Microfludic 플랫폼을 이용한 생체 분자의 voltammetric 분석

Rohit Chand,한다운(Dawoon Han),Sandeep K. Jha,김용상(Yong-Sang Kim) 대한전기학회 2011 대한전기학회 학술대회 논문집 Vol.2011 No.7

Voltammetric Analysis on a Disposable Microfluidic Electrochemical Cell

Rohit Chand,한다운,김용상 대한화학회 2013 Bulletin of the Korean Chemical Society Vol.34 No.4

A microfabricated electrochemical cell comprising PDMS-based microchannel and in-channel gold microelectrodes was fabricated as a sensitive and a miniature alternative to the conventional electroanalytical systems. A reproducible fabrication procedure enabled patterning of multiple microelectrodes integrated within a PDMS-based fluidic network. The active area of each electrode was 200 μm × 200 μm with a gap of 200 μm between the electrodes which resulted in a higher signal to noise ratio. Also, the PDMS layer served the purpose of shielding the electrical interferences to the measurements. Analytes such as potassium ferrocyanide; amino acid: cysteine and nucleoside: guanosine were characterized using the fabricated cell. The microchip was comparable to bulk electrochemical systems and its applicability was also demonstrated with flow injection based rapid amperometric detection of DNA samples. The device so developed shall find use as a disposable electrochemical cell for rapid and sensitive analysis of electroactive species in various industrial and research applications.

Detection of protein kinase using an aptamer on a microchip integrated electrolyte-insulator-semiconductor sensor

Chand, Rohit,Han, Dawoon,Neethirajan, Suresh,Kim, Yong-Sang Elsevier 2017 Sensors and actuators. B Chemical Vol.248 No.-

<P><B>Abstract</B></P> <P>Herein, we developed a microchip electrolyte-insulator-semiconductor (EIS) sensor for the capacitive detection of protein kinase A (PKA). EIS sensing is customarily performed in a Teflon cell to define the sensing area. However, in this work, a rapid prototyping technique was followed to integrate polymeric microchip, a reference electrode, and the EIS sensor. The aptameric peptide was used for one-step and label-free detection of PKA enzyme. The thiolated PKA-specific aptamer was immobilized on the gold nanoparticles decorated EIS sensor surface. The detection of PKA in microchip was based on the change in surface charge of EIS sensor. We also analyzed the ability of microchip-EIS sensor to distinguish between buffers at different pH. An average sensitivity of 96mV/pH for a pH range of 5–9 was obtained. The quantitative detection of PKA was performed by analyzing the capacitance-voltage curve after the aptamer-PKA interaction. The EIS sensor showed a detection limit of 2U/mL with a relative linearity from 10U/mL to 80U/mL for the detection of PKA. This study proposes an integrated and point-of-care applicable biosensor for the rapid diagnosis.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The EIS sensor integrated with microchip and reference electrode was fabricated. </LI> <LI> The microchip-EIS was used for detection of protein kinase. </LI> <LI> The change in surface charge alters the V<SUB>G</SUB> of EIS sensor. </LI> <LI> PKA was efficiently detected on-chip using aptamer. </LI> <LI> The microchip-EIS was highly specific, selective and stable. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Voltammetric Analysis on a Disposable Microfluidic Electrochemical Cell

Chand, Rohit,Han, Dawoon,Kim, Yong-Sang Korean Chemical Society 2013 Bulletin of the Korean Chemical Society Vol.34 No.4

A microfabricated electrochemical cell comprising PDMS-based microchannel and in-channel gold microelectrodes was fabricated as a sensitive and a miniature alternative to the conventional electroanalytical systems. A reproducible fabrication procedure enabled patterning of multiple microelectrodes integrated within a PDMS-based fluidic network. The active area of each electrode was $200{\mu}m{\times}200{\mu}m$ with a gap of $200{\mu}m$ between the electrodes which resulted in a higher signal to noise ratio. Also, the PDMS layer served the purpose of shielding the electrical interferences to the measurements. Analytes such as potassium ferrocyanide; amino acid: cysteine and nucleoside: guanosine were characterized using the fabricated cell. The microchip was comparable to bulk electrochemical systems and its applicability was also demonstrated with flow injection based rapid amperometric detection of DNA samples. The device so developed shall find use as a disposable electrochemical cell for rapid and sensitive analysis of electroactive species in various industrial and research applications.

