. Tooth bone graft material may be considered useful for alveolar ridge preservation after tooth extraction, as it could limit the natural bone resorption process.
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http://dx.doi.org/10.1155/2021/6676149DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8137288PMC
May 2021

A Membrane Filter-Assisted Mammalian Cell-Based Biosensor Enabling 3D Culture and Pathogen Detection.

Sensors (Basel) 2021 Apr 26;21(9). Epub 2021 Apr 26.

Division of Interdisciplinary Materials Measurement Institute, Korea Research Institute of Standards and Science, Daejeon 34113, Korea.

We have developed a membrane filter-assisted cell-based biosensing platform by using a polyester membrane as a three-dimensional (3D) cell culture scaffold in which cells can be grown by physical attachment. The membrane was simply treated with ethanol to increase surficial hydrophobicity, inducing the stable settlement of cells via gravity. The 3D membrane scaffold was able to provide a relatively longer cell incubation time (up to 16 days) as compared to a common two-dimensional (2D) cell culture environment. For a practical application, we fabricated a cylindrical cartridge to support the scaffold membranes stacked inside the cartridge, enabling not only the maintenance of a certain volume of culture media but also the simple exchange of media in a flow-through manner. The cartridge-type cell-based analytical system was exemplified for pathogen detection by measuring the quantities of toll-like receptor 1 (TLR1) induced by applying a lysate of and live , respectively, providing a fast, convenient colorimetric TLR1 immunoassay. The color images of membranes were digitized to obtain the response signals. We expect the method to further be applied as an alternative tool to animal testing in various research areas such as cosmetic toxicity and drug efficiency.
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http://dx.doi.org/10.3390/s21093042DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8123675PMC
April 2021

Normal-incidence type solution immersed silicon (SIS) biosensor for ultra-sensitive, label-free detection of cardiac troponin I.

Biosens Bioelectron 2020 Nov 21;168:112525. Epub 2020 Aug 21.

Division of Interdisciplinary Materials Measurement Institute, Korea Research Institute of Standards and Science, 267 Gajeongno, Yuseong-Gu, Daejeon, 34113, South Korea. Electronic address:

Early diagnosis of acute myocardial infarction (AMI) significantly reduce the mortality rate and can be achieved via high-sensitive detection of AMI specific cardiac troponin I (cTnI) biomarker. Here, we present normal-incident type solution-immersed silicon (NI-SIS) ellipsometric biosensor, designed for ultra-high sensitive, high-throughput, label-free detection of the target protein. The NI-SIS sensors are equipped with a specially designed prism that maintains the angle of incidence close to the Brewster angle during operation, which significantly reduces SIS noise signals induced by the refractive index fluctuations of the surrounding medium, improves the signal-to-noise ratio, in-results lowers the detection limit. We applied NI-SIS biosensor for ultra-sensitive detection of cTnI biomarkers in human serum. The optimized sensor chip fabrication and detection operation procedures are proposed. The wide linear concentration ranges of fg/mL to ng/mL is achieved with the detection limit of 22.0 fg/mL of cTnI. The analytical correlation was assessed by linear regression analysis with the results of the Pathfast reference system. These impressive biosensing capabilities of NI-SIS technology have huge potentials for accurate detection of target species in different application areas, such as diagnosis, drug discovery, and food contaminations.
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http://dx.doi.org/10.1016/j.bios.2020.112525DOI Listing
November 2020

Bipolar Energetics and Bifunctional Catalytic Activity of a Nanocrystalline Ru Thin-Film Enable High-Performance Photoelectrochemical Water Reduction and Oxidation.

ACS Appl Mater Interfaces 2020 Apr 30;12(14):16402-16410. Epub 2020 Mar 30.

Departments of Materials Science and Chemical Engineering, Hanyang University, 55 Hanyangdaehak-ro, Sangnok-gu, Ansan, Kyeonggi-do 15588, Republic of Korea.

Photoelectrochemical (PEC) cells, which represent a promising technology for the production of hydrogen fuel through water splitting reactions, must meet two criteria to achieve high-performance operation: (i) a high thermodynamic open-circuit potential and (ii) a low kinetic overpotential. Herein, we achieved these criteria in both an oxygen-evolving n-Si photoanode and hydrogen-evolving p-Si photocathode by simple electrodeposition of a nanocrystalline thin film of Ru. The bifunctional electrocatalytic activity of the nanocrystalline Ru led to low overpotentials in both the acidic oxygen evolution reaction (0.27 V) and alkaline hydrogen evolution reaction (0.04 V). In addition, the nanocrystalline Ru/Si junctions influenced the interface energetics via the induction of an extrinsic electrochemical potential on the surface of the Ru nanocrystals through a redox reaction rather than the chemical potential of the electrons (work function) of bulk Ru. The nanocrystalline Ru film exhibited bipolar applicability, enabling both Ru/n-Si and Ru/p-Si junctions with high values of 0.63 and 0.5 V, respectively. As a result, the n-Si photoanode in the acidic electrolyte and the p-Si photocathode in the alkaline electrolyte generated a photocurrent of 10 mA/cm at record values of 0.87 and 0.42 V versus the reversible hydrogen electrode, respectively. These results provide insight into the development of high-performance PEC cells based on a nanocrystalline electrocatalyst.
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http://dx.doi.org/10.1021/acsami.0c00367DOI Listing
April 2020

Electrochemical biosensors: perspective on functional nanomaterials for on-site analysis.

Biomater Res 2020 4;24. Epub 2020 Feb 4.

3Department of Biomedical Engineering, College of Health Science, Eulji University, Seongnam, 13135 Republic of Korea.

Background: The electrochemical biosensor is one of the typical sensing devices based on transducing the biochemical events to electrical signals. In this type of sensor, an electrode is a key component that is employed as a solid support for immobilization of biomolecules and electron movement. Thanks to numerous nanomaterials that possess the large surface area, synergic effects are enabled by improving loading capacity and the mass transport of reactants for achieving high performance in terms of analytical sensitivity.

