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Zn.sup.2+ and Cu.sup.2+ related to transition metal ions present in foods play essential roles in the health of human and animal metabolism. However, the excess of these ions contaminates foods and causes many kinds of diseases. In recent years, designing chemosensors for detection of the two targets has been widespread but is still a great challenge for practical application. In this study, by reducing expenses, simplifying analytical procedures, and enabling multifunctions, a functional chemosensor was proposed by using tetraphenylethylene derivative (H.sub.4tcbpe) which could selectively and sensitively response to Zn.sup.2+ and Cu.sup.2+. H.sub.4tcbpe can be used to detect Zn.sup.2+ with fluorescence enhancement based on aggregation induced emission effect, while fluorescence of H.sub.4tcbpe can be quenched by Cu.sup.2+ due to the disassembly of H.sub.4tcbpe aggregates in a solvent/nonsolvent binary mixture of EtOH and H.sub.2O. Fluorophotometry, UV-Vis, and SEM were used to characterize behavior of the fluorescence sensor. In this work, the detection in liquid solutions was conducted, and a fluorescent test pen for the assay of Zn.sup.2+ and Cu.sup.2+ on a piece of filter paper was fabricated. The proposed fluorescent test pen contained H.sub.4tcbpe as a 'fluorescent probe ink' and made it possible to write words on the area of a filter paper spiked with solutions with different concentrations of Zn.sup.2+ and Cu.sup.2+. The detection limits for Zn.sup.2+ and Cu.sup.2+ are 43 nM and 0.5 [mu]M, respectively. This fluorescent sensor was applied to sense ions in black fungus samples. The proposed sensor could successfully detect Zn.sup.2+ and Cu.sup.2+, and the results were in agreement with the data from inductively coupled plasma mass spectrometry, which indicated the reliability of the proposed sensor for applications in the real samples., Author(s): Xiujuan Qiao [sup.1] [sup.2] , Gengjia Chen [sup.1] , Tianli Yue [sup.1] , Qinglin Sheng [sup.1] Author Affiliations: (1) grid.412262.1, 0000 0004 1761 5538, College of Food Science and [...]

A novel, simple, and low-cost spray painting technique has been developed for the fabrication of microfluidic paper-based devices. The devices that we developed utilize aerosol spray paint to build hydrophobic barriers and employ a hole puncher to obtain paper-based patterned layers and paper dots without using any specialized instruments (e.g., without a laser cutter). The entire manufacturing process is extremely simple, inexpensive, and rapid, which means that it can be applied broadly. Furthermore, the application of the device to iron detection was demonstrated. A linear relationship between the colour value and the iron concentration was observed from 0 to 0.02 g/L. The developed microfluidic paper-based device for iron detection exhibited a low detection limit (0.00090 g/L), good selectivity, and acceptable recovery. Key words: microfluidic paper-based device, spray painting, colorimetry, iron. Nous avons mis au point une nouvelle technique de pulverisation de peinture simple et peu couteuse pour fabriquer des dispositifs microfluidiques a base de papier. A l'aide ces dispositifs, nous avons employe de la peinture en aerosol pour fabriquer des barrieres hydrophobes et, au moyen d'un poincon, nous avons pu obtenir des couches a motifs en papier et des rondelles de papier sans avoir recours a des instruments specialises (p. ex., sans dispositif de coupe au laser). Tout le processus de fabrication est extremement simple, rapide et peu couteux, ce qui permet son application a grande echelle. Par ailleurs, nous avons demontre l'application du dispositif a la detection du fer. Nous avons observe une relation lineaire entre l'intensite de la couleur et la concentration du fer dans l'intervalle de 0 a 0,02 g/L. Le dispositif microfluidique a base de papier employe applique a la detection du fer a montre une faible limite de detection (0,00090 g/L), une bonne selectivite et un taux de recuperation acceptable. [Traduit par la Redaction] Mots-cles : dispositif microfluidique a papier, peinture en aerosol, colorimetrie, fer., Introduction Microfluidic paper-based analytical devices ([mu]PADs) have emerged at the intersection of engineering, physics, chemistry, biochemistry, nanotechnology, and biotechnology, with practical applications in the design of systems in which low [...]

An ion-selective potentiometric sensor with an ionophore is developed based on the ion associate of artificial food colorant E133 and a cetylpyridinium cation. The main electroanalytical parameters of the sensor are evaluated: linearity range of the response, pH effect, and the effect of temperature on the electrode performance and selectivity. The sensor is used to determine E133 in the Powerade beverage. The accuracy of the determination is confirmed by an extraction-photometric method. Keywords: ion-selective potentiometric sensor, E133 colorant, Powerade beverage DOI: 10.1134/S1061934811010139, Artificial food colorants (AFCs) are widely used in the production of foods (beverages, confectionery, sweets, etc.) to give them necessary consumer properties [1]. The use of AFCs is based on [...]

Abstract: The present work describes the design and synthesis of simple colorimetric chemosensors based on Schiff-base for highly selective sensing of cyanide and fluoride ions. The chemosensor S2, containing an [...]

Cabergoline (CAB) is an ergot alkaloid derivative with dopamine agonist activity. In this work for the first time the electrocatalytic oxidation of CAB was carried out with nickel nanoparticles-modified carbon paste electrode using cyclic voltammetry, chronoamperometry, chronocoulometry and amperometry methods. At first, nickel nanoparticles were synthesized by non-aqueous polyol method and these nanoparticles were mixed with graphite powder to form modified carbon paste electrode. The resulting modified electrode was characterized by scanning electron microscope images. In the presence of 0.1 M NaOH a good redox behavior of the Ni(III)/Ni(n) couple at the surface of the electrode can be observed. CAB was successfully oxidized at the surface of the modified electrode. The electrocatalytic oxidation peak current of this drug was linearly dependent on its concentration. The proposed sensor exhibited a high sensitivity and was successfully applied for the determination of CAB in real samples. Keywords: electrocatalytic oxidation, nickel nanoparticles, non-aqueous polyol method, cabergoline DOI: 10.1134/S1061934816030126, Cabergoline 1-[(6-allyergoline-8β-yl)-carbonyl] 1-[3-(dimethylamino)propyl]-3-ethyl urea (Scheme) is a dopamine agonist licensed for the treatment of Parkinson's disease as adjunctive treatment with levodopa plus a dopa-decarboxylase inhibitor in patients effected by on-off [...]