Electroimmobilization of DNA for ultrafast detection on a microchannel integrated pentacene TFT

Rohit Chand,전준호,박민호,김정민,신익수,김용상 한국공업화학회 2015 Journal of Industrial and Engineering Chemistry Vol.21 No.1

We report a pentacene thin-film transistor integrated with microfluidic channel as an ultrafast DNAsensor. The microchannel assisted in easy transport of sample onto the pentacene active layer. The DNAimmobilization time on active layer was drastically shortened by applying low positive electric field atthe gate electrode. This helps by attracting the negatively charged DNA toward the pentacene layer. Thisdevice was evaluated for the label-free detection of single stranded DNA. The electrical property of thedevice fiercely changed due to the adsorption of DNA. Furthermore, the electrical characteristics werestudied as a function of immobilization voltage and time

Electroimmobilization of DNA for ultrafast detection on a microchannel integrated pentacene TFT

Chand, Rohit,Jeun, Jun-Ho,Park, Min-Ho,Kim, Jung-Min,Shin, Ik-Soo,Kim, Yong-Sang Elsevier 2015 Journal of industrial and engineering chemistry Vol.21 No.-

<P><B>Abstract</B></P> <P>We report a pentacene thin-film transistor integrated with microfluidic channel as an ultrafast DNA sensor. The microchannel assisted in easy transport of sample onto the pentacene active layer. The DNA immobilization time on active layer was drastically shortened by applying low positive electric field at the gate electrode. This helps by attracting the negatively charged DNA toward the pentacene layer. This device was evaluated for the label-free detection of single stranded DNA. The electrical property of the device fiercely changed due to the adsorption of DNA. Furthermore, the electrical characteristics were studied as a function of immobilization voltage and time.</P>

Gold Nanoparticle Enhanced Electrochemical Assay for Protein Kinase Activity Using a Synthetic Chemosensor on a Microchip

Chand, Rohit,Han, Dawoon,Shin, Ik-Soo,Hong, Jong-In,Kim, Yong-Sang The Electrochemical Society 2015 Journal of the Electrochemical Society Vol.162 No.4

<P>Phosphorylation by protein kinases is a predominant form of protein regulation. Abnormal phosphorylation of protein is linked to several medical conditions. In this paper, we report a disposable electrochemical microchip for protein kinase activity assay based on a synthetic chemosensor. The approach involves the phosphate-specific chemosensors linked to gold nanoparticles, anchored on an electrochemical sensor fabricated on the plastic film, and the enzyme substrate labeled with ferrocene tag. In the presence of protein kinase, the substrate undergoes phosphorylation, which subsequently binds to the chemosensor, and then the ferrocene tag of the enzymatic product generates strong oxidation current under voltammetry. Gold nanoparticles were employed as a bridge between the electrode and chemosensor, which significantly enhanced the current signal. A limit of detection of the enzyme was estimated to be 0.05 U/mL with a linear dynamic range between 2–50 U/mL. Furthermore, the interference and inhibition studies were also successfully carried out using this strategy. The method proposes the potential for application in the development of a kinase assay system.</P>

An Electrochemical Assay for Restriction Endonuclease Activity Using Graphene Monolayer

Islam, Kamrul,Chand, Rohit,Han, Dawoon,Shin, Ik-Soo,Kim, Yong-Sang The Electrochemical Society 2014 Journal of the Electrochemical Society Vol.161 No.12