Main Body: We categorized the current electrochemical biosensors into two groups, carbon-based (carbon nanotubes and graphene) and non-carbon-based nanomaterials (metallic and silica nanoparticles, nanowire, and indium tin oxide, organic materials). The carbon allotropes can be employed as an electrode and supporting scaffolds due to their large active surface area as well as an effective electron transfer rate. We also discussed the non-carbon nanomaterials that are used as alternative supporting components of the electrode for improving the electrochemical properties of biosensors.

Conclusion: Although several functional nanomaterials have provided the innovative solid substrate for high performances, developing on-site version of biosensor that meets enough sensitivity along with high reproducibility still remains a challenge. In particular, the matrix interference from real samples which seriously affects the biomolecular interaction still remains the most critical issues that need to be solved for practical aspect in the electrochemical biosensor.
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http://dx.doi.org/10.1186/s40824-019-0181-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7001310PMC
February 2020

A semiconductor junction photoelectrochemical device without a depletion region.

Nanoscale 2019 Dec 26;11(47):23013-23020. Epub 2019 Nov 26.

Department of Materials Science and Chemical Engineering, Hanyang University, 55 Hanyangdaehak-ro, Sangnok-gu, Ansan, Kyeonggi-do 15588, Republic of Korea.

Semiconductor junctions are believed to form a depletion region at the band edge of the semiconductor as the chemical potentials for electrons (work functions) are aligned to the same level. Here, we demonstrated that ultrathin Ni film (less than 4 nm thick)/Si junction-based photoelectrochemical (PEC) devices have no depletion region due to three distinct phenomena: (i) the electrostatic or electrochemical potential extrinsically charged to the electrolytic-capacitive Ni surface dominates rather than the chemical potential of electrons (work function) of the bulk Ni, (ii) the charged potential is dynamically variable depending on the reaction and is rapidly volatile so as not to be constant; therefore, (iii) the charged potential is misaligned with the chemical potential of Si under equivalent circuit conditions. Such junction PEC devices were shown to follow a novel operating principle in which the output voltage (open circuit potential) is generated by the electrochemical potential charged at the Ni surface, and not by the light-induced potential (photovoltage) in Si. In addition, due to the bipolar charging nature, the ultrathin Ni film was effective in achieving a high open circuit potential in both p-Si photocathodes (0.57 V) and n-Si photoanodes (0.45 V). These anomalous results were not explained by the classical Schottky diode model based on the equilibrium of diffusion-drift current but by establishing a new model based on the equilibrium of the diffusion-charging current without accounting for the depletion region. Our findings provide an explanation for the unexpected results of the nanostructured PEC devices and insight into a new design that can overcome conventional limitations.
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http://dx.doi.org/10.1039/c9nr08172kDOI Listing
December 2019

Effect of autoclave sterilization on cyclic fatigue and torsional fracture resistance of NiTi rotary instruments.

Odontology 2020 Apr 11;108(2):194-201. Epub 2019 Sep 11.

Department of Conservative Dentistry, School of Dentistry, Kyung Hee University, Seoul, Republic of Korea.

The purpose of this study is to assess the effect of autoclave sterilization on the cyclic fatigue and torsional fracture resistance of ProTaper Universal (PTU), K3XF, HyFlex EDM (EDM), and TF adaptive (TFA). Sixty instruments from each file type were divided into two categories for cyclic fatigue group (CGr) and torsional fracture group (TGr). CGr and TGr were divided into three subgroups, respectively, consisting of ten instruments from each file type. Cyclic fatigue fracture test was performed using artificial canal made of stainless steel, and the mean number of cycles to failure (NCF) were determined. CGr1, the files were tested to establish baseline for NCF; CGr2, the files were tested cyclic fatigue after 10 cycles of autoclave; CGr3, instruments were autoclaved after being cycled to 25, 50, and 75% of corresponding NCF determined in CGr1, followed by cyclic fatigue test. The torsional fracture test was performed without autoclave (TGr1), after 3-cycle autoclave (TGr2), and 7-cycle autoclave (TGr3), respectively, which evaluated maximum torque and angular deflection. NCF, maximum torque and angular deflection were compared using one-way ANOVA with Bonferroni test. Two-way ANOVA was performed to determine the interaction between 'autoclave treatment' and 'type of NiTi file'. EDM showed highest NCF within the same autoclave treatment. TFA presented the lowest maximum torque and the highest angular deflection, and PTU presented the lowest angular deflection. Within the same NiTi file systems, most of NCF, maximum torque and angular deflection of tested files were not significantly influenced by autoclave condition.
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http://dx.doi.org/10.1007/s10266-019-00453-3DOI Listing
April 2020

PAS1-modified optical SIS sensor for highly sensitive and specific detection of toluene.

Biosens Bioelectron 2019 Sep 26;141:111469. Epub 2019 Jun 26.

Bionanotechnology Research Center, 125 Gwahangno, Yuseong-Gu, Daejeon, 34141, South Korea; KRIBB School, University of Science and Technology (UST), 217 Gajeongno, Yuseong-Gu, Daejeon, 34113, South Korea; Department of Biology, College of Arts & Sciences, Tuskegee University, 36088, USA. Electronic address:

We report on a novel solution immersed silicon (SIS) sensor modified with bio-receptor to detect toluene. To perform this approach, bio-receptor PAS1 which specifically interacts with toluene was chosen as a capture agent for SIS ellipsometric sensing. We constructed wild PAS1 and mutant PAS1 (F46A and F79Y) which are toluene binding-defective. Especially, we utilized an easily accessible capturing approach based on silica binding peptide (SBP) for direct immobilization of PAS1 on the SiO surfaces. After the immobilization of SBP-tagged PAS1 to the sensing layers, PAS1-based SIS sensor was evaluated for its ability to recognize toluene. As a result, a significant up-shift in Psi (Ψ) was clearly observed with a low limit of detection (LOD) of 0.1 μM, when treated with toluene on wild PAS1-surface, but not on mutant PAS1-sensing layers, indicating the selective interactions between PAS1 and toluene molecule. The PAS1-SIS sensor showed no changes in Psi (Ψ), if any, negligible, when exposed to benzene, phenol, xylene and 4-nitrophenol as negative controls, thereby demonstrating the specificity of interaction between PAS1 and toluene. Taken together, our results strongly indicate that PAS1-modified ellipsometry sensor can provide a high fidelity system for the accurate and selective detection of toluene.
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http://dx.doi.org/10.1016/j.bios.2019.111469DOI Listing
September 2019

Seebeck-voltage-triggered self-biased photoelectrochemical water splitting using HfO/SiO bi-layer protected Si photocathodes.