The main analytical characteristics of electrical, electrochemical, and thermometric sensors in the detection of vapors and traces of explosives and accompanying substances are compared. The limits of detection, sensitivity, sensor setting time (response speed) and, recovery time after exposure to analytes, and the selectivity of sensors are discussed. The efficiency of using nanodimensional structures in the sensing elements of sensors is investigated. Keywords: explosives, electrical, electrochemical, and thermometric sensors, nanostructured sensing element DOI: 10.1134/S1061934816030023, Electrical, electrochemical, and thermometric sensors are promising gas-analytical devices for the detection of explosives and accompanying substances (EASs) [1-3], especially using nanodimensional structures [4, 5]. The prospects of these sensors [...]

A colorimetric sensor is proposed for the determination of cobalt. It is prepared by immobilizing 1-(2-pyridylazo)-2-naphthol (PAN) in an optically transparent polymethacrylate matrix. The conditions for determining cobalt by the proposed colorimetric sensor are found in the study of the complexation of cobalt with a PAN-modified polymethacrylate matrix. The determination is based on the interaction of the sensor with a cobalt solution at pH 4 for 5 min, followed by the measurement of absorbance at 620 nm. The sensor ensures the determination of 0.05-0.50 mg/L of cobalt with the detection limit 0.03 mg/L. It is demonstrated that the sensor can be used for the determination of cobalt in the Cyanocobalamin medical preparation and potable water. Keywords: cobalt, immobilized reagent, polymethacrylate matrix, colorimetric sensor, solid-phase spectrophotometry DOI: 10.1134/S1061934815120060, Cobalt is a vital trace element with potential toxicity; the strict control of its concentration in the environment is required. Cobalt is a part of vitamin [B.sub.12] (cyanocobalamin), which is [...]

A microfluidic system of capillary electrophoresis with electrochemical detection is developed. The process of manufacturing a chip based on polydimethylsiloxane and glass for the determination of electroactive compounds is described. We studied the possibilities of the treatment of the chip channel surface in a gas discharge with sodium dodecyl sulfate, sodium deoxycholate, and an ionic liquid of 1-dodecyl-3-trimethylimidazolium chloride, used as additives to the background electrolyte. It was found that the developed microfluidic system can be used for the determination of polyphenolic antioxidants in green tea and red wine. Keywords: microfluidic systems, capillary electrophoresis, amperometric detection, polyphenolic antioxidants DOI: 10.1134/S1061934815060118, The number of developments in microfluidic analytical systems (MFAS) is actively growing. The advantages of MFAS are rapidity, low consumption of samples and reagents, portable equipment, and the relative simplicity [...]

The main analytical characteristics of optical chemical sensors for detecting the vapors and microparticles of explosives and associated substances are compared. The limits of detection, sensitivity, sensor setting time (response speed) and recovery time after the action of an analyte, and the selectivity of fluorescence sensors, chemiluminescence sensors, surface-enhanced Raman sensors, surface plasmon resonance sensors, absorption integrated optical waveguide sensors, waveguide interferometric sensors, and ring resonator based sensors. The effectiveness of the use of nanosized structures and bio- and nanostructured specific coatings in optical sensors is analyzed. Keywords: explosives, optical chemical sensors, bio- and nanostructured specific coatings DOI: 10.1134/S1061934814070041, A search for explosive bulks and mines (EBMs) is among the main tasks of safety precautions. In the solution of this problem with the aid of optical chemical sensors, the [...]

We propose a simple microfluidic device for protein preconcentration based on the electrokinetic trapping principle. It comprises a narrow Nation strip that is simply cut from a commercial membrane and is integrated into a molded poly(dimethylsiloxane) (PDMS) microfluidic structure using a guiding channel. Mechanically clamping the PDMS/Nation assembly with a glass substrate results in a rapid prototypable, leak-tight, and easily disposable device. Our device preconcentrates negatively charged fluorescent proteins located at the anodic microfluidic compartment side of the Nation strip within a few minutes and up to a concentration factor of [10.sup.4]. Moreover, we present a numerical study of the preconcentration effect by solving the coupled Poisson, Nernst-Planck, and Navier Stokes equations for our type of device, which provides microscopic insight into the mechanism of preconcentration. The electrical field across the ion-permselective Nation generates concentration polarization, i.e., ion depletion at the anodic side and ion enrichment at the cathodic side for both types of ions, with a local excess of mobile positive ions in the depleted concentration polarization zone, inducing a nonequilibrium electrical double layer in close proximity to the Nation membrane. A voltage difference applied over the anodic compartment is used to generate the electrophoretic flow velocity of the negatively charged tracer biomolecules. This, in combination with the electroosmotic flow in the opposite direction, which originates from the fixed charges on the channel walls and the induced space charge near the membrane, provides the basis for the local preconcentration of the negative tracer biomolecules. 10.1021/ac102149f

A spectroelectrochemical sensor was demonstrated for an organic compound whose oxidation proceeds through an electron transfer--chemical reaction-electron transfer (ECE) mechanism to generate new chemical species that are used for detection by fluorescence. The polycyclic aromatic hydrocarbon 1-hydroxypyrene (1-PyOH) served as a representative model analyte. The spectroelectro-chemical properties of 1-PyOH in solution were explored with an optically transparent thin layer electrode. Electrochemical oxidation of 1-PyOH under acidic conditions proceeds via the ECE mechanism to a diquinonepyrene, which shows reversible electrochemistry and fluoresces at 425 nm in its reduced form, dihydroxypyrene. The sensor consisted of a tin-doped indium optically transparent electrode coated with a Nation thin-film (20 nm) that rapidly preconcentrated the analyte at the sensor surface. Fluorescence in the film was excited by the evanescent wave from attenuated total reflection spectroscopy. Electrochemical modulation of dihydroxypyrene fluorescence at 425 nm in the 500 to -200 mV (vs Ag/AgCl) potential range was used for indirect detection of 1-PyOH. The spectroelectrochemical sensor calibration curve had a range of 5 x [10.sup.-9] to 1 x [10.sup.-6] M with a calculated detection limit of 1 x [10.sup.-9] M. 10.1021/ac101883a

