Publications by authors named "Warakorn Limbut"

26 Publications

  • Page 1 of 1

Discrimination of dopamine by an electrode modified with negatively charged manganese dioxide nanoparticles decorated on a poly(3,4 ethylenedioxythiophene)/reduced graphene oxide composite.

J Colloid Interface Sci 2021 Mar 31;597:314-324. Epub 2021 Mar 31.

Center of Excellence for Trace Analysis and Biosensor, Prince of Songkla University, Hat Yai, Songkhla 90112, Thailand; Center of Excellence for Innovation in Chemistry, Faculty of Science, Prince of Songkla University, HatYai, Songkhla 90112, Thailand; Division of Health and Applied Sciences, Faculty of Science, Prince of Songkla University, Hat Yai, Songkhla 90112, Thailand. Electronic address:

A unique nanocomposite was fabricated using negatively charged manganese dioxide nanoparticles, poly (3,4-ethylenedioxythiophene) and reduced graphene oxide (MnO/PEDOT/rGO). The nanocomposite was deposited on a glassy carbon electrode (GCE) functionalized with amino groups. The modified GCE was used to electrochemically detect dopamine (DA). The surface morphology, charge effect and electrochemical behaviours of the modified GCE were characterized by scanning electron microscopy, energy dispersive X-ray analysis (EDX), cyclic voltammetry and electrochemical impedance spectroscopy, respectively. The MnO/PEDOT/rGO/GCE exhibited excellent performance towards DA sensing with a linear range between 0.05 and 135 µM with a lowest detection limit of 30 nM (S/N = 3). Selectivity towards DA was high in the presence of high concentrations of the typical interferences ascorbic acid and uric acid. The stability and reproducibility of the electrode were good. The sensor accurately determined DA in human serum. The synergic effect of the multiple components of the fabricated nanocomposite were critical to the good DA sensing performance. rGO provided a conductive backbone, PEDOT directed the uniform growth of MnO and adsorbed DA via pi-pi and electrostatic interaction, while the negatively charged MnO provided adsorption and catalytic sites for protonated DA. This work produced a promising biosensor that sensitively and selectively detected DA.
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http://dx.doi.org/10.1016/j.jcis.2021.03.162DOI Listing
March 2021

A portable electrochemical sensor for detection of the veterinary drug xylazine in beverage samples.

J Pharm Biomed Anal 2021 May 8;198:113958. Epub 2021 Feb 8.

Center of Excellence for Trace Analysis and Biosensors (TAB-CoE), Prince of Songkla University, Hat Yai, Songkhla, 90112, Thailand; Center of Excellence for Innovation in Chemistry, Faculty of Science, Prince of Songkla University, Hat Yai, Songkhla, 90112, Thailand; Division of Health and Applied Sciences, Faculty of Science, Prince of Songkla University, Hat Yai, Songkhla, 90112, Thailand. Electronic address:

A portable electrochemical sensor was developed to determine xylazine in spiked beverages by adsorptive stripping voltammetry (AdSV). The sensor was based on a graphene nanoplatelets-modified screen-printed carbon electrode (GNPs/SPCE). The electrochemical behavior of xylazine at the GNPs/SPCE was an adsorption-controlled irreversible oxidation reaction. The loading of graphene nanoplatelets (GNPs) on the modified SPCE, electrolyte pH, and AdSV accumulation potential and time were optimized. Under optimal conditions, the GNPs/SPCE provided high sensitivity, linear ranges of 0.4-6.0 mg L (r = 0.997) and 6.0-80.0 mg L (r = 0.998) with a detection limit of 0.1 mg L and a quantitation limit of 0.4 mg L. Repeatability was good. The accuracy of the proposed sensor was investigated by spiking six beverage samples at 1.0, 5.0, and 10.0 mg L. The recoveries from this method ranged from 80.8 ± 0.2-108.1 ± 0.3 %, indicating the good accuracy of the developed sensor. This portable electrochemical sensor can be used to screen for xylazine in beverage samples as evidence in cases of sexual assault or robbery.
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http://dx.doi.org/10.1016/j.jpba.2021.113958DOI Listing
May 2021

Subnanomolar detection of promethazine abuse using a gold nanoparticle-graphene nanoplatelet-modified electrode.

Mikrochim Acta 2020 Nov 9;187(12):646. Epub 2020 Nov 9.

Center of Excellence for Trace Analysis and Biosensor, Prince of Songkla University, Hat Yai, Songkhla, 90112, Thailand.

A simple, sensitive, and effective adsorptive stripping voltammetric sensor for the detection of trace-level promethazine was created based on a gold nanoparticle-graphene nanoplatelet-modified glassy carbon electrode (AuNP-GrNP/GCE). AuNP-GrNP nanocomposites were synthesized using an electroless deposition process, and the morphology was characterized using UV-vis spectroscopy, Fourier transform infrared spectroscopy, field emission scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The electrochemical behavior and detection of promethazine at the AuNP-GrNP/GCE were investigated utilizing cyclic voltammetry and adsorptive stripping voltammetry. The AuNP-GrNP/GCE showed outstanding synergistic electrochemical activity for promethazine oxidation, a highly active surface area, great adsorptivity, and outstanding catalytic properties. The electrolyte pH, amount of AuNP-GrNP nanocomposite, preconcentration potential (vs. Ag/AgCl), and time were optimized to obtain a high performance electrochemical sensor. Under optimal conditions, the proposed sensor displayed two linear concentration ranges from 1.0 nmol L to 1.0 μmol L and from 1.0 to 10 μmol L. The limits of detection and quantitation were 0.40 and 1.4 nmol L, respectively. This sensor displayed high sensitivity, a capability for rapid analysis, and excellent repeatability and reproducibility. The developed sensor was effective and practical for promethazine detection in biological fluids and forensic samples, and the obtained results exhibited excellent agreement with the results obtained using the method described in the British Pharmacopoeia. Graphical abstract.
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http://dx.doi.org/10.1007/s00604-020-04616-wDOI Listing
November 2020

Electrochemical sensor for the quantification of iodide in urine of pregnant women.