Sci Rep 2019 Jun 24;9(1):9132. Epub 2019 Jun 24.

Department of Materials and Chemical Engineering, Hanyang University, 55 Hanyangdaehak-ro, Sangnok-gu, Ansan, Kyeonggi-do, 15588, Republic of Korea.

The use of a photoelectrochemical device is an efficient method of converting solar energy into hydrogen fuel via water splitting reactions. One of the best photoelectrode materials is Si, which absorbs a broad wavelength range of incident light and produces a high photocurrent level (~44 mA·cm). However, the maximum photovoltage that can be generated in single-junction Si devices (~0.75 V) is much lower than the voltage required for a water splitting reaction (>1.6 V). In addition, the Si surface is electrochemically oxidized or reduced when it comes into direct contact with the aqueous electrolyte. Here, we propose the hybridization of the photoelectrochemical device with a thermoelectric device, where the Seebeck voltage generated by the thermal energy triggers the self-biased water splitting reaction without compromising the photocurrent level at 42 mA cm. In this hybrid device p-Si, where the surface is protected by HfO/SiO bilayers, is used as a photocathode. The HfO exhibits high corrosion resistance and protection ability, thereby ensuring stability. On applying the Seebeck voltage, the tunneling barrier of HfO is placed at a negligible energy level in the electron transfer from Si to the electrolyte, showing charge transfer kinetics independent of the HfO thickness. These findings serve as a proof-of-concept of the stable and high-efficiency production of hydrogen fuel by the photoelectrochemical-thermoelectric hybrid devices.
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http://dx.doi.org/10.1038/s41598-019-45672-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6591395PMC
June 2019

Solid-State Rechargeable Zinc-Air Battery with Long Shelf Life Based on Nanoengineered Polymer Electrolyte.

ChemSusChem 2018 Sep 10;11(18):3215-3224. Epub 2018 Aug 10.

Department of Materials Science and Chemical Engineering, Hanyang University, Ansan, Gyeonggi-do, 15588, South Korea.

Zinc-air batteries (ZABs) are vulnerable to the ambient environment (e.g., humidity and CO ), and have serious selfdischarge issues, resulting in a short shelf life. To overcome these challenges, a near-neutral quaternary ammonium (QA) functionalized polyvinyl alcohol electrolyte membrane (different from conventional alkali-type membranes) has been developed. QA functionalization leads to the formation of interconnected nanochannels by creating hydrophilic/-phobic separations at the nanoscale. These nanochannels selectively transport OH ions with a reduced migration barrier, while inhibiting [Zn(NH ) ] crossover. Owing to the superior water retention ability and enhanced chemical stability of the membrane, the solid-state zinc-air battery (SZAB) displays outstanding flexibility, a promising cycle lifetime, and a large volumetric energy density. More importantly, the self-discharge rate of SZAB is depressed to less than 7 % per month, and the fully dehydrated SZAB could recover its rechargeability upon replenishment of the solution of NH Cl.
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http://dx.doi.org/10.1002/cssc.201801274DOI Listing
September 2018

Current Technologies of Electrochemical Immunosensors: Perspective on Signal Amplification.

Sensors (Basel) 2018 Jan 12;18(1). Epub 2018 Jan 12.

Korea Research Institute of Standards and Science, P.O. Box 102, Yuseong, Daejon 34113, Korea.

An electrochemical immunosensor employs antibodies as capture and detection means to produce electrical charges for the quantitative analysis of target molecules. This sensor type can be utilized as a miniaturized device for the detection of point-of-care testing (POCT). Achieving high-performance analysis regarding sensitivity has been one of the key issues with developing this type of biosensor system. Many modern nanotechnology efforts allowed for the development of innovative electrochemical biosensors with high sensitivity by employing various nanomaterials that facilitate the electron transfer and carrying capacity of signal tracers in combination with surface modification and bioconjugation techniques. In this review, we introduce novel nanomaterials (e.g., carbon nanotube, graphene, indium tin oxide, nanowire and metallic nanoparticles) in order to construct a high-performance electrode. Also, we describe how to increase the number of signal tracers by employing nanomaterials as carriers and making the polymeric enzyme complex associated with redox cycling for signal amplification. The pros and cons of each method are considered throughout this review. We expect that these reviewed strategies for signal enhancement will be applied to the next versions of lateral-flow paper chromatography and microfluidic immunosensor, which are considered the most practical POCT biosensor platforms.
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http://dx.doi.org/10.3390/s18010207DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5796447PMC
January 2018

Hierarchically Designed 3D Holey CN Aerogels as Bifunctional Oxygen Electrodes for Flexible and Rechargeable Zn-Air Batteries.

ACS Nano 2018 01 26;12(1):596-608. Epub 2017 Dec 26.

Department of Materials and Chemical Engineering, ‡Department of Bionano Technology, and §Department of Applied Chemistry, Hanyang University , Ansan, Kyunggido 15588, Republic of Korea.

