• 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 KIEE Conference
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• 2006.07c
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• pp.1647-1648
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• 2006

화학적, 생물학적 분석, 즉 특정 물질의 존재 유무를 측정하기 위해 마이크로캔틸레버라는 구조체를 제작하여 이를 바이오센서로 응용하였다. 마이크로캔틸레버의 장점은 분석하고자 하는 시료의 양이 적더라도 감지가 가능하고 이를 통하여 분석시간을 단축할 수 있다는 장점을 가지고 있다. 마이크로캔틸레버 구조물 제작을 위해 보편적으로 많이 이용되는 bulk 미세 가공 기술을 대신하여 표면 미세 가공기술을 이용하였다. 이러한 표면 미세 가공기술은 bulk 미세 가공기술에 비해 공정이 간단하고 값이 싸다는 장점이 있다. 또 액상 실험을 위하여 polydimethylsiloxane (PDMS)와 fused silica glass를 사용한 유체 제어 시스템을 제작하였다. 본 연구에서는 자기조림 이라는 특성을 이용하여 생물분자를 유체 제어 시스템 내의 마이크로캔틸레버 상단에 immobilization 시킨 후 마이크로캔틸레버 상, 하단의 표면 스트레스 차이에 따른 마이크로캔틸레버 자체의 휘어지는 정도를 측정하였다. 이러한 휘어지는 현상을 관찰함으로서 마이크로캔틸레버의 바이오센서로 응용 가능성을 확인한 수 있었다.

• Analytical Science and Technology
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• v.29 no.1
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• pp.35-42
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• 2016

A new nano-composite carbon ink for the development of disposable dopamine (DA) biosensors based on screen-printed carbon electrodes (SPCEs) is introduced. The method developed uses SPCEs coupled with a tyrosinase modified nano-composite carbon ink. The ink was prepared by an “in-house” procedure with reduced graphene oxide (rGO), Pt nanoparticles (PtNP), and carbon materials such as carbon black and graphite. The rGO-PtNP carbon composite ink was used to print the working electrodes of the SPCEs and the reference counter electrodes were printed by using a commercial Ag/AgCl ink. After the construction of nano-composite SPCEs, tyrosinase was immobilized onto the working electrodes by using a biocompatible matrix, chitosan. The composite of nano-materials was characterized by X-ray photoelectron spectroscopy (XPS) and the performance characteristics of the sensors were evaluated by using voltammetric and amperometric techniques. The cyclic voltammetry results indicated that the sensors prepared with the rGO-PtNP-carbon composite ink revealed a significant improvement in electro-catalytic activity to DA compared with the results obtained from bare or only PtNP embedded carbon inks. Optimum experimental parameters such as pH and operating potential were evaluated and calibration curves for dopamine were constructed with the results obtained from a series of amperometric detections at −0.1 V vs. Ag/AgCl. The limit of detection was found to be 14 nM in a linear range of 10 nM to 100 µM of DA, and the sensor’s sensitivity was calculated to be 0.4 µAµM⁻¹cm⁻².

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.431-431
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• 2011

Graphene, two dimensional sheet of sp2-hybridized carbon, has attracted an enormous amount of interest due to excellent electrical, chemical and mechanical properties for the application of transparent conducting films, clean energy devices, field-effect transistors, optoelectronic devices and chemical sensors. Especially, graphene is promising candidate to detect the gas molecules and biomolecules due to the large specific surface area and signal-to-noise ratios. Despite of importance to the disease diagnosis, there are a few reports to demonstrate the graphene- and rGO-FET for biological sensors and the sensing mechanism are not fully understood. Here we describe scalable and facile fabrication of rGO-FET with the capability of label-free, ultrasensitive electrical detection of a cancer biomarker, prostate specific antigen/${\alpha}1$-antichymotrypsin (PSA-ACT) complex, in which the ultrathin rGO sensing channel was simply formed by a uniform self-assembly of two-dimensional rGO nanosheets on aminated pattern generated by inkjet printing. Sensing characteristics of rGO-FET immunosensor showed the highly precise, reliable, and linear shift in the Dirac point with the analyte concentration of PSA-ACT complex and extremely low detection limit as low as 1 fg/ml. We further analyzed the charge doping mechanism, which is the change in the charge carrier in the rGO channel varying by the concentration of biomolecules. Amenability of solution-based scalable fabrication and extremely high performance may enable rGO-FET device as a versatile multiplexed diagnostic biosensor for disease biomarkers.

• Journal of Sensor Science and Technology
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• v.22 no.3
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• pp.185-190
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• 2013

We report on direct finding of how the morphology (i.e. filopodia width) of $CD4^+$ T lymphocytes correlates with the size of the quartz nanohohole arrays (QNHAs, 140, 200, 270, and 550 nm in diameter) via scanning electron microscopy (SEM). This research exhibits that the filopodia of $CD4^+$ T-lymphocytes extended on the QNHA substrates were observed to increase in width by increasing the size of QNHA in diameter from 140 to 550 nm. This strong linear response ($R^2$=0.988, n = 6) in filopodia's width of surface-bound $CD4^+$ T-cells with topographical structures of QNHA can be explained by contact guidance between the cells and solid-state substrates. Furthermore, this research suggests that the protruded filopodia of surface-bound T-lymphocytes can be used as a biosensor for sensing the topographical information of the nano-patterned substrates.