We propose a highly sensitive chemical sensor by functionally coating a zeolite film on the external surface of an optical microsphere. Using the perturbation theory, a model is developed to calculate sensor sensitivity and analyze the impact of the zeolite film thickness. The quality factor and detection limit are also investigated by using an approximate model. Simulations show that a zeolite coating can effectively increase sensitivity. The results provide physical insights for the design and optimization of various parameters for desired sensor performance. OCIS codes: 140.3948, 280.4788, 140.4780, 230.5750.

The concept of triggered polycatenated DNA scaffolds has been elegantly introduced into ultrasensitive biosensing applications by a combination of rolling circle amplification (RCA) and DNAzyme amplification. As compared to traditional methods in which one target could only initiate the formation of one circular template for RCA reaction, in the present study two species of linear single-stranded DNA (ssDNA) monomers are self-assembled into mechanically interlocked polycatenated nanostructares on capture probe-tagged magnetic nanoparticles (MNPs) only upon the introduction of one base mutant DNA sequence as initiator for single-nucleotide polymorphisms (SNPs) analysis. The resultant topologically polycatenated DNA ladder is further available for RCA process by using the serially ligated circular DNA as template for the synthesis of hemin/G-quadruplex HRP-mimicking DNAzyme chains, which act as biocatalytic labels for the luminol-[H.sub.2][O.sub.2] chemiluminescence (CL) system. Notably, the problem of high background induced by excess heroin itself is circumvented by immobilizing the biotinylated RCA products on streptavidin-modified MNPs via biotin--streptavidin interaction. Similarly, a universal strategy is contrived by substitutedly employing aptamer as initiator for the construction of polycatenated DNA scaffolds to accomplish ultrasensitive detection of proteins based on structure-switching of aptamer upon target binding, which is demonstrated by using thrombin as a model analyte in this study. Overall, with two successive amplification steps and one magnetic separation procedure, this flexible biosensing system exhibits not only high sensitivity and specificity with the detection limits of SNPs and thrombin as low as 71 aM and 6.6 pM, respectively, but also excellent performance in real human serum assay with no PCR preamplification for SNPs assay. Given the unique and attractive characteristics, rids study illustrates the potential of DNA nanotechnology in bioanalytical applications for both fundamental and practical research. 10.1021/ac1021198

A low-cost yet highly sensitive colorimetric sensor array for the detection and identification of toxic industrial chemicals (TICs) has been developed. The sensor consists of a disposable array of cross-responsive nanoporous pigments whose colors are changed by diverse chemical interactions with analytes. Clear differentiation among 20 different TICs has been easily achieved at both their IDLH (immediately dangerous to life or health) concentration within 2 min of exposure and PEL (permissible exposure limit) concentration within 5 min of exposure with no errors or misclassifications. Detection limits are generally well below the PEL (in most cases below 5% of PEL) and are typically in the low ppb range. The colorimetric sensor array is not responsive to changes in humidity or temperature over a substantial range. The printed arrays show excellent batch to batch reproducibility and long shelf life (greater than 3 months). 10.1021/ac1020886

A portable surface-enhanced Raman scattering (SERS) sensor is developed and applied to simultaneous detection of aniline and phenol derivatives in a label-free way with an electrostatic preconcentration technique to amplify the signals. A SERS-active substrate, silver-electrodeposited screen-printed electrodes (Ag-SPEs), is used for qualification and quantification of polar organic pollutants. Observation of SERS spectra at different potentials indicates that polar pollutants are selectively adsorbed on the Ag-SPEs at a given potential, suggesting that Ag-SPEs could selectively attract polar pollutants to an oppositely charged electrode at different potentials. Optimum SERS-active substrate was obtained when a potential of-0.15 V vs Ag/AgC1 was applied on the SPEs in 0.1 M AgN[O.sub.3] solution for 10 min. Moreover, the effects of experimental variables such as the electrodeposition time and potential of Ag and preconcentration time of polar molecules on the SERS signals are presented. Under optimum conditions and with a 785 nm laser, the method is effective over a wide range of concentration (1 nM to 1 [micro]M) for aniline and phenol derivatives. The novel method described herein presents a new detection regime for environmental pollutant analysis and also demonstrates simultaneous multiplexed detection of polar organic pollutants using convenient Ag-SPEs. 10.1021/ac101812x

Electrochemical mapping of neurotransmitter concentrations on a chip promises to be an interesting technique for investigating synaptic release in cellular networks. In here, we present a novel chip-based device for the detection of ueurotransmitter fluctuations in real-time. The chip features an array of plane-parallel nanocavity sensors, which strongly amplify the electrochemical signal. This amplification is based on efficient redox cycling via confined diffusion between two electrodes inside the nanocavity sensors. We demonstrate the capability of resolving concentration fluctuations of redox-active species in a microfluidic mixing gradient on the chip. The results are explained by a simulated concentration profile that was calculated on the basis of the coupled Navier-Stokes and convection-diffusion equations using a finite element approach. 10.1021/ac1013871

Adsorption of the elongated human plasma fibrinogen (HPF) and globular human serum albumin molecules on a titanium-based surface is monitored by analyzing permittivity and optical roughness of protein-modified surfaces by using a diffractive optical element (DOE)-based sensor and variable angle spectro-ellipsometry (VASE). Both DOE and VASE confirmed that fibrinogen forms a thicker and more packed surface adlayer compared to a more porous and weakly adsorbed albumin adlayer. A linear relation of the permittivity ([epsilon]) and dielectric loss ([epsilon]') was found for some of the dry titanium-doped hydrocarbon (TDHC) surfaces with excellent HPF adsorption ability. We discuss some aspects of TDHC's aging and its possible effects on fibrinogen adsorption. [c] 2010 Optical Society of America OCIS codes: 050.1970, 240.2130, 240.5770, 170.3890, 170.1850.