The future of electrochemical energy storage spotlights on the designed formation of highly efficient and robust bifunctional oxygen electrocatalysts that facilitate advanced rechargeable metal-air batteries. We introduce a scalable facile strategy for the construction of a hierarchical three-dimensional sulfur-modulated holey CN aerogels (S-CNA) as bifunctional catalysts for Zn-air and Li-O batteries. The S-CNA exhibited ultrahigh surface area (∼1943 m g) and superb electrocatalytic activities with lowest reversible oxygen electrode index ∼0.65 V, outperforms the highly active bifunctional and commercial (Pt/C and RuO) catalysts. Density functional theory and experimental results reveal that the favorable electronic structure and atomic coordination of holey C-N skeleton enable the reversible oxygen reactions. The resulting Zn-air batteries with liquid electrolytes and the solid-state batteries with S-CNA air cathodes exhibit superb energy densities (958 and 862 Wh kg), low charge-discharge polarizations, excellent reversibility, and ultralong cycling lives (750 and 460 h) than the commercial Pt/C+RuO catalysts, respectively. Notably, Li-O batteries with S-CNA demonstrated an outstanding specific capacity of ∼648.7 mA h g and reversible charge-discharge potentials over 200 cycles, illustrating great potential for commercial next-generation rechargeable power sources of flexible electronics.
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http://dx.doi.org/10.1021/acsnano.7b07473DOI Listing
January 2018

Planar n-Si/PEDOT:PSS hybrid heterojunction solar cells utilizing functionalized carbon nanoparticles synthesized via simple pyrolysis route.

Nanotechnology 2017 Nov;28(47):475402

Department of Materials and Chemical Engineering, Hanyang University, Ansan, Kyounggi 15588, Republic of Korea.

Herein, we present a facile and simple strategy for in situ synthesis of functionalized carbon nanoparticles (CNPs) via direct pyrolysis of ethylenediaminetetraacetic acid (EDTA) on silicon surface. The CNPs were incorporated in hybrid planar n-Si and poly(3,4-etyhlenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) solar cells to improve device performance. We demonstrate that the CNPs-incorporated devices showed increased electrical conductivity (reduced series resistance) and minority carrier lifetime (better charge carrier collection) than those of the cells without CNPs due to the existence of electrically conductive sp -hybridized carbon at the heterojunction interfaces. With an optimal concentration of CNPs, the hybrid solar cells exhibited power conversion efficiency up to 11.95%, with an open-circuit voltage of 614 mV, short-circuit current density of 26.34 mA cm, and fill factor of 73.93%. These results indicate that our approach is promising for the development of highly efficient organic-inorganic hybrid solar cells.
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http://dx.doi.org/10.1088/1361-6528/aa9014DOI Listing
November 2017

Highly active and durable carbon nitride fibers as metal-free bifunctional oxygen electrodes for flexible Zn-air batteries.

Nanoscale Horiz 2017 Nov 11;2(6):333-341. Epub 2017 Jul 11.

Department of Materials and Chemical Engineering, Hanyang University, Ansan, Kyunggido 426-791, Republic of Korea.

The design of flexible, highly energetic, and durable bifunctional oxygen electrocatalysts is indispensable for rechargeable metal-air batteries. Herein we present a simple approach for the development of carbon nitride fibers co-doped with phosphorus and sulfur, grown in situ on carbon cloth (PS-CNFs) as a flexible electrode material, and demonstrate its outstanding bifunctional catalytic activities toward ORR and OER compared to those of precious metal-based Pt/C and IrO on account of the dual action of P and S, numerous active sites, high surface area, and enhanced charge transfer. Furthermore, we demonstrate the flexibility, suitability, and durability of PS-CNFs as air electrodes for primary and rechargeable Zn-air batteries. Primary Zn-air batteries using this electrode showed high peak power density (231 mW cm), specific capacity (698 mA h g; analogous energy density of 785 W h kg), open circuit potential (1.49 V), and outstanding durability of more than 240 h of operation followed by mechanical recharging. Significantly, three-electrode rechargeable Zn-air batteries revealed a superior charge-discharge voltage polarization of ∼0.82 V at 20 mA cm, exceptional reversibility, and continuous charge-discharge cycling stability during 600 cycles. This work provides a pioneering strategy for designing flexible and stretchable metal-free bifunctional catalysts as gas diffusion layers for future portable and wearable renewable energy conversion and storage devices.
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http://dx.doi.org/10.1039/c7nh00058hDOI Listing
November 2017

Self-assembled air-stable magnesium hydride embedded in 3-D activated carbon for reversible hydrogen storage.

Nanoscale 2017 Jun;9(21):7094-7103

Department of Materials and Chemical Engineering, Hanyang University, Ansan, Kyunggido 426-791, Republic of Korea.

The rational design of stable, inexpensive catalysts with excellent hydrogen dynamics and sorption characteristics under realistic environments for reversible hydrogen storage remains a great challenge. Here, we present a simple and scalable strategy to fabricate a monodispersed, air-stable, magnesium hydride embedded in three-dimensional activated carbon with periodic synchronization of transition metals (MHCH). The high surface area, homogeneous distribution of MgH nanoparticles, excellent thermal stability, high energy density, steric confinement by carbon, and robust architecture of the catalyst resulted in a noticeable enhancement of the hydrogen storage performance. The resulting MHCH-5 exhibited outstanding hydrogen storage performance, better than that of most reported Mg-based hydrides, with a high storage density of 6.63 wt% H, a rapid kinetics loading in <5 min at 180 °C, superior reversibility, and excellent long-term cycling stability over ∼435 h. The significant reduction of the enthalpy and activation energy observed in the MHCH-5 demonstrated enhancement of the kinetics of de-/hydrogenation compared to that of commercial MgH. The origin of the intrinsic hydrogen thermodynamics was elucidated via solid state H NMR. This work presents a readily scaled-up strategy towards the design of realistic catalysts with superior functionality and stability for applications in reversible hydrogen storage, lithium ion batteries, and fuel cells.
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http://dx.doi.org/10.1039/c7nr01699aDOI Listing
June 2017

Scalable 3-D Carbon Nitride Sponge as an Efficient Metal-Free Bifunctional Oxygen Electrocatalyst for Rechargeable Zn-Air Batteries.

ACS Nano 2017 01 27;11(1):347-357. Epub 2016 Dec 27.

Department of Materials and Chemical Engineering, ‡Department of Bionano Technology, and §Department of Applied Chemistry, Hanyang University , Ansan, Kyunggido 426-791, Republic of Korea.