<P>Herein, we report a new electrochemical assay for the endonuclease activity using a graphene monolayer. The approach involves a methylene blue (MB) tagged double-stranded (ds) DNA as an enzyme substrate with a single-stranded (ss) segment at the end for anchoring on graphene through π-π stacking. The nuclease enzyme mediates DNA hydrolysis following the release of dsDNA-MB from the graphene surface, which reduces the electrochemical current signal. The protocol was validated for the HaeIII and EcoRV restriction endonuclease enzyme. We also assayed the activity of methyltransferase enzyme and inhibition of restriction by HaeIII. The method allows real-time measurement and quantitative assay for endonuclease activities in a simple manner.</P>

Microscale loop-mediated isothermal amplification of viral DNA with real-time monitoring on solution-gated graphene FET microchip

Han, Dawoon,Chand, Rohit,Kim, Yong-Sang Elsevier 2017 Biosensors & bioelectronics Vol.93 No.-

<P><B>Abstract</B></P> <P>Rapid and reliable molecular analysis of DNA for disease diagnosis is highly sought-after. FET-based sensors fulfill the demands of future point-of-care devices due to its sensitive charge sensing and possibility of integration with electronic instruments. However, most of the FETs are unstable in aqueous conditions, less sensitive and requires conventional Ag/AgCl electrode for gating. In this work, we propose a solution-gated graphene FET (SG-FET) for real-time monitoring of microscale loop-mediated isothermal amplification of DNA. The SG-FET was fabricated effortlessly with graphene as an active layer, on-chip co-planar electrodes, and polydimethylsiloxane-based microfluidic reservoir. A linear response of about 0.23V/pH was seen when the buffers from pH 5–9 were analyzed on the SG-FET. To evaluate the performance of SG-FET, we monitored the amplification of Lambda phage gene as a proof-of-concept. During amplification, protons are released, which gradually alters the Dirac point voltage (V<SUB>Dirac</SUB>) of SG-FET. The resulting device was highly sensitive with a femto-level limit of detection. The SG-FET could easily produce a positive signal within 16.5min of amplification. An amplification of 10ng/μl DNA for 1h produced a ∆V<SUB>Dirac</SUB> of 0.27V. The sensor was tested within a range of 2×10<SUP>2</SUP> copies/μl (10 fg/μl) to 2×10<SUP>8</SUP> copies/μl (10ng/μl) of target DNA. Development of this sensing technology could significantly lower the time, cost, and complications of DNA detection.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The solution-gated graphene FET (SG-FET) integrated with microchannel was fabricated. </LI> <LI> The SG-FET was used for real-time monitoring of loop-mediated isothermal amplification of DNA. </LI> <LI> Proton released during the LAMP alters the V<SUB>Dirac</SUB> of SG-FET. </LI> <LI> Viral DNA was efficiently amplified on-chip and monitored. </LI> <LI> SG-FET could analyze 10 fg/μl of DNA in just 5μl of reaction mixture. </LI> </UL> </P>

Homogeneous Electrochemical Assay for Protein Kinase Activity

Shin, Ik-Soo,Chand, Rohit,Lee, Sang Wook,Rhee, Hyun-Woo,Kim, Yong-Sang,Hong, Jong-In American Chemical Society 2014 ANALYTICAL CHEMISTRY - Vol.86 No.22

<P>Herein, we report a homogeneous assay for protein kinase activity using an electrochemistry-based probe. The approach involves a peptide substrate conjugated with a redox tag and the phosphate-specific receptor immobilized on an electrode surface. The peptide substrate phosphorylated by a protein kinase binds to the receptor site of the probe, which results in a redox current under voltammetric measurement. Our method was successfully applied even in the presence of citrated human blood and modified to enable a single-use, chip-based electrochemical assay for kinase activity.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancham/2014/ancham.2014.86.issue-22/ac502549s/production/images/medium/ac-2014-02549s_0005.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ac502549s'>ACS Electronic Supporting Info</A></P>