A ribonucleic acid (RNA) sensor based on hybridization of its peptide nucleic acid (PNA) molecule with a target RNA oligomer of the internal ribosome entry site sequence specific to the hepatitis C virus (HCV) and the electrochemical impedance detection is described. This RNA is one of the most conservative molecules of the whole HCV RNA genome. The ammonium ion terminated PNA molecule was immobilized via its host--guest interactions with the diaza crown ring of 3-thiophene-acetamide-diaza-18-crown-6 synthesized by a simple two-step method, which forms a well-defined self-assembled monolayer (SAM) on gold. Hybridization events of the probe PNA with the target RNA were monitored by measuring charge-transfer resistances for the Fe[[(CN).sub.6].sup.3-/4-] redox probe using Fourier transform electrochemical impedance spectroscopy. The ratio of the resistances of the SAM-covered electrode measured before and after hybridization increased linearly with log[RNA] in the rat liver lysate with a detection limit of about 23 pM. 10.1021/ac1019232

Liquid-phase operation of resonant cantilevers vibrating in an out-of-plane flexural mode has to date been limited by the considerable fluid damping and the resulting low quality factors (Q factors). To reduce fluid damping in liquids and to improve the detection limit for liquid-phase sensing applications, resonant cantilever transducers vibrating in their in-plane rather than their out-of-plane flexural resonant mode have been fabricated and shown to have Q factors up to 67 in water (up to 4300 in air). In the present work, resonant cantilevers, thermally excited in an in-plane flexural mode, are investigated and applied as sensors for volatile organic compounds in water. The cantilevers are fabricated using a complementary metal oxide semiconductor (CMOS) compatible fabrication process based on bulk micromachining. The devices were coated with chemically sensitive polymers allowing for analyte sorption into the polymer. Poly(isobutylene) (PIB) and poly(ethylene-eo-propylene) (EPCO) were investigated as sensitive layers with seven different analytes screened with PIB and 12 analytes tested with EPCO. Analyte concentrations in the range of 1-100 ppm have been measured in the present experiments, and detection limits in the parts per billion concentration range have been estimated for the polymer-coated cantilevers exposed to volatile organics in water. These results demonstrate significantly improved sensing properties in liquids and indicate the potential of cantilever-type mass-sensitive chemical sensors operating in their in-plane rather than out-of-plane flexural modes. 10.1021/ac1010102

This paper describes a highly sensitive and selective chemical sensor using living cells (Xenopus laevis oocytes) within a portable fluidic device. We constructed an odorant sensor whose sensitivity is a few parts per billion in solution and can simultaneously distinguish different types of chemicals that have only a slight difference in double bond isomerism or functional group such as --OH, --CHO and -C/=O/-. We developed a semiautomatic method to install cells to the fluidic device and achieved stable and reproducible odorant sensing. In addition, we found that the sensor worked for multiple-target chemicals and can be integrated with a robotic system without any noise reduction systems. Our developed sensor is compact and easy to replace in the system. We believe that the sensor can potentially be incorporated into a portable system for monitoring environmental and physical conditions. fluidic channel | odorant receptor | robot | Xenopus oocyte doi/ 10.1073/pnas.1004334107

We introduce here a new class of BODIPY-based [Ca.sup.2+] indicators which can be derivatized with biological ligands that permit the localization of the indicators in living cells. The underivatized BODIPY-based [Ca.sup.2+] indicator (BOCA-l) shows a 250-fold increase in fluorescence intensity upon [Ca.sup.2+] binding. We also prepared its [O.sup.6]-benzylguanine (BG) derivative, BOCA1-BG, which can be covalently and specifically linked to SNAP-tag fusion proteins in living cells. The indicator retains its properties as a highly sensitive [Ca.sup.2+] indicator after conjugation to proteins, displaying a 180-fold increase in fluorescence intensity upon [Ca.sup.2+] binding. We further demonstrated that BOCA-1-BG through reaction with localized SNAP-tag fusion proteins can be used to sense changes in [Ca.sup.2+] concentrations in the nuclei and in the cytosol of live CHO-K1 cells. The high sensitivity of the indicator together with the possibility to selectively couple it to proteins of interest makes it a powerful tool for measuring local changes in [Ca.sup.2+] concentrations in living cells. 10.1021/ac100741t

We report a turn-on sensor framework with enhanced vapor sensitivity by increasing the sensor's response dynamic range via rational design of the sensor formulation. Using a fluorescent dye as the reporter, our approach begins by reducing sensor background fluorescence through the use of selected quenchers. Analyte interaction induces the onset of emission by interrupting the quenching interaction, thereby turning on the sensor. We demonstrate over an order of magnitude increase in vapor sensitivity for dimethyl methylphosphonate (a Satin simulant) detection using a sensor containing inorganic oxides as a quencher for Nile Red dye. This approach was also used to develop a new sensor with improved sensitivity for methyl benzoate (a hydrolysis byproduct of cocaine, used to |rain drug-sniffing dogs). By generalization, additional candidate quenchers for Nile Red were identified based on Lewis acid/base interactions. This framework can be applied in parallel with other amplification strategies including mass transport incentive, one-analyte-to-multiple-reporter schemes or signal lasing to further increase sensor response amplitude. 10.1021/ac1007859