Rational design of efficient and durable bifunctional oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) electrocatalysts is critical for rechargeable metal-air batteries. Here, we developed a facile strategy for fabricating three-dimensional phosphorus and sulfur codoped carbon nitride sponges sandwiched with carbon nanocrystals (P,S-CNS). These materials exhibited high surface area and superior ORR and OER bifunctional catalytic activities than those of Pt/C and RuO, respectively, concerning its limiting current density and onset potential. Further, we tested the suitability and durability of P,S-CNS as the oxygen cathode for primary and rechargeable Zn-air batteries. The resulting primary Zn-air battery exhibited a high open-circuit voltage of 1.51 V, a high discharge peak power density of 198 mW cm, a specific capacity of 830 mA h g, and better durability for 210 h after mechanical recharging. An extraordinary small charge-discharge voltage polarization (∼0.80 V at 25 mA cm), superior reversibility, and stability exceeding prolonged charge-discharge cycles have been attained in rechargeable Zn-air batteries with a three-electrode system. The origin of the electrocatalytic activity of P,S-CNS was elucidated by density functional theory analysis for both oxygen reactions. This work stimulates an innovative prospect for the enrichment of rechargeable Zn-air battery viable for commercial applications such as armamentaria, smart electronics, and electric vehicles.
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http://dx.doi.org/10.1021/acsnano.6b05914DOI Listing
January 2017

Semi-continuous, real-time monitoring of protein biomarker using a recyclable surface plasmon resonance sensor.

Biosens Bioelectron 2017 Feb 12;88:232-239. Epub 2016 Aug 12.

Department of Bio-Microsystem Technology, Korea University, 145 Anam-ro, Seongbuk-Gu, Seoul 02841, Republic of Korea; Department of Biotechnology, Korea University, 2511 Sejong-ro, Sejong 30019, Republic of Korea. Electronic address:

Although label-free immunosensors based on, for example, surface plasmon resonance (SPR) provide advantages of real-time monitoring of the analyte concentration, its application to routine clinical analysis in a semi-continuous manner is problematic because of the high cost of the sensor chip. The sensor chip is in most cases regenerated by employing an acidic pH. However, this causes gradual deterioration of the activity of the capture antibody immobilized on the sensor surface. To use sensor chips repeatedly, we investigated a novel surface modification method that enables regeneration of the sensor surface under mild conditions. We introduced a monoclonal antibody (anti-CBP Ab) that detects the conformational change in calcium binding protein (CBP) upon Ca binding (>1mM). To construct a regenerable SPR-based immunosensor, anti-CBP Ab was first immobilized on the sensor surface, and CBP conjugated to the capture antibody (specific for creatine kinase-MB isoform (CK-MB); CBP-CAb) then bound in the presence of Ca. A serum sample was mixed with the detection antibody to CK-MB, which generated an SPR signal proportional to the analyte concentration. After each analysis, the sensor surface was regenerated using medium (pH 7) without Ca, and then adding fresh CBP-CAb in the presence of Ca for the subsequent analysis. Analysis of multiple samples using the same sensor was reproducible at a rate >98.7%. The dose-response curve was linear for 1.75-500.75ng/mL CK-MB, with an acceptable coefficient of variation of <8.8%. The performance of the immunosensor showed a strong correlation with that of the Pathfast reference system (R>96%), and exhibited analytical stability for 1 month. To our knowledge, this is the first report of a renewal of a sensor surface with fresh antibody after each analysis, providing high consistency in the assay during a long-term use (e.g., a month at least).
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http://dx.doi.org/10.1016/j.bios.2016.08.035DOI Listing
February 2017

Conformation-sensitive antibody-based point-of-care immunosensor for serum Ca(2+) using two-dimensional sequential binding reactions.

Biosens Bioelectron 2016 Nov 20;85:611-617. Epub 2016 May 20.

Department of Bio-Microsystem Technology, Korea University, 145 Anam-Ro, Sungbuk-Gu, Seoul 02841, Republic of Korea; Department of Biotechnology and Bioinformatics, Korea University, 2511 Sejong-Ro, Sejong 30019, Republic of Korea. Electronic address:

To assess the homeostasis of Ca(2+) metabolism, we have developed a rapid immunosensor for ionic calcium using a membrane chromatographic technique. As calcium-binding protein (CBP) is available for the recognition and undergone conformation change upon Ca(2+) binding, a monoclonal antibody sensitive to the altered structure of CBP has been employed. The sequential binding scheme was mathematically simulated and shown to match with the experimental results. At the initial stage, the rapid analytical system using lateral flow was constructed by immobilizing the antibody on the immuno-strip nitrocellulose membrane and labeling CBP with colloidal gold as a tracer. A major problem with this system in measuring ionic calcium levels was retarded migration of the gold tracer along the immuno-strip. It was conceivable that the divalent cation at a high concentration caused a change in the physical properties of the tracer, resulting in a non-specific interaction with the membrane surface. This problem was circumvented by first eluting a sample containing biotinylated CBP along the immuno-strip and then supplying the gold coupled to streptavidin across the signal generation pad of the strip. The color signal was then generated via biotin-SA linkage and measured using a smartphone-based detector developed in our laboratory. This two-dimensional chromatographic format completed the Ca(2+) analysis within 15min, the analytical performance covered the clinical dynamic range (0.25-2.5mM) and highly correlated with that of the reference system, i-STAT. These results inspired us to eventually investigate a dual-immunoassay system that measures simultaneously ionic calcium and parathyroid hormone, which regulates the ionic calcium level in serum. This will significantly simplify the current diagnostic protocols, which involve separate devices.
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http://dx.doi.org/10.1016/j.bios.2016.05.061DOI Listing
November 2016

Primary squamous cell carcinoma of the liver: a case report.

Clin Mol Hepatol 2016 Mar 28;22(1):177-82. Epub 2016 Mar 28.

Department of Internal Medicine, Kangbuk Samsung Hospital, Sungkyunkwan University School of Medicine, Seoul, Korea.