Mikrochim Acta 2020 Oct 6;187(11):591. Epub 2020 Oct 6.

Center of Excellence for Trace Analysis and Biosensor, Prince of Songkla University, Hat Yai, Songkhla, 90112, Thailand.

An electrochemical method has been developed to determine iodide in urine using an electrode modified with silver oxide microparticles-poly acrylic acid/poly vinyl alcohol (AgOMPs-PAA/PVA). Silver oxide particles were formed by electrochemical oxidation via cyclic voltammetry. The modified electrode exhibited an excellent response to iodide detection by cathodic stripping voltammetry. The fabrication and operation conditions were optimized in terms of PVA concentration, KHPO concentration, amount of AgMPs-PAA/PVA, number of cycles for oxide formation, electrolyte, applied potential (vs. Ag/AgCl), and time. Under the optimum conditions, iodide determination produced a linear range from 1 to 40 μM. The limit of detection was 0.3 μM. Precision was found to be within 7.4% RSD. The developed method was applied to the determination of iodide in urine samples of pregnant women with satisfying recoveries (86 ± 1 to 108 ± 1%). Graphical abstract.
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http://dx.doi.org/10.1007/s00604-020-04488-0DOI Listing
October 2020

Studying the preparation, electrochemical performance testing, comparison and application of a cost-effective flexible graphene working electrode.

J Colloid Interface Sci 2021 Feb 15;583:487-498. Epub 2020 Sep 15.

Center of Excellence for Trace Analysis and Biosensor, Prince of Songkla University, Hat Yai, Songkhla 90112, Thailand; Center of Excellence for Innovation in Chemistry, Faculty of Science, Prince of Songkla University, Hat Yai, Songkhla 90112, Thailand; Division of Health and Applied Sciences, Faculty of Science, Prince of Songkla University, Hat Yai, Songkhla 90112, Thailand. Electronic address:

-A cost-effective flexible graphene working electrode (FGWE) was fabricated using overhead projector transparent film (OPTF) and a screen-printing technique. The surface morphology and electrochemical behavior of the electrode were characterized by scanning electron microscopy and cyclic voltammetry. The electrode presented a very thin layer of conductive ink (16.0 ± 0.7 µm) on a large effective surface area (0.301 ± 0.001 cm). The anodic peak current density (j) of acetaminophen (ACT) in FGWE was 5.2, 3.7, 3.5 and 6.0 times greater than the j of glassy carbon electrode (GCE), flexible carbon working electrode (FCWE), SPE1, and SPE2, respectively. The electrochemical performance of FGWE toward ACT was evaluated by differential pulse voltammetry. Under optimized condition, ACT was quantified in a range of  4-100 µM, with good sensitivity, good accuracy (recovery = 82.3 ± 0.4 to 106 ± 3%), and excellent precision. FGWE was applied to determine ACT in commercial pharmaceutical formulations. The results of the study are in good agreement with those obtained by the standard spectrophotometric method. These results indicate that disposable FGWE is particularly useful for the detection of ACT, and its performance may serve as a platform for cost-effective flexible electrochemical sensors.
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http://dx.doi.org/10.1016/j.jcis.2020.08.121DOI Listing
February 2021

Multiplexed label-free electrochemical immunosensor for breast cancer precision medicine.

Anal Chim Acta 2020 Sep 25;1130:60-71. Epub 2020 Jul 25.

Center of Excellence for Trace Analysis and Biosensor, Prince of Songkla University, Hat Yai, Songkhla, 90112, Thailand; Center of Excellence for Innovation in Chemistry, Faculty of Science, Prince of Songkla University, Hat Yai, Songkhla 90112, Thailand; Department of Applied Science, Faculty of Science, Prince of Songkla University, Hat Yai, Songkhla, 90112, Thailand. Electronic address:

A novel multiplexed label-free electrochemical immunosensor was fabricated using graphene/methylene blue-chitosan/antibody and bovine serum albumin on indium tin oxide glass electrode for the simultaneous determination of three types of tumor markers including carcinoembryonic antigen (CEA), cancer antigens 153 (CA153), and cancer antigen 125 (CA125). Cyclic voltammetry, electrochemical impedance spectroscopy, and scanning electron microscopy were employed to monitor each fabrication step. Under the optimized experiment conditions, the immunosensor exhibited good reproducibility and selectivity with linear ranges of 0.10-1.00 pg mL and 1.00-100.00 pg mL for CEA, 0.10-2.50 mU mL and 2.50-100.00 mU mL for CA153, 0.10-2.50 mU mL and 2.50-100.00 mU mL for CA125, a detection limit of 0.04 pg mL for CEA, 0.04 mU mL for CA153, and 0.04 mU mL for CA125. This electrochemical immunosensor was successfully applied to detect three tumor markers in blood serum samples with good recoveries. The reliability of the electrochemical immunosensor to detect three tumor markers in blood serum samples was in good agreement (P > 0.05) with that of the enzyme-linked fluorescent assay method.
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http://dx.doi.org/10.1016/j.aca.2020.07.021DOI Listing
September 2020

Porous palladium-poly(3,4-ethylenedioxythiophene)-coated carbon microspheres/graphene nanoplatelet-modified electrode for flow-based-amperometric hydrazine sensor.

Mikrochim Acta 2020 09 2;187(9):539. Epub 2020 Sep 2.