Mesoporous SBA-15 silica is an excellent support for constructing fluorescent surface sensors. In this letter, we reported a two-step surface reaction involved strategy to construct efficient fluorescent surface sensors for metal ions by clicking fluoroionophores onto azide-functionalized SBA-15. Our experimental results indicate that such a strategy exhibits an obviously higher loading efficiency within commercial SBA-15 than a previously reported strategy. As a proof-of-concept, a newly designed alkyne-functionalized [Hg.sup.2+] fluoroionophore was grafted onto SBA-15 to form a fluorescent [Hg.sup.2+] surface sensor. It shows improved sensitivity and selectivity than the fluoroinnophore itself working in the solution phase with a detection limit of 2.0 x [10.sup.-8] M for [Hg.sup.2+]. 10.1021/ac101305e

A novel and portable fluorescent sensor that integrates an immunochromatographic test strip assay (ITSA) with a quantum dot (QD) label and a test strip reader was described in this study for simple, rapid, and sensitive biomonitoring of an organophosphorus pesticide metabolite. The principle of this sensor is based on a competitive immunoreaction that was performed on an immunochromatographic test strip, where analytes compete with competitors (QD-conjugated analogs) to bind to antibodies on a test zone. Captured QDs serve as signal vehicles for fluorescent readout. In this work, 3,5,6-trichloropyridinol (TCP) is used as a model analyte to demonstrate the performance of the immunosensor. QD-TCP conjugates were synthesized and characterized with X-ray photoelectron spectroscopy (XPS) and fluorescence spectroscopy. Some parameters (e.g., the amount of QD-modified TCP and immunoreaction time) that govern sensitivity and reproducibility of ITSA were optimized. Under optimal conditions, the sensor has a wide dynamic range and is capable of detecting a minimum 1.0 ng/mLTCP standard analyte in 15 min. The sensor has been successfully applied for detection of TCP spiked in rat plasma with average recovery of 102.0%. Results demonstrate that this sensor provides a rapid, clinically accurate, and quantitative tool for TCP detection and shows great promise for in-field and point-of-care (POC) quantitative testing and screening for metabolite biomarkers, e.g., TCP, for humans exposed to pesticides. 10.1021/ac100260m

A double covalent coupling method for the fabrication of a highly sensitive and reusable electrogenerated chemiluminescence (ECL) chemical sensor for the detection of tertiary amines and ECL aptamer-based (ECL-AB) biosensor for the detection of cocaine is reported. The ECL sensors were constructed by covalent coupling of amino-containing Ru[(bpy).sub.3.sup.2+] derivatives (Rul, Ru[(bpy).sub.3.sup.2+] = tris(2,2'-bipyridyl)ruthenium(II)) or cocaine aptamerRu1 to the surface of a paraffin-impregnated graphite electrode that had been covalently modified with a monolayer of 4-aminobenzene sulfonic acid via electrochemical oxidations. ECL performance of the newly developed chemical sensors was evaluated using trin-propylamine (TPrA) and metoclopramide (MCP) as model analytes. The sensors exhibited excellent sensitivity, stability, and reproducibility with a detection limit of 30 nM for TPrA and 2.0 nM for MCP, and relative standard deviations (RSDs) of 2.1% over 90 cyclic potential cycles (0 to 1.50 V vs Ag/AgCI) and 2.6% over 45 cycles (0.60 to +1.30 V vs Ag/AgCI) at 400 mV/s for 50 nM TPrA and 200 nM MCP, respectively. For the ECL-AB biosensor, it showed an extremely low detection limit of 10 pM for cocaine, and offered a good selectivity toward cocaine, heroin, and caffeine. This detection limit was about 4-6 orders of magnitude lower than that reported on the basis of alternating current (AC) voliammetry and optical aptamer-based cocaine biosensors. Additionally, the ECL-AB biosensor was highly reusable (RSD = 2.8%, n = 7) and possessed long-term storage stability (96.8% initial ECL recovery over 21 days storage). A binding constant of 4.6 [+ or -] 0.3 X [10.sup.9] [M.sup.-1] between cocaine and its aptamer was estimated using an ECL based Langmuir isotherm approach. Wide ranging applications of the presently reported strategy in fabricating various chemical sensors or biosensors are expected. 10.1021/ac9029289

We developed and characterized a Fabry--Perot (FP) sensor module based micro gas chromatography ([micro]GC) detector for multipoint on-column detection. The FP sensor was fabricated by depositing a thin layer of metal and a layer of gas-sensitive polymer consecutively on the endface of an optical fiber, which formed the FP cavity. Light partially reflected from the metal layer and the polymer--air interface generated an interference spectrum, which shifted as the polymer layer absorbed the gas analyte. The FP sensor module was then assembled by inserting the FP sensor into a hole drilled in the wall of a fused-silica capillary, which can be easily connected to the conventional gas chromatography (GC) column through a universal quick seal column connector, thus enabling on-column real-time detection. We characterized the FP sensor module based [micro]GC detector. Sensitive detection of various gas analytes was achieved with subnanogram detection limits. The rapid separation capability of the FP sensor module assembled with both single- and tandem-column systems was demonstrated, in which gas analytes having a wide range of polarities and volatilities were well-resolved. The tandem-column system obtained increased sensitivity and selectivity by employing two FP sensor modules coated with different polymers, showing great system versatility. 10.1021/ac902956d

A ubiquitous electrochemical sensor which can detect pollutants in nonconducting aqueous solutions is prepared using a triple layer design, comprising a polyelectrolyte entrapped within micrometer-length nanochannels and sandwiched between two nanometer-thick electrode layers. Replacement of the polyelectrolyte with an enzyme-polyelectrolyte mixture within the nanochannels confers excellent biosensing characteristics. Its superior analytical performance of quantitating copper ions and formaldehyde at trace levels without additional sample treatment steps is demonstrated in freshwater samples derived from a local reservoir. 10.1021/ac100776p

We have designed fluorescent nanosensors based on ion-selective optodes capable of detecting small molecules. By localizing the sensor components in a hydrophobic core, these nanosensors are able to monitor dynamic changes in concentration of the model analyte, glucose. The nanosensors demonstrated this response in vitro and also when injected subcutaneously into mice. The response of the nanosensors tracked changes in blood glucose levels in vivo that were comparable to measurements taken using a glucometer. The development of these nanosensors offers an alternative, minimally invasive tool for monitoring glucose levels in such fields as diabetes research. Furthermore, the extension of the ion-selective optode sensor platform to small molecule detection will allow for enhanced monitoring of physiological processes. 10.1021/ac100042e