Primary squamous cell carcinoma (SCC) of the liver is very rare, and few cases have been reported in Korea. Primary SCC of the liver is known to be associated with hepatic cysts and intrahepatic stones. A 71-year-old male was admitted to our hospital, and a abdominal computed tomography scan revealed a 10 × 6 cm mass in the liver. Analysis of a biopsy sample suggested SCC, and so our team performed a thorough workup to find the primary lesion, which was revealed hepatoma as a pure primary SCC of the liver with multiple distant metastases. The patient was treated with one cycle of radiotherapy, transferred to another hospital for hospice care, and then died 1 month after discharge.
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http://dx.doi.org/10.3350/cmh.2016.22.1.177DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4825171PMC
March 2016

Chemiluminometric Immunosensor for High-Sensitivity Cardiac Troponin I Employing a Polymerized Enzyme Conjugate as a Tracer.

Sci Rep 2015 Oct 7;5:14848. Epub 2015 Oct 7.

Department of Bio-Microsystem Technology, Korea University, Sungbuk-gu, Seoul 136-701, Korea.

To detect high-sensitivity cardiac troponin I (hs-cTnI; <0.01 ng/mL) at points of care, we developed a rapid immunosensor by using horseradish peroxidase polymerized in 20 molecules on average (Poly-HRP) as a tracer conjugated with streptavidin (SA-Poly-HRP). As shown in the conventional system, enhanced sensitivity could be achieved by using a sequential binding scheme for the complex formation to contain the huge molecular tracer. We used a 2-dimensional chromatographic technology to carry out the sequential bindings in cross-flow directions. After the complex formation of antigen-antibody with analyte in a vertical direction, SA-Poly-HRP was horizontally supplied across the membrane strip for additional binding via a biotin-SA linkage. The HRP substrate was subsequently supplied along the same direction to produce a chemiluminometric signal, which was measured by a cooled charge-coupled device. Hs-cTnI analysis was completed in this format within 25 min, and the results showed a high correlation with those of the CentaurXP® reference system (R(2) > 0.99). The detection limit of the rapid immunosensor was 0.003 ± 0.001 ng/mL cTnI, corresponding to a 10-fold improvement compared to results using the plain enzyme tracer. This demonstrated the measurement of hs-cTnI in a much more cost-effective manner compared to the automated versions currently available.
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http://dx.doi.org/10.1038/srep14848DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4595837PMC
October 2015

Nanostructured SnS-N-doped graphene as an advanced electrocatalyst for the hydrogen evolution reaction.

Chem Commun (Camb) 2015 Nov 14;51(86):15716-9. Epub 2015 Sep 14.

Department of Materials and Chemical Engineering, Hanyang University, Ansan, Kyunggido 426-791, Republic of Korea.

The hydrogen evolution reaction (HER) via water splitting requires the development of advanced and inexpensive electrocatalysts to replace expensive platinum (Pt)-based catalysts. The scalable hydrothermal synthesis of SnS on N-reduced graphene (N-rGr) sheets is presented for the first time, which is used as a highly-active electrocatalyst with long-term stability in acidic, neutral, and alkaline media. This hybrid catalyst reveals a low overpotential of -125 mV, Tafel slope of 38 mV dec(-1), exchange current density of 6.23 mA cm(-2), onset potential of 59 mV, and long-term durability.
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http://dx.doi.org/10.1039/c5cc05644fDOI Listing
November 2015

Construction of an antimyoglobin single-chain variable fragment with rapid reaction kinetics.

Biotechnol Appl Biochem 2016 Jan-Feb;63(1):22-30. Epub 2015 Apr 28.

Department of Food and Biotechnology, Korea University, Sejong, Republic of Korea.

Antibodies with rapid reaction kinetics (high association and dissociation rates), named reversible antibodies, are used to perform continuous monitoring of sensitive disease biomarkers. In cases of acute myocardial infarction (AMI), continuous monitoring and early diagnosis are important. Human myoglobin (Myo) is a useful biomarker for AMI during the early stage after the onset of symptoms. In this study, a single-chain variable fragment (scFv) specific to Myo was derived from an IgG antibody that has rapid reaction kinetics. Enzyme-linked immunosorbent assay revealed that recombinant scFv exhibited 3.8-fold reduced affinity compared with the parent IgG antibody based on the antibody concentration necessary for 50% of the maximum signal. The scFv retained the rapid reaction kinetic mode with average kon and koff of 2.63 × 10(5) M(-1) Sec(-1) and 3.25 × 10(-3) Sec(-1) , respectively, which were reduced to 10- and 2.3-fold compared with those of the parent antibody. The equilibrium constant for the association of the scFv (KA = 8.09 × 10(7) M(-1) ) was 4.6-fold lower than that of its parent IgG antibody. This scFv may be a starting point for further mutagenesis/kinetic and structural analyses providing valuable insight into the mechanism of reversible antibodies.
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http://dx.doi.org/10.1002/bab.1349DOI Listing
October 2016

Purification and characterization of Fab fragments with rapid reaction kinetics against myoglobin.

Biosci Biotechnol Biochem 2015 3;79(5):718-24. Epub 2015 Jan 3.

a Functional Genomic Center , Korea Research Institute of Bioscience & Biotechnology , Daejeon , Republic of Korea.

Myoglobin is an early biomarker for acute myocardial infarction. Recently, we isolated the antibody IgG-Myo2-7ds, which exhibits unique rapid reaction kinetics toward human myoglobin antigen. Antibodies with rapid dissociation kinetics are thought to be premature IgG forms that are produced during the early stage of in vivo immunization. In the present study, we identified the epitope region of the IgG-Myo2-7ds antibody to be the C-terminal region of myoglobin, which corresponds to 144-154 aa. The Fab fragment was directly purified by papain cleavage and protein G affinity chromatography and demonstrated kinetics of an association constant of 4.02 × 10(4) M(-1) s(-1) and a dissociation constant of 2.28 × 10(-2) s(-1), which retained the unique reaction kinetics of intact IgG-Myo2-7ds antibodies. Because a rapid dissociation antibody can be utilized for antibody recycling, the results from this study would provide a platform for the development of antibody engineering in potential diagnostic areas such as a continuous monitoring system for heart disease.
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http://dx.doi.org/10.1080/09168451.2014.993354DOI Listing
May 2016

Refolded scFv antibody fragment against myoglobin shows rapid reaction kinetics.