Center of Excellence for Trace Analysis and Biosensor, Prince of Songkla University, Hat Yai, Songkhla, 90112, Thailand.

A highly stable flow-injection amperometric hydrazine sensor was developed based on a glassy carbon electrode modified with palladium-poly(3,4-ethylene dioxythiophene) coated on carbon microspheres/graphene nanoplatelets (Pd-PEDOT@CM/GNP/GCE). The Pd-PEDOT@CM/GNP composite was characterized by scanning electron microscopy and energy-dispersive x-ray analysis (SEM/EDX). The modified GCE was electrochemically characterized using cyclic voltammetry and chronoamperometry. The electrocatalytic activity of the Pd-PEDOT@CM/GNP/GCE toward hydrazine oxidation was significantly better than the activity of a bare GCE, a CM/GCE, a GNP/GCE, a Pd-PEDOT/GCE, and a Pd-PEDOT@CM/GCE. The sensor operated best at a low working potential of + 0.10 V (vs. Ag/AgCl). Under optimal conditions, sensitivity toward hydrazine detection and operational stability (601 injections/one electrode preparation) were excellent. The response was linear from 1.0 to 100 μmol L and from 100 to 5000 μmol L with a detection limit of 0.28 ± 0.02 μmol L and high sensitivity of 0.200 μA μM cm. The sensor showed good repeatability (relative standard deviation (RSD) < 1.4%, n = 15), reproducibility (RSD < 2.7%, n = 6), and anti-interference characteristics toward hydrazine detection. The feasibility of the electrochemical sensor was proved by the successful determination of hydrazine in water samples, and the results were in good agreement with those obtained from spectrophotometric analysis. Graphical abstract.
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http://dx.doi.org/10.1007/s00604-020-04470-wDOI Listing
September 2020

Bio-PEDOT: Modulating Carboxyl Moieties in Poly(3,4-ethylenedioxythiophene) for Enzyme-Coupled Bioelectronic Interfaces.

ACS Appl Mater Interfaces 2020 Sep 20;12(35):39841-39849. Epub 2020 Aug 20.

Biosensors and Bioelectronics Centre, Department of Physics, Chemistry and Biology, Linköping University, SE-581 83 Linköping, Sweden.

Modulation of chemical functional groups on conducting polymers (CPs) provides an effective way to tailor the physicochemical properties and electrochemical performance of CPs, as well as serves as a functional interface for stable integration of CPs with biomolecules for organic bioelectronics (OBEs). Herein, we introduced a facile approach to modulate the carboxylate functional groups on the PEDOT interface through a systematic evaluation on the effect of a series of carboxylate-containing molecules as counterion dopant integrated into the PEDOT backbone, including acetate as monocarboxylate (mono-COO), malate as dicarboxylate (di-COO), citrate as tricarboxylate (tri-COO), and poly(acrylamide--acrylate) as polycarboxylate (poly-COO) bearing different amounts of molecular carboxylate moieties to create tunable PEDOT:COO interfaces with improved polymerization efficiency. We demonstrated the modulation of PEDOT:COO interfaces with various granulated morphologies from 0.33 to 0.11 μm, tunable surface carboxylate densities from 0.56 to 3.6 μM cm, and with improved electrochemical kinetics and cycling stability. We further demonstrated the effective and stable coupling of an enzyme model lactate dehydrogenase (LDH) with the optimized PEDOT:poly-COO interface via simple covalent chemistry to develop biofunctionalized PEDOT (Bio-PEDOT) as a lactate biosensor. The biosensing mechanism is driven by a sequential bioelectrochemical signal transduction between the bio-organic LDH and organic PEDOT toward the concept of all-polymer-based OBEs with a high sensitivity of 8.38 μA mM cm and good reproducibility. Moreover, we utilized the LDH-PEDOT biosensor for the detection of lactate in spiked serum samples with a high recovery value of 91-96% and relatively small RSD in the range of 2.1-3.1%. Our findings provide a new insight into the design and optimization of functional CPs, leading to the development of new OBEs for sensing, biosensing, bioengineering, and biofuel cell applications.
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http://dx.doi.org/10.1021/acsami.0c10270DOI Listing
September 2020

Adsorption and determination of sibutramine in illegal slimming product using porous graphene ink-modified electrode.

Talanta 2020 May 27;212:120788. Epub 2020 Jan 27.

Department of Applied Science, Faculty of Science, Prince of Songkla University, Hat Yai, Songkhla, 90112, Thailand; Center of Excellence for Trace Analysis and Biosensor, Prince of Songkla University, Hat Yai, Songkhla, 90112, Thailand; Center of Excellence for Innovation in Chemistry, Faculty of Science, Prince of Songkla University, HatYai, Songkhla, 90112, Thailand. Electronic address:

This work presents a new material, i.e., a porous graphene ink to modify on the GCE surface (PGr-ink/GCE) to improve sensitivity by increasing the surface area of the electrode for the electrochemical determination of sibutramine. The surface characterization and electrochemical adsorption behavior of the PGr-ink/GCE toward sibutramine were investigated using scanning electron microscopy (SEM), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), ATR-FTIR spectroscopy and square wave adsorptive stripping voltammetry (SWAdSV). The PGr-ink/GCE exhibited a distinctive anodic response towards sibutramine using SWAdSV in BR buffer (pH 8.00) with a sensitivity 4 times higher than the bare GCE. Under the optimum conditions, the modified electrode showed good electrochemical adsorption and detection of sibutramine by the SWAdSV method with two ranges of linear concentration from 0.015 to 10.0 μg mL and 10-50 μg mL. The limit of detection and quantitation were 5 ng mL and 15 ng mL, respectively. Over a short analysis time (180 s), the sensor exhibited high sensitivity (10.9 μAμgmLcm), good reproducibility (RSD <3.4% n = 6), repeatability (RSD between 1.8 and 9.8% (n = 15)), excellent anti-interference properties and was successfully applied for the quantification of sibutramine in different brands of illegal slimming products with good recoveries (93 ± 4-104 ± 1%). The developed electrochemical sibutramine sensor is suitable for application in detecting illegal components in slimming products.
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http://dx.doi.org/10.1016/j.talanta.2020.120788DOI Listing
May 2020

Phage-based capacitive biosensor for Salmonella detection.