A new strategy for assessing cell surface carbohydrates and P-glycoprotein (P-gp) expression status and quantifying the cell numbers with an electrochemical immunoassay was designed. In order to construct the base of the cytosensor, a novel 3-D architecture was initially fabricated by combining nitrogen-doped carbon nanotubes, thionine, and gold nanoparticles via a simple layer-by-layer method. The formed architecture provided an effective matrix for concanavalin A (Con A) binding and made the immobilized Con A hold high stability and bioactivity. On the basis of the specific recognition of cell surface mannosyl groups to Con A, the Con A/3-D architecture interface showed a predominant capability for cell capture. With another coupled signal amplification based on a enzymatic catalytic reaction of HRP toward the oxidation of thionine by the [H.sub.2][O.sub.2], which was induced by two-step immunoreactions, the proposed cytosensor showed an excellent analytical performance for the detection of HeLa cells ranging from 8.0 x [10.sup.2] to 2.0 x [l0.sup.7] cells [mL.sup.-1] with a limit of detection of 500 cells [mL.sup.-1]. Moreover, with the use of preblocking procedures, the mannosyl groups and P-gp on single HeLa cell could be further detected to be (4 [+ or -] 2) x [10.sup.10] molecules of mannose moieties and 8.47 x [10.sup.6] molecules of P-gp. This strategy offers great promise for sensitive detection of cancer cells and cell surface receptors and thus may help improve cancer diagnosis and treatment. 10.1021/ac9026127

Combining nanomaterials and biomolecule recognition units is promising in developing novel clinic diagnostic and protein analysis techniques. In this work, a highly sensitive and specific fluorescence resonance energy transfer (FRET) aptasensor for thrombin detection is developed based on the dye labeled aptamer assembled graphene. Due to the noncovalent assembly between aptamer and graphene, fluorescence quenching of the dye takes place because of FRET. The addition of thrombin leads to the fluorescence recovery due to the formation of quadruplex-thrombin complexes which have weak affinity to graphene and keep the dyes away from graphene surface. Because of the high fluorescence quenching efficiency, unique structure, and electronic properties of graphene, the graphene aptasensor exhibits extraordinarily high sensitivity and excellent specificity in both buffer and blood serum. A detection limit as low as 31.3 pM is obtained based on the graphene FRET aptasensor, which is two orders magnitude lower than those of fluorescent sensors based on carbon nanotubes. The excellent performance of FRET aptasensor based on graphene will also be aseribed to the unique structure and electronic properties of graphene. 10.1021/ac9025384

We have developed a resistance-based chemical sensor (chemiresistor) for volatile organic compounds whose sensitivity can be reversibly increased over a range of nearly 2 decades by the application of tensile strain. This polymer-based sensor is comprised of Au-plated magnetic particles structured into conducting chains by the application of a magnetic field during the curing of the prepolymer resin. The resistance of this field-structured composite increases when an analyte vapor swells the polymer and reduces the contact pressure between partides. We have found that applying a tensile strain increases both the sensor resistance and sensitivity, as defined by its relative resistance change. This increase in sensitivity is a smooth, continuous function of the applied strain, and the effect is fully reversible. Sensitivity tuning enables the response curve of the sensor to be dynamically optimized for sensing analytes over a wide concentration range. 10.1021/ac902897e

We demonstrate a highly sensitive nano aptasensor for anthrax toxin through the detection of its polypeptide entity, protective antigen (PA toxin) using a PA toxin ssDNA aptamer functionalized single-walled carbon nanotubes (SWNTs) device. The aptamer was developed inhouse by capillary electrophoresis systematic evolution of ligands by exponential enrichment (CE-SELEX) and had a dissociation constant ([K.sub.d]) of 112 nM. The aptasensor displayed a wide dynamic range spanning up to 800 nM with a detection limit of I nM. The sensitivity was 0.11 per nM, and it was reusable six times. The aptasensor was also highly selective for PA toxin with no interference from human and bovine serum albumin, demonstrating it as a potential tool for rapid and point-of-care diagnosis for anthrax. 10.1021/ac902791q

Owing to their unique optical properties, quantum dots (QDs) with different colors have been applied for simultaneous detection of multiple analytes. However, the use of single QD for multiplex detection of analytes with single-molecule detection has not been explored. Here we report a single QD-based nanosensor for multiplex detection of HIV-1 and HIV-2 at single-molecule level in a homogeneous format. In this single QD-based nanosensor, the QD functions not only as a fluorescence pair for coincidence detection and as a fluorescence-resonance-energy-transfer (FRET) donor for FRET detection but also as a local nanoconcentrator which significantly amplifies the coincidence-related fluorescence signals and the FRET signals. This single-QD-based nanosensor takes advantage of a simple 'mix and detection' assay with extremely low sample consumption, high sensitivity, and short analysis time and has the potential to be applied for rapid point-of-care testing, gene expression studies, high-throughput screening, and clinical diagnostics. 10.1021/ac9026675