Int J Mol Sci 2014 Dec 18;15(12):23658-71. Epub 2014 Dec 18.

Medical Proteomics Research Center, Korea Research Institute of Bioscience & Biotechnology, Daejeon 305-806, Korea.

Myoglobin is one of the early biomarkers for acute myocardial infarction. Recently, we have screened an antibody with unique rapid reaction kinetics toward human myoglobin antigen. Antibodies with rapid reaction kinetics are thought to be an early IgG form produced during early stage of in vivo immunization. We produced a recombinant scFv fragment for the premature antibody from Escherichia coli using refolding technology. The scFv gene was constructed by connection of the V(H)-V(L) sequence with a (Gly4Ser)3 linker. The scFv fragment without the pelB leader sequence was expressed at a high level, but the solubility was extremely low. A high concentration of 8 M urea was used for denaturation. The dilution refolding process in the presence of arginine and the redox reagents GSH and GSSH successfully produced a soluble scFv protein. The resultant refolded scFv protein showed association and dissociation values of 9.32 × 10⁻⁴ M⁻¹·s⁻¹ and 6.29 × 10⁻³ s⁻¹, respectively, with an affinity value exceeding 10⁷ M⁻¹ (k(on)/k(off)), maintaining the original rapid reaction kinetics of the premature antibody. The refolded scFv could provide a platform for protein engineering for the clinical application for diagnosis of heart disease and the development of a continuous biosensor.
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http://dx.doi.org/10.3390/ijms151223658DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4284786PMC
December 2014

Continuous immunosensing of myoglobin in human serum as potential companion diagnostics technique.

Biosens Bioelectron 2014 Dec 24;62:234-41. Epub 2014 Jun 24.

Department of Bio-Microsystem Technology, Korea University, 1, 5-ka, Anam-dong, Seongbuk-Gu, Seoul 136-701, Republic of Korea; Department of Biotechnology and Bioinformatics, Korea University, 2511 Sejong-ro, Sejong 339-700, Republic of Korea. Electronic address:

To attain early diagnosis of acute myocardial infarction (AMI) with enhanced accuracy, continuous immunosensing has been investigated to measure myoglobin concentration in real-time. To this end, a capture antibody showing rapid reaction kinetics was immobilized on the surface of a surface plasmon resonance sensor. Three problems associated with the continuous sensing of myoglobin in human serum needed to be overcome: non-specific binding of the analyte, aggregation of serum components, and drift of the sensor baseline. Non-specific binding was controlled by pretreating the sample with a detergent mixture consisting of sodium dodecyl sulfate and P20, and adjusting the micelle size and net charge. Aggregation was managed by inactivating certain serum constituents through chelation of heavy metals. Baseline drift perceived in the sensorgram was able to be corrected by compensating for the slope calculated by a linear regression. Under the optimal conditions, the continuous sensor reproducibly traced the varying doses of myoglobin over about 8h with periodic one-point calibration every 3h. The dose-response curve of the sensor was linear with acceptable variations (CVs<4.91% in average) between the detection limit (31.0 ng/mL) and about 2000 ng/mL in the arithmetic scale (R(2)>0.98), covering the clinical concentration range. The immunosensor performance correlated with the Pathfast reference system (R(2)>0.98) and analytical consistency could be maintained for longer than a month if appropriately calibrated. Such immunosensing could be used as a companion diagnostic means along with real-time electrocardiographic measurement, significantly enhancing the sensitivity of AMI diagnosis and thereby enabling treatment at an early stage.
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http://dx.doi.org/10.1016/j.bios.2014.06.039DOI Listing
December 2014

Semi-continuous, label-free immunosensing approach for Ca2+-based conformation change of a calcium-binding protein.

Analyst 2014 Aug;139(15):3781-9

Department of Bio-Microsystem Technology, Korea University, 1, 5-ka, Anam-dong, Sungbuk-gu, Seoul 136-701, Korea.

A label-free immunosensing method based on the conformational change of calcium-binding protein (CBP) depending on analyte concentration was explored for semi-continuous analysis of free Ca(2+). Glucose-galactose-binding protein as a CBP and produced as a recombinant protein by Escherichia coli was used as the immunogen to produce monoclonal antibodies by hybridoma technology. We finally screened the 3-6F cell clone, which produced the desired antibody specific to a particular structural conformation of the protein that occurred only upon CBP-calcium complex formation. To construct an immunosensor, the antibody was immobilized via a secondary antibody on an Octet Red optical fiber-based label-free sensor. Calcium analysis was conducted on the sensor in combination with CBP previously added to the aqueous sample, which distinguished the sensor signal according to the analyte concentration. The immunosensor produced a signal in real time with a response time of approximately 15 min and could be reused for analyses of different samples in a semi-continuous manner. The minimum detection limit of the analyte under optimal conditions was 0.09 mM and the upper limit was about 5 mM (log-logit transformed standard curve linearity: R(2) > 98%). In sample tests with milk, the analytical performance of the sensor was highly correlated (R(2) > 99%) with that of the reference system based on the KMnO4 titration method (ISO 12081). Although the sensor showed cross-reactivity at high concentrations (>1 mM) of cations including zinc, iron, manganese, and copper, these ionic components were not traceable (<0.01 mM) in milk.
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http://dx.doi.org/10.1039/c4an00343hDOI Listing
August 2014

Toll-like receptor-based immuno-analysis of pathogenic microorganisms.

Anal Chem 2012 Nov 9;84(22):9713-20. Epub 2012 Nov 9.

Program for Bio-Microsystem Technology, 1, 5-ka, Anam-dong, Seongbuk-Gu, Seoul 136-701, Korea.