Talanta 2018 Oct 15;188:658-664. Epub 2018 Jun 15.

Trace Analysis and Biosensor Research Center, Prince of Songkla University, Hat Yai, Songkhla 90112, Thailand; Center of Excellence for Innovation in Chemistry, Faculty of Science, Prince of Songkla University, Hat Yai, Songkhla 90112, Thailand; Department of Physics, Faculty of Science, Prince of Songkla University, Hat Yai, Songkhla 90112, Thailand. Electronic address:

This article reports the detection of Salmonella spp. based on M13 bacteriophage in a capacitive flow injection system. Salmonella-specific M13 bacteriophage was immobilized on a polytyramine/gold surface using glutaraldehyde as a crosslinker. The M13 bacteriophage modified electrode can specifically bind to Salmonella spp. via the amino acid groups on the filamentous phage. An alkaline solution was used to break the binding between the sensing surface and the analyte to allow renewable use up to 40 times. This capacitive system provided good reproducibility with a relative standard deviation (RSD) of 1.1%. A 75 µL min flow rate and a 300 µL sample volume provided a wide linear range, from 2.0 × 10 to 1.0 × 10 cfu mL, with a detection limit of 200 cfu mL. Bacteria concentration can be analyzed within 40 min after the sample injection. When applied to test real samples (raw chicken meat) it provided good recoveries (100-111%). An enrichment process was also explored to increase the bacteria concentration, enabling a quantitative detection of Salmonella spp. This biosensor opens a new opportunity for the detection of pathogenic bacteria using bacteriophage.
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http://dx.doi.org/10.1016/j.talanta.2018.06.033DOI Listing
October 2018

Pyrrolidinyl PNA polypyrrole/silver nanofoam electrode as a novel label-free electrochemical miRNA-21 biosensor.

Biosens Bioelectron 2018 Apr 6;102:217-225. Epub 2017 Nov 6.

Trace Analysis and Biosensor Research Center, Prince of Songkla University, Hat Yai, Songkhla 90112, Thailand; Center of Excellence for Innovation in Chemistry, Faculty of Science, Prince of Songkla University, Hat Yai, Songkhla 90112, Thailand; Department of Physics, Faculty of Science, Prince of Songkla University, Hat Yai, Songkhla 90112, Thailand. Electronic address:

A label-free electrochemical miRNA biosensor was developed based on a pyrrolidinyl peptide nucleic acid (acpcPNA)/polypyrrole (PPy)/silver nanofoam (AgNF) modified electrode. The AgNF was electrodeposited as redox indicator on a gold electrode, which was then functionalized with an electropolymerized layer of PPy, a conducting polymer, to immobilize the PNA probes. The fabrication process was investigated by electrochemical impedance spectroscopy. The biosensor was used to detect miRNA-21, a biomarker abnormally expressed in most cancers. The signal was monitored by the change in current of the AgNF redox reaction before and after hybridization using cyclic voltammetry. Two PNA probe lengths were investigated and the longer probe exhibited a better performance. Nucleotide overhangs on the electrode side affected the signal more than overhangs on the solution side due to the greater insulation of the sensing surface. Under optimal conditions, the electrochemical signal was proportional to miRNA-21 concentrations between 0.20fM and 1.0nM, with a very low detection limit of 0.20fM. The biosensor showed a high specificity which could discriminate between complementary, single-, doubled-base mismatched, and non-complementary targets. Three out of the seven tested plasma samples provided detectable concentrations (63 ± 4, 111 ± 4 and 164 ± 7fM). The sensor also showed good recoveries (81-119%). The results indicated the possibilities of this biosensor for analysis without RNA extraction and/or amplification, making the sensor potentially useful for both the prognosis and diagnosis of cancer in clinical application.
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http://dx.doi.org/10.1016/j.bios.2017.11.024DOI Listing
April 2018

Capacitive antibacterial susceptibility screening test with a simple renewable sensing surface.

Biosens Bioelectron 2017 Oct 27;96:84-88. Epub 2017 Apr 27.

Trace Analysis and Biosensor Research Center, Prince of Songkla University, Hat Yai, Songkhla 90112, Thailand; Center of Excellence for Innovation in Chemistry, Faculty of Science, Prince of Songkla University, Hat Yai, Songkhla 90112, Thailand; Department of Physics, Faculty of Science, Prince of Songkla University, Hat Yai, Songkhla 90112, Thailand. Electronic address:

A simple renewable surface for a rapid antibacterial susceptibility test has been demonstrated. The 3-aminophenylboronic acid (3-APBA) modified electrode bind with cis-diol groups on the cell wall of both gram positive and gram negative bacteria. The detection of antibacterial susceptibility response by a capacitive system can be done within a short time, 2.5h for the whole process, with good repeatability of the electrode's preparation. An acid solution, could break the bonding between 3-APBA and the bacteria, which were then easily removed by the fluid flow, renewing the sensing surface for the next test. This modified electrode can be reused up to 35 times. This sensor is useful for testing the susceptibility of bacteria to antibacterial agents that affect their cell wall. Results from the capacitive sensor corresponded well with the antimicrobial information in the literature and to the morphology of the treated bacteria revealed by scanning electron microscopy. Antimicrobial susceptibility to natural products could also be easily tested.
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http://dx.doi.org/10.1016/j.bios.2017.04.042DOI Listing
October 2017

4-mercaptophenylboronic acid functionalized gold nanoparticles for colorimetric sialic acid detection.