Traditional antibody-based affinity sensing strategies employ multiple reagents and washing steps and are unsuitable for real-time detection of analyte binding. Aptamers, on the other hand, may be designed to monitor binding events directly, in real-time, without the need for secondary labels. The goal of the present study was to design an aptamer beacon for fluorescence resonance energy transfer (FRET)based detection of interferon-gamma (IFN-[gamma])--an important inflammatory cytokine. Variants of DNA aptamer modified with biotin moieties and spacers were immobilized on avidin-coated surfaces and characterized by surface plasmon resonance (SPR). The SPR studies showed that immobilization of aptamer via the 3' end resulted in the best binding IFN-[gamma], ([K.sub.d] = 3.44 nM). This optimal aptamer variant was then used to construct a beacon by hybridizing fluorophore-labeled aptamer with an antisense oligonucleotide strand carrying a quencher. SPR studies revealed that IFN-[gamma] binding with an aptamer beacon occurred within 15 min of analyte introduction--suggesting dynamic replacement of the quencher-complementary strand by IFN-[gamma] molecules. To further highlight biosensing applications, aptamer beacon molecules were immobilized inside microfluidic channels and challenged with varying concentration of analyte. Fluorescence microscopy revealed low fluorescence in the absence of analyte and high fluorescence after introduction of IFN-[gamma]. Importantly, unlike traditional antibody-based immunoassays, the signal was observed directly upon binding of analyte without the need for multiple washing steps. The surface immobilized aptamer beacon had a linear range from 5 to 100 nM and a lower limit of detection of 5 nM IFN-[gamma]. In conclusion, we designed a FRET-based aptamer beacon for monitoring of an inflammatory cytokine--IFN-[gamma]. In the future, tiffs biosensing strategy will be employed to monitor dynamics of cytokine production by the immune cells. 10.1021/ac9025237

A new strategy for the fabrication of a sulfide sensor based on room-temperature phosphorescence (RTP) of PbO/ Si[O.sub.2] nanocomposite is proposed. The PbO/Si[O.sub.2] phosphor is prepared by a sol gel method, and it produces highly emissive broad-band RTP under the irradiation of UV light. The phosphorescence intensity of PbO/ Si[O.sub.2] nanocomposite could be quenched by sulfide, and the response behavior of the sensor is dependent on the value of pH of the solution. At pH 11.0, the sensor exhibits a linear response toward sulfide at the concentration range from 2.67 to 596 [micro]M. The detection limit for the sensor is estimated to be 0.138 pM (3 [sigma]), and the precision for five replication detections of 6 [micro]M sulfide is 1.82% (relative standard deviation). The color of the sensor and its phosphorescence intensity change obviously and could be observed with the naked eye when there was continuous addition of sulfide from the concentration of 50 [micro]M. The phosphorescence intensity of quenched PbO/Si[O.sub.2] phosphor can be recovered when dipping it into [H.sub.2][O.sub.2] solution, which demonstrates a good sulfide response characteristic of reusability. Furthermore, the sensor is easy to apply for trace hydrogen sulfide determination in the gas phase. 10.1021/ac921211

The lead ion ([Pb.sup.2+]) has been proven to induce a conformational change of K+-stabilized G-quadruplex DNAzyme and inhibit the peroxidase-like activity [Li, T.; Wang, E.; Dong, S. J. Am. Chem. Soc. 2009, 131, 15082-15083]. This provides a rationale for utilizing [Pb.sup.2+]-induced allosteric G-quadruplex DNAzyme to probe aqueous [Pb.sup.2+]. Here, we choose a common G-quadruplex DNAzyme named PS2.M to develop a novel [Pb.sup.2+] sensor with two detection means: colorimetry and chemiluminescence (CL). In the presence of [K.sup.+], PS2.M (with hemin as a cofactor) exhibits a superior DNAzyme activity and effectively catalyzes the [H.sub.2][O.sub.2]-mediated oxidation of 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) or luminol, which results in a color change or generates CL emission. Upon the addition of [Pb.sup.2+], [K.sup.+]-stabilized PS2.M is induced to convert to the [Pb.sup.2+]-stabilized structure with higher stability but lower DNAzyme activity, which is reflected by an obvious increase in DNA melting temperature but a sharp decrease in readout signal. This allows us to utilize PS2.M for quantitative analysis of aqueous [Pb.sup.2+] using the ABTS-[H.sub.2][O.sub.2] colorimetric system and luminol [H.sub.2][O.sub.2] CL system. In each case, the readout signal is linearly dependent on the logarithm of [Pb.sup.2+] concentration within a certain range. Nevertheless, two sensing systems provide different sensitivity for [Pb.sup.2+] analysis. With colorimetry, [Pb.sup.2+] can be detected at a level of 32 nM (~7 pph), whereas the detection limit of [Pb.sup.2+] is 1 nM (0.2 ppb) when utilizing the CL method. In addition to high sensitivity, the above sensing systems exhibit good selectivity for [Pb.sup.2+] over other metal ions. These results demonstrate the facility and effectivity of our introduced DNAzyme-based sensor for quantitative [Pb.sup.2+] analysis. 10.1021/ac902638v

In this paper, we present an innovative sensing nanomaterial for an interference localized surface plasmon resonance (iLSPR) sensor. The iLSPR is based on plasmonic gold nanoparticles with photonic thin-film muifilayers of porous aluminum oxide ([Al.sub.2][O.sub.3]) and aluminum (Al) on a substrate. With a controllable Wansparent [Al.sub.2][O.sub.3] layer and a highly reflective Al layer, our new nanomaterial was able to detect refractive index (RI) changes of the surrounding environment and the specific interaction of biomoleeules including biotin and avidin, 5-fluorouracil (5-FU) and its antibody, anti-5-fluorouracil (anti 5-FU), when the iLSPR surfaces were biologically functionalized. Our model nanostructure will open the way to display the plasmonic properties of other noble metal nanoparticles and to develop other functionally similar nanosensors, which could then be expanded into multiarrays. 10.1021/ac902008x

Optical fluorescence sol gel sensors have been developed for the detection of carbon dioxide gas in the 0.03-30% range with a detection limit of 0.008% (or 80 ppm) and a quantitation limit of 0.02% (or 200 ppm) C[O.sub.2]. Sol-gels were spin-coated on glass slides to create an organically modified silica-doped matrix with the 1-hydroxypyrene-3,6,8--trisulfonate (HPTS) fluorescent indicator. The luminescence intensity of the HPTS indicator (513 nm) is quenched by C[O.sub.2], which protonates the anionic form of HPTS. An ion pair technique was used to incorporate the lipophilic dye into the hydrophllic sol-gel matrix. Ti[O.sub.2] particles ( 10.1021/ac901890r