In this study, a novel mammalian cell receptor-based immuno-analytical method was developed for the detection of food-poisoning microorganisms by employing toll-like receptors (TLRs) as sensing elements. Upon infection with bacterium, the host cells respond by expressing TLRs, particularly TLR1, TLR2, and TLR4, on the outer membrane surfaces. To demonstrate the potential of using this method for detection of foodborne bacteria, we initially selected two model sensing systems, expression of TLR1 on a cell line, A549, for Escherichia coli and TLR2 on a cell line, RAW264.7, for Shigella sonnei (S. sonnei). Each TLR was detected using antibodies specific to the respective marker. We also found that the addition of immunoassay for the pathogen captured by the TLRs on the mammalian cells significantly enhanced the detection capability. A dual-analytical system for S. sonnei was constructed and successfully detected an extremely low number (about 3.2 CFU per well) of the pathogenic bacterium 5.1 h after infection. This detection time was 2.5 h earlier than the time required for detection using the conventional immunoassay. To endow the specificity of detection, the target bacterium was immuno-magnetically concentrated by a factor of 50 prior to infection. This further shortened the response to approximately 3.4 h, which was less than half of the time needed when the conventional method was used. Such enhanced performance could basically result from synergistic effects of bacterial dose increase and subsequent autocrine signaling on TLRs' up-regulation upon infection with live bacterium. This TLR-based immuno-sensing approach may also be expanded to monitor infection of the body, provided scanning of the signal is feasible.
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http://dx.doi.org/10.1021/ac300668yDOI Listing
November 2012

Performance characteristics of monoclonal antibodies as recyclable binders to cardiac troponin I.

Anal Biochem 2012 Dec 8;431(1):11-8. Epub 2012 Sep 8.

Department of Bio-Microsystem Technology, Korea University, Sungbuk-gu, Seoul 136-701, Republic of Korea.

Acute myocardial infarction is a typical disorder that requires continuous monitoring for early detection of potential life-threatening situations. To this end, we used different methods to screen for rapidly reversible antibodies, among 22 hybridoma clones, against cardiac troponin I (cTnI), which is a specific marker indicating the disease. The dissociation rates of antibodies were underestimated by up to a factor of 1000 because of bivalent binding when tested with the antigen immobilized on solid surfaces. This effect was also observed in a sandwich immunoassay, in which the detection antibody cross-linked with various antigen molecules already bound to the capture antibody. Although multiple binding events contributed to enhanced detection capability, it was difficult to recycle the immunosensor. We then devised a screening system by arranging the test antibody for the capture binder immobilized on a label-free sensor. This enabled us to select fast reactive antibodies of which one (clone 24) was shown to be recyclable, even in serum-containing medium. Using this antibody, repetitive detection of cTnI with a rapid response time (half-life of dissociation: about 4min on average) and high detection capability (0.1ng/ml) was achieved, which is very important for detection in a clinical setting.
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http://dx.doi.org/10.1016/j.ab.2012.09.002DOI Listing
December 2012

Label-free, needle-type biosensor for continuous glucose monitoring based on competitive binding.

Biosens Bioelectron 2013 Feb 7;40(1):38-44. Epub 2012 Jun 7.

Department of Bio-Microsystem Technology, Korea University, 1, 5-ka, Anam-dong, Seongbuk-gu, Seoul 136-701, Republic of Korea.

With the goal of developing a method for the continuous monitoring of blood glucose, an implantable sensor was developed by placing an optical fiber probe within the internal hollow space of a syringe needle. A glucose binder, concanavalin A (Con A), was immobilized on the probe tip and a protein (e.g., bovine serum albumin) chemically coupled with a sugar ligand (e.g., mannose) was loaded as a solution inside of the needle, which were then closed using a semi-permeable membrane. Upon immersion in the glucose sample, small molecules were able to freely pass through the membrane and compete with the ligand conjugate for Con A binding. This changed the molecular layer thickness on the probe surfaces depending on the glucose concentration, which shifted the wavelength of the guided light along the fiber. Such interference in the wavelength pattern was measured using a commercial sensor system, Octet, without employing a label. Using this analytical approach, two major steps controlling the performance of glucose detection were overcome: permeation of glucose (optimum with 50 nm-porous polycarbonate membrane under the experimental conditioned used) and molecular diffusion of the ligand conjugate within the sensor compartment (19 gauge-needle, offering minimal demensions for the probe). Under optimal conditions, the sensor was able to monitor glucose fluctuations, even in serum medium, with a response time of less than 15 min in a range 10-500 mg/dL. This, however, could be further shortened down to about 5 min in principle by miniaturizing the sensor dimensions.
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http://dx.doi.org/10.1016/j.bios.2012.05.038DOI Listing
February 2013

Premature antibodies with rapid reaction kinetics and their characterization for diagnostic applications.

Anal Biochem 2012 Jan 14;420(1):54-60. Epub 2011 Sep 14.

Department of Bio-Microsystem Technology, Korea University, Sungbuk-gu, Seoul 136-701, Republic of Korea.

In this study, rapidly reversible antibodies were produced and the binding kinetics, stability, and utility as an analytical binder were evaluated. The number of times the animals were immunized with the antigen (myoglobin as marker for acute myocardial infarction [AMI]) was limited to two, increasing the chances of producing premature antibodies that rapidly reacted with the binding partner in both association and dissociation. The rate constants were higher than 1×10(6)M(-1)s(-1) and 1×10(-3)s(-1), respectively, and the affinity exceeded 10(8)M(-1). They responded to an abrupt environmental change (acidic pH in this study) where the reaction kinetics was changed to slow binding, particularly for dissociation, resulting in a 10-fold increase in affinity. The binding characteristic before and after the transition were stable at 37°C for longer than 1 month, suggesting that the rapidly reversible antibody was the intermediate of the slow binder. The rapid kinetic antibody was used as the primary binder in the conventional competitive immunoassay, which displayed a lower sensitivity than the transformed antibody due to its lower affinity. We further demonstrated that, on combination with a microfluidic label-free sensor, the reaction could be continuously monitored in serum medium by recycling the same antibody without employing the regeneration step.
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http://dx.doi.org/10.1016/j.ab.2011.09.006DOI Listing
January 2012
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