Biosens Bioelectron 2016 Nov 26;85:743-750. Epub 2016 May 26.

Trace Analysis and Biosensor Research Center, Prince of Songkla University, Hat Yai, Songkhla 90112, Thailand; Center of Excellence for Innovation in Chemistry, Faculty of Science, Prince of Songkla University, Hat Yai, Songkhla 90112, Thailand; Department of Physics, Faculty of Science, Prince of Songkla University, Hat Yai, Songkhla 90112, Thailand. Electronic address:

A simple and selective colorimetric sensor for sialic acid detection, based on the aggregation of 4-mercaptophenylboronic acid functionalized gold nanoparticles (4-MPBA-AuNPs) was developed. The color of the solution changed from wine-red to blue after binding with sialic acid. The colorimetric sensor provided good analytical performances with a linear dynamic range of 80µM to 2.00mM and a 68±2µM limit of detection without any effect from possible interferences and sample matrix. In addition, the quantitative results were obtained within only 10min. This developed sensor was used to detect sialic acid in blood serum samples and the results were in good agreement with those from the current periodate-resorcinol method (P>0.05) thus indicating that this developed colorimetric sensor can be used as an alternative method for sialic acid detection with a shorter analysis time and a high accuracy.
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http://dx.doi.org/10.1016/j.bios.2016.05.083DOI Listing
November 2016

Enhancing capacitive DNA biosensor performance by target overhang with application on screening test of HLA-B*58:01 and HLA-B*57:01 genes.

Biosens Bioelectron 2016 Aug 28;82:99-104. Epub 2016 Mar 28.

Trace Analysis and Biosensor Research Center, Prince of Songkla University, Hat Yai, Songkhla 90112, Thailand; Center of Excellence for Innovation in Chemistry, Faculty of Science, Prince of Songkla University, Hat Yai, Songkhla 90112, Thailand; Department of Physics, Faculty of Science, Prince of Songkla University, Hat Yai, Songkhla 90112, Thailand. Electronic address:

A highly sensitive label-free DNA biosensor based on PNA probes immobilized on a gold electrode was used to detect a hybridization event. The effect of a target DNA overhang on the hybridization efficiency was shown to enhance the detected signal and allowed detection at a very low concentration. The sensors performances were investigated with a complementary target that had the same length as the probe, and the signal was compared to the target DNAs with different lengths and overhangs. A longer target DNA overhang was found to provide a better response. When the overhang was on the electrode side the signal enhancement was greater than when the overhang was on the solution side due to the increased thickness of the sensing surface, hence produced a larger capacitance change. Using conformationally constrained acpcPNA probes, double stranded DNA was detected sensitively and specifically without any denaturing step. When two acpcPNA probes were applied for the screening test for the double stranded HLA-B*58:01 and HLA-B*57:01 genes that are highly similar, the method differentiated the two genes in all samples. Both purified and unpurified PCR products gave comparable results. This method would be potentially useful as a rapid screening test without the need for purification and denaturation of the PCR products.
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http://dx.doi.org/10.1016/j.bios.2016.03.065DOI Listing
August 2016

Highly-sensitive label-free electrochemical carcinoembryonic antigen immunosensor based on a novel Au nanoparticles-graphene-chitosan nanocomposite cryogel electrode.

Anal Chim Acta 2015 Jan 13;853:521-532. Epub 2014 Oct 13.

Trace Analysis and Biosensor Research Center, Prince of Songkla University, Hat Yai, Songkhla 90112, Thailand; Center of Excellence for Innovation in Chemistry, Faculty of Science, Prince of Songkla University, Hat Yai, Songkhla 90112, Thailand; Department of Physics, Faculty of Science, Prince of Songkla University, Hat Yai, Songkhla 90112, Thailand. Electronic address:

For the first time, a simple and highly sensitive label-free electrochemical carcinoembryonic antigen (CEA) immunosensor based on a cryogel electrode has been developed and tested. The as-prepared nanocomposite combined the advantages of the graphene, AuNPs and chitosan (AuNPs-GP-CS) together with the ease of preparing a cryogel coupled to a silver deposition, to act as a redox mediator, on a Au electrode. Under the optimal conditions, the decrease of the cyclic voltammetry (CV) silver peak current was proportional to the CEA concentration over a range of from 1.0×10(-6) to 1.0 ng mL(-1) with a detection limit of 2.0×10(-7) ng mL(-1). This AuNPs-GP-CS cryogel electrode gave a 1.7 times higher sensitivity and 25 times lower detection limit than the non-cryogel electrode. Moreover, the proposed electrochemical immunosensor exhibited good selectivity, reproducibility and stability. When applied to analyse clinical serum samples, the data determined by the developed immunosensor were in agreement with those obtained by the current hospital analysis system (enzyme linked fluorescent assay) (P>0.05), to indicate that the immunosensor would be potentially useful for clinical diagnostics.
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http://dx.doi.org/10.1016/j.aca.2014.10.006DOI Listing
January 2015

A novel molecularly imprinted chitosan-acrylamide, graphene, ferrocene composite cryogel biosensor used to detect microalbumin.

Analyst 2014 Dec 13;139(23):6160-7. Epub 2014 Oct 13.

Trace Analysis and Biosensor Research Center, Prince of Songkla University, Hat Yai, Songkhla 90112, Thailand.