• Journal of Microbiology and Biotechnology
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• v.17 no.7
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• pp.1191-1197
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• 2007

The detection and kinetics of mucosal pathogenic bacteria binding on polysaccharide ligands were studied using a surface plasmon resonance biosensor. The kinetic model applied curve-fitting to the experimental surface plasmon resonance sensorgrams to evaluate the binding interactions. The kinetic parameters for the mucosal pathogenic bacteria (Pseudomonas aeruginosa, Pseudomonas fluorescens, Serratia marcescens) with the alginate ligand were determined from a kinetic model. In addition, the binding interactions of the mucosal pathogenic bacteria with polysaccharide binding pairs (Pseudomonas aeruginosa/alginate, Streptococcus pneumoniae/pneumococcal polysaccharide, Staphylococcus aureus/pectin) were also compared with their kinetic parameters. The rate constants of association for Pseudomonas aeruginosa with the alginate ligand were higher than those for Pseudomonas fluorescens. Serratia marcescens had no detectable interaction with the alginate ligand. The adhesion affinity of Pseudomonas aeruginosa with alginate was higher than that for the other binding pairs. The binding affinities of the pathogenic bacteria with their own polysaccharide were higher than that of Staphylococcus aureus with pectin. Measuring the contact angle was found to be a feasible method for detecting binding interactions between analytes and ligands.

• JSTS:Journal of Semiconductor Technology and Science
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• v.14 no.2
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• pp.153-162
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• 2014

We show that carbon nanotube sensors with gold particles on the single-walled carbon nanotube (SWNT) network operate as Schottky barrier transistors, in which transistor action occurs primarily by varying the resistance of Au-SWNT junction rather than the channel conductance modulation. Transistor characteristics are calculated for the statistically simplified geometries, and the sensing mechanisms are analyzed by comparing the simulation results of the MOSFET model and Schottky junction model with the experimental data. We demonstrated that the semiconductor MOSFET effect cannot explain the experimental phenomena such as the very low limit of detection (LOD) and the logarithmic dependence of sensitivity to the DNA concentration. By building an asymmetric concentric-electrode model which consists of serially-connected segments of CNTFETs and Schottky diodes, we found that for a proper explanation of the experimental data, the work function shifts should be ~ 0.1 eV for 100 pM DNA concentration and ~ 0.4 eV for $100{\mu}M$.

• BioChip Journal
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• v.12 no.4
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• pp.268-279
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• 2018

Flower-shaped organic-inorganic hybrid nanostructures, termed nanoflowers, have received considerable recent attention as they possess greatly enhanced activity, stability, durability, and even selectivity of entrapped organic biomolecules, which are much better than those from the conventional methods. They can be synthesized simply via co-incubation of organic and inorganic components in aqueous buffer at room temperature and yield hierarchical nanostructures with large surface-to-volume ratios, allowing for low-cost production by easy scale-up, as well as the high loading capacity of biomolecules without severe mass transfer limitations. Since a pioneering study reported on hybrid nanoflowers prepared with protein and copper sulfate, many other organic and inorganic components, which endow nanoflowers with diverse functionalities, have been employed. Thanks to these features, they have been applied in a diverse range of areas, including biosensors and biocatalysis. To highlight the progress of research on organic-inorganic hybrid nanoflowers, this review discusses their synthetic methods and mechanisms, structural and biological characteristics, as well as recent representative applications. Current challenges and future directions toward the design and development of multi-functional nanoflowers for their widespread utilization in biotechnology are also discussed.

• Bulletin of the Korean Chemical Society
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• v.35 no.9
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• pp.2749-2752
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• 2014

Recent studies have shown that single-stranded DNA adsorbed onto graphene oxide is protected from DNase I cleavage. However, double-stranded DNA bound to graphene oxide and could be digested by DNase I. To elucidate whether single-stranded DNA is protect from DNase I in the presence of graphene oxide, this study conducted DNase I digestion using single-stranded DNA and single-stranded DNA containing the duplex region in the presence of graphene oxide. Addition of DNase I resulted in restoration of the fluorescence emission that had been quenched when DNA was adsorbed to graphene oxide. It indicates that DNase I cleaved the adsorbed single-stranded DNA onto graphene oxide, which was sufficient for the detection of DNase I activity.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.83-83
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• 2013

To date, various nanobiotechnologicalapproaches for biosensors and drug development have been explosively studied. Despite of successful demonstrations, the new technologies hardly enjoyed routine applications in practical nanobiomedicine. Here, researchers trained at the interface of basic sciences and engineering are expected to play critical roles. In this tutorial, I will introduce recent studies which harness graphene derivatives for developing bioanalytical platforms to quantitatively analyze various enzyme activities and biomarkers. The systems rely on attractive interaction between graphene oxide and nucleic acids or phospholipids. Recently, one of the graphene-based bioassay system was applied to anti-viral drug screening and potent hit compounds were identified to treat hepatitis C. This study clearly shows that a new nanobio-technology can be routinely implemented in drug discovery, providing many advantages over conventional methods.