A novel highly sensitive and selective molecularly imprinted polymer (MIP) cryogel biosensor for determination of microalbumin in urine samples was fabricated. The MIP gel was prepared based on the graft copolymerization of acrylamide with N,N'-methylenebisacrylamide on chitosan using human serum albumin (HSA) as the template. The sub-zero polymerization allowed the solvent to form ice crystals and left a macroporous cryogel structure when it was thawed. After removing the template, the specific imprinted surface on cryogel pore walls was used to detect HSA via a redox mediator (ferrocene), entrapped in the cryogel, using differential pulse voltammetry (DPV). The electrochemical detection was improved by the presence of graphene that has been composited within the polymer. For determination of albumin, the fabricated MIP cryogel biosensor showed a high sensitivity with a wide linear range of 1.0 × 10(-4) to 1.0 × 10(1) mg L(-1) and a low limit of detection of 5.0 × 10(-5) mg L(-1) (S/N = 3). The sensor also provided a very good reusability, i.e., the sensitivity remained >90% after 9 cycles of binding-rewashing (18 analyses per cycle), while the sensitivity only decreased to 90% after 6 weeks of storage at room temperature. The biosensor also showed a good selectivity, both against bovine serum albumin (BSA) and some common possible interfering compounds normally present in urine (ascorbic acid, uric acid, urea, sodium, chloride, potassium and creatinine). The excellent performance of the biosensor was confirmed by analyzing microalbumin in urine samples, and results were in good agreement with those obtained by the standard immunoturbidimetric method (P > 0.05).
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http://dx.doi.org/10.1039/c4an01000kDOI Listing
December 2014

Electrochemical detection of the disease marker human chitinase-3-like protein 1 by matching antibody-modified gold electrodes as label-free immunosensors.

Bioelectrochemistry 2015 Feb 30;101:106-13. Epub 2014 Jul 30.

Biochemistry-Electrochemistry Research Unit, Schools of Chemistry and Biochemistry, Suranaree University of Technology, Nakhon Ratchasima 30000, Thailand. Electronic address:

Tissue inflammation, certain cardiovascular syndromes and the occurrence of some solid tumors are correlated with raised serum concentrations of human chitinase-3-like protein 1 (YKL-40), a mammalian chitinase-like glycoprotein, which has become the subject of current research. Here we report the construction and characterization of an electrochemical platform for label-free immunosensing of YKL-40. Details of the synthesis of YKL-40 and production of anti-YKL-40 immunoglobulin G (IgG) are provided and cross-reactivity tests presented. Polyclonal anti-YKL-40 IgG was immobilized on gold electrodes and the resulting immunosensors were operated in an electrochemical flow system with capacitive signal generation. The strategy offered a wide linear detection range (0.1μg/L to 1mg/L) with correlation coefficients (R(2)) above 0.99 and good sensitivity (12.28±0.27nF/cm(2) per decade of concentration change). Additionally, the detection limit of 0.07±0.01μg/L was well below that of optical enzyme-linked immunosorbent assays (ELISAs), which makes the proposed methodology a promising alternative for YKL-40 related disease studies.
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http://dx.doi.org/10.1016/j.bioelechem.2014.07.006DOI Listing
February 2015

Label-free capacitive DNA sensor using immobilized pyrrolidinyl PNA probe: effect of the length and terminating head group of the blocking thiols.

Biosens Bioelectron 2012 Oct-Dec;38(1):430-5. Epub 2012 Jun 19.

Trace Analysis and Biosensor Research Center, Prince of Songkla University, Hat Yai, Songkhla 90112, Thailand.

This paper reports, for the first time, the influence of the length and the terminating head group of blocking thiols on the sensitivity and specificity of a label-free capacitive DNA detection system using immobilized pyrrolidinyl peptide nucleic acid (acpcPNA) probes. A C-terminal lysine-modified acpcPNA was immobilized through four different alkanethiol self-assembled monolayers (SAMs), i.e., 3-mercaptopropionic acid (MPA), thioctic acid (TA), thiourea (TU) and mercaptosuccinic acid (MSA). The hybridization between the acpcPNA probes and the target DNA was directly measured using the capacitive system. Five blocking thiols of various lengths (C=3, 6, 8, 9 and 11), with the -OH terminating head group, i.e., 3-mercapto-1-propanol (3-MPL), 6-mercapto-1-hexanol (6-MHL), 8-mercapto-1-octanol (8-MOL), 9-mercapto-1-nonanol (9-MNL), 11-mercapto-1-undecanol (11-MUL) and another blocking thiol (C=11) with a -CH(3) terminating head group, and 1-dodecanethiol (1-DDT) were investigated. The blocking thiol with the same length as the total spacer of the immobilized acpcPNA gave the highest sensitivity and specificity with the -OH terminating head group providing a slightly better signal than the -CH(3) group. Under the optimized conditions, the immobilized acpcPNA probes provided a wide linear range for DNA detection (1.0 × 10(-11)-1.0 × 10(-8)M) with a very low detection limit in the picomolar range. The modified acpcPNA electrode could be reused through at least 58 cycles. The high sensitivity and very low detection limits are potentially useful for the analysis of ultra-trace levels of DNA in samples. Preliminary studies were also performed to see the effect of probe concentration and target length.
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http://dx.doi.org/10.1016/j.bios.2012.06.021DOI Listing
December 2012

Label-free capacitive immunosensors for ultra-trace detection based on the increase of immobilized antibodies on silver nanoparticles.

Anal Chim Acta 2011 Aug 1;699(2):232-41. Epub 2011 Jun 1.

Trace Analysis and Biosensor Research Center, Prince of Songkla University, Hat Yai, Thailand.

Detection of ultra-trace amounts of antigens by label-free capacitive immunosensors was investigated using electrodes modified with silver nanoparticles (AgNPs) that allows for an increase in the amount of immobilized antibodies. The optimal amount of AgNPs that provided the highest immobilization yield was 48 pmol (in 2.0 mL). The performances of immunosensor electrodes for human serum albumin prepared with AgNPs, were compared to electrodes prepared with gold nanoparticles. The two systems provided the same linear range (1.0×10(-18) to 1.0×10(-10) M) and detection limit (1.0×10(-18) M). The system with AgNPs was used to analyze albumin in urine samples and the results agreed well with the immunoturbidimetric assay (P>0.05). Electrodes modified with AgNPs and appropriate antibodies were tested for their performances to detect analytes of different sizes. For a macromolecule (human serum albumin) the incorporation of AgNPs improved the detection limit from 100 to 1 aM. For small molecules, microcystin-LR and penicillin G, the detection limits were lowered from 100 and 10 fM to 10 and 0.7 fM, respectively. The high sensitivity and very low detection limits are potentially useful for the analysis of toxins or residues present in samples at ultra-trace levels and this method could easily be applied to other affinity pairs.
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http://dx.doi.org/10.1016/j.aca.2011.05.038DOI Listing
August 2011

Ultra trace analysis of small molecule by label-free impedimetric immunosensor using multilayer modified electrode.

Biosens Bioelectron 2011 Jul 23;26(11):4571-8. Epub 2011 May 23.

Trace Analysis and Biosensor Research Center, Prince of Songkla University, Hat Yai, Songkhla 90112, Thailand.

A multilayer electrode modified with a self-assembled thiourea monolayer (SATUM) followed by gold nanoparticles (AuNPs), mercaptosuccinic acid (MSA) and antibody was investigated for the detection of ultra trace amount of a small molecule (chloramphenicol) in an impedimetric system. The formation of the antibody-antigen complex at the electrode surface caused the impedance to increase. Under optimum conditions three modified electrodes were compared the SATUM/AuNPs/MSA electrode provided a wide linear range (0.50-10) × 10⁻¹⁶ M, and a very low determination limit of 1.0 × 10⁻¹⁶ M. This determination limit was much lower than the SATUM/AuNPs electrode, 1.0 × 10⁻¹⁵ M, and SATUM electrode, 4.7 × 10⁻¹⁴ M. The modified electrode provided good selectivity for chloramphenicol detection and can be reused up to 45 times with a relative standard deviation of lower than 4%. When applied to determine chloramphenicol in shrimp samples, the results agreed well with those obtained by the high-performance liquid chromatography coupled with a photo diode array detector (P > 0.05). The developed system can be applied to detect other small molecules using appropriate affinity binding pairs.
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http://dx.doi.org/10.1016/j.bios.2011.05.029DOI Listing
July 2011

Development and application of a real-time capacitive sensor.

Biosens Bioelectron 2011 Jan 28;26(5):2466-72. Epub 2010 Oct 28.

Trace Analysis and Biosensor Research Center, Prince of Songkla University, Hat Yai, Songkhla 90112, Thailand.

A real-time capacitive sensor based on a potentiostatic step method was developed. It can display in real-time the evoked current waveform, capacitance and the electrical resistance of elements serially connected to the insulation layer on the electrode as a function of time as well as the ohmic resistance of the insulation layer. These features enable the user to observe the association and dissociation of the affinity binding pairs and to evaluate the insulating property of the electrode surface during measurement. The system allows the setting of potential pulse height, pulse interval, gain, filter, and sampling frequency, enabling the system to be more flexible. The performance of the system was firstly evaluated with equivalent circuits. Under suitable parameter settings it provided good accuracy of both the capacitance and resistance. Using the affinity binding pair of human serum albumin (HSA) and anti human serum albumin (anti-HSA) the measured capacitance change was used for the direct detection of HSA. The developed system provided the same sensitivity as the commercially available potentiostat (P>0.05). The proposed system was then applied to analyse HSA in real urine samples and the results agreed well with the immunoturbidimetric assay (P>0.05). The proposed system can be applied for capacitance measurement to directly detect other target analytes using different affinity binding pairs. Other applications such as kinetics analysis of the interaction between affinity bindings, thickness analysis, and the study of the insulation property of the modified layer are also promising.
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http://dx.doi.org/10.1016/j.bios.2010.10.033DOI Listing
January 2011

Affinity sensor using 3-aminophenylboronic acid for bacteria detection.

Biosens Bioelectron 2010 Oct 7;26(2):357-64. Epub 2010 Aug 7.

Trace Analysis and Biosensor Research Center, Center for Innovation in Chemistry, Department of Chemistry, Faculty of Science, Prince of Songkla University, Hat Yai, Songkhla 90112, Thailand.

Boronic acid that can reversibly bind to diols was used to detect bacteria through its affinity binding reaction with diol-groups on bacterial cell walls. 3-aminophenylboronic acid (3-APBA) was immobilized on a gold electrode via a self-assembled monolayer. The change in capacitance of the sensing surface caused by the binding between 3-APBA and bacteria in a flow system was detected by a potentiostatic step method. Under optimal conditions the linear range of 1.5×10(2)-1.5×10(6) CFU ml(-1) and the detection limit of 1.0×10(2) CFU ml(-1) was obtained. The sensing surface can be regenerated and reused up to 58 times. The method was used for the analysis of bacteria in several types of water, i.e., bottled, well, tap, reservoir and wastewater. Compared with the standard plate count method, the results were within one standard deviation of each other. The proposed method can save both time and cost of analysis. The electrode modified with 3-APBA would also be applicable to the detection of other cis-diol-containing analytes. The concept could be extended to other chemoselective ligands, offering less expensive and more robust affinity sensors for a wide range of compounds.
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http://dx.doi.org/10.1016/j.bios.2010.08.005DOI Listing
October 2010

Capacitive biosensor for detection of endotoxin.

Anal Bioanal Chem 2007 Sep 27;389(2):517-25. Epub 2007 Jul 27.

Department of Biotechnology, Center for Chemistry and Chemical Engineering, Lund University, Box 124, 221 00, Lund, Sweden.

A capacitive biosensor for the detection of bacterial endotoxin has been developed. Endotoxin-neutralizing protein derived from American horseshoe crab was immobilized to a self-assembled thiol layer on a biosensor transducer (Au). Upon injection of a sample containing endotoxin, a decrease in the observed capacitive signal was registered. Endotoxin could be determined under optimum conditions with a detection limit of 1.0 x 10(-13) M and linearity ranging from 1.0 x 10(-13) to 1.0 x 10(-10) M. Good agreement was achieved when applying endotoxin preparations purified from an Escherichia coli cultivation to the capacitive biosensor system, utilizing the conventional method for quantitative endotoxin determination, the Limulus amebocyte lysate test as a reference. The capacitive biosensor method was statistically tested with the Wilcoxon signed rank test, which proved the system is acceptable for the quantitative analysis of bacterial endotoxin (P<0.05).
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http://dx.doi.org/10.1007/s00216-007-1443-4DOI Listing
September 2007

Microfluidic conductimetric bioreactor.

Biosens Bioelectron 2007 Jun 16;22(12):3064-71. Epub 2007 Jan 16.

Biophysics Research Unit of Biosensors and Biocurrents, Prince of Songkla University, Hat Yai, Songkhla 90112, Thailand.

A microfluidic conductimetric bioreactor has been developed. Enzyme was immobilized in the microfluidic channel on poly-dimethylsiloxane (PDMS) surface via covalent binding method. The detection unit consisted of two gold electrodes and a laboratory-built conductimetric transducer to monitor the increase in the conductivity of the solution due to the change of the charges generated by the enzyme-substrate catalytic reaction. Urea-urease was used as a representative analyte-enzyme system. Under optimum conditions urea could be determined with a detection limit of 0.09 mM and linearity in the range of 0.1-10 mM (r=0.9944). The immobilized urease on the microchannel chip provided good stability (>30 days of operation time) and good repeatability with an R.S.D. lower than 2.3%. Good agreement was obtained when urea concentrations of human serum samples determined by the microfluidic flow injection conductimetric bioreactor system were compared to those obtained using the Berthelot reaction (P<0.05). After prolong use the immobilized enzyme could be removed from the PDMS microchannel chip enabling new active enzyme to be immobilized and the chip to be reused.
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http://dx.doi.org/10.1016/j.bios.2007.01.001DOI Listing
June 2007

A comparative study of capacitive immunosensors based on self-assembled monolayers formed from thiourea, thioctic acid, and 3-mercaptopropionic acid.

Biosens Bioelectron 2006 Aug 7;22(2):233-40. Epub 2006 Feb 7.

Biophysics Research Unit, Biosensors and Biocurrents, Prince of Songkla University, Hat Yai, Songkhla 90112, Thailand.

A procedure was developed for the covalent coupling of anti-alpha-fetoprotein antibody (anti-AFP) to a gold surface modified with a self-assembled monolayer (SAM) of thiourea (TU). The performance of the SAM-antibody layer was compared to those of similar layers based on thioctic acid (TA) and 3-mercaptopropionic acid (MPA) by using flow injection capacitive immunosensor system. Covalent coupling of anti-AFP on self-assembled thiourea monolayer (SATUM) modified gold electrode can be used to detect alpha-fetoprotein with high efficiency, similar sensitivity, the same linear range (0.01-10 microgl(-1)) and detection limit (10 ngl(-1)) as those obtained from sensors based on self-assembled thioctic acid monolayer (SATAM) and self-assembled 3-mercaptopropionic acid monolayer (SAMPAM). The system is specific for alpha-fetoprotein and can be regenerated and reused up to 48 times. Therefore, self-assembled monolayer using thiourea which is cheaper than thioctic acid and 3-mercaptopropionic acid is a good alternative for biosensor applications when SAMs are used.
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http://dx.doi.org/10.1016/j.bios.2005.12.025DOI Listing
August 2006

Comparative study of controlled pore glass, silica gel and poraver for the immobilization of urease to determine urea in a flow injection conductimetric biosensor system.

Biosens Bioelectron 2004 Mar;19(8):813-21

Biophysics Research Unit of Biosensors and Biocurrents, Prince of Songkla University, Hat Yai, Songkhla 90112, Thailand.

This study compared the responses of three enzyme reactors containing urease immobilized on three types of solid support, controlled pore glass (CPG), silica gel and Poraver. The evaluation of each enzyme reactor column was done in a flow injection conductimetric system. When urea in the sample solution passed though the enzyme reactor, urease catalysed the hydrolysis of urea into charged products. A lab-built conductivity meter was used to measure the increase in conductivity of the solution. The responses of the enzyme reactor column with urease immobilized on CPG and silica gel were similar and were much higher than that of Poraver. Both CPG and silica gel reactor columns gave the same limit of detection, 0.5 mM, and the response was still linear up to 150mM. The analysis time was 4-5 min per sample. The enzyme reactor column with urease immobilized on CPG gave a slightly better sensitivity, 4% higher than the reactor with silica gel. The life time of the immobilized urease on CPG and silica gel were more than 310h operation time (used intermittently over 7 months). Good agreement was obtained when urea concentrations of human serum samples determined by the flow injection conductimetric biosensor system was compared to the conventional methods (Fearon and Berthelot reactions). These were statistically shown using the regression line and Wilcoxon signed rank tests. The results showed that the reactor with urease immobilized on silica gel had the same efficiency as the reactor with urease immobilized on CPG.
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http://dx.doi.org/10.1016/j.bios.2003.08.007DOI Listing
March 2004