A new, highly sensitive and selective sensor for the electrochemical assay of Hg(II) by anodic stripping voltammetry has been developed, whereby a glassy carbon electrode is modified with a novel inorganic-organic hybrid nanocomposite, namely, bimetallic Au-Pt nanoparticles/organic nanofibers (labeled as Au-PtNPs/NFs). The sensor possesses a three-dimensional (3D) porous network nanoarchitecture, in which the bimetallic Au Pt NPs serving as metal NP-based microelectrode ensembles are homogenously distributed in the matrix of interlaced organic NFs. The surface structure and composition of the sensor were characterized by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Its electrochemical performance was systematically investigated. Our results show that such a newly designed, Au PtNPs/NF nanohybrid modified electrode provides remarkably improved sensitivity and selectivity for the stripping assay of Hg(II). The detection limit is found to be as low as 0.008 ppb (S/N = 3) that is much below the guideline value from the World Health Organization (WHO). Interferences from other heavy metal ions such as Cu(II), Cr(III), Co(II), Fe(II), Zn(II), and Mn(II) ions associated with mercury analysis are effectively inhibited. Toward the goal for practical applications, the sensor was further evaluated by monitoring Hg(II) in tap and river water specimens. 10.1021/ac901846a

We report a label-free fluorescent aptamer sensor for adenosine based on the regulation of malachite green (MG) fluorescence, with comparable sensitivity and selectivity to other labeled adenosine aptamer-based sensors. The sensor consists of free MG, an aptamer strand containing an adenosine aptamer next to an MG aptamer, and a bridging strand that partially hybridizes to the aptamer strand. Such a hybridization prevents MG from binding to MG aptamer, resulting in low fluorescence of MG in the absence of adenosine. Addition of adenosine causes the adenosine aptamer to bind adenosine, weakening the hybridization of the aptamer strand with the bridging strand, making it possible for MG to bind to the aptamer strand and exhibit high fluorescence intensity. Since this design is based purely on nucleic acid hybridization, it can be generally applied to other aptamers for the label-free detection of a broad range of analytes. 10.1021/ac9018473

Spectroelectrochemical sensors combine three modes of selectivity in a single device (electrochemistry, spectroscopy, and selective partitioning). A thin polymer film is coated onto the sensing platform in order to facilitate chemically selective transport to the electrode. The film is an essential part of the sensor because it provides an increase in selectivity and sensitivity by selectively pre-concentrating the analyte. Here, we report the next step in the characterization of partially sulfonated polystyrene-block-poly(ethylene-ran-butylene)block-polystyrene (SSEBS) films for the purpose of chemical sensing by examining the selectivity of the sensor fabricated with this novel thin film material. Binaw mixtures using model analytes were used to demonstrate the sensor's ability to detect an analyte in the presence of a direct interference. The binary mixtures consisted of Ru[(bpy).sub.3.sup.2+]/Fe[(CN).sub.6.sup.3-], Ru[(bpy).sub.3.sup.2+]/ Fe[(bpy).sub.3.sup.2+], and Ru[(bpy).sub.3.sup.2+]/Cu[(bpy).sub.2.sup.2+]. Demonstration of the selective partitioning mode using the Ru[(bpy).sub.3.sup.2+]/Fe[(CN).sub.6.sup.3-] mixture and absorption detection showed the SSEBS film's preference for Ru[(bpy).sub.3.sup.2+] over Fe[(CN).sub.6.sup.3-], and therefore, Fe[(CN).sub.6.sup.3-] did not interfere with the sensor's response to Ru[(bpy).sub.3.sup.2+]. Furthermore, the importance of the use of three modes together was demonstrated by analysis of the Ru[(bpy).sub.3.sup.2+]/Fe[(bpy).sub.3.sup.2+] and the Ru[(bpy).sub.3.sup.2+]/Cu[(bpy).sub.2.sup.2+] test mixtures, where both selection of a specific wavelength for absorption and selection of a specific potential window were required to reduce or eliminate the signal from the interference. Finally, analysis of the Ru[(bpy).sub.3.sup.2+]/Fe[(bpy).sub.3.sup.2+] test mixture was also demonstrated using fluorescence detection. 10.1021/ac901595b

This paper reports an amperometric nitric oxide (NO) microsensor based on a cone-shaped nanopore-platinized Pt working electrode. The senor was fabricated using the following procedure: (1) a parent nanodisk electrode was prepared by polishing an etched Pt wire (radius = 12.5 [micro]m; dimension of etched tip end point < 10 nm) embedded in a glass capillary, (2) the nanodisk Pt was further etched to produce a nanopore (pore opening radius < 1 [micro]m; pore depth ~30[micro]m), (3) the Pt base surface in the nanopore electrode was platinized electrochemically to improve the sensor sensitivity, and (4) silanization and further modification with the electropolymerized polymeric film [poly(5-amino-1-naphthol)] on the nanopore-platinized Pt electrode were carded out to obtain the sensor selectivity to NO. The analytical performance of the sensor was characterized. For example, a sensor with a pore opening radius of 797 nm exhibited a decent linear dynamic range (at least for 0.2-1.8 [micro]M), detection limit of < ~32 nM, response time ([t.sub.90%]) of < ~5 s, and sensitivity of 6.5 [+ or -] 0.02 pA/nM. This sensor was used successfully as a NO-selective probe tip in scanning electrochemical microscopy (SECM) to obtain a two-dimensional image of the local NO concentrations for an inlaid NO-emitting microdisk film (radius = 12.5 [micro]m) on a glass substrate. 10.1021/ac901552m

We report a highly sensitive electrochemical sensor for the detection of [Hg.sup.2+] ions in aqueous solution by using a thymine (T)-rich, mercury-specific oligonucleotide (MSO) probe and gold nanoparticles (Au NPs)-based signal amplification. The MSO probe contains seven thymine bases at both ends and a 'mute' spacer in the middle, which, in the presence of [Hg.sup.2+], forms a hairpin structure via the [Hg.sup.2+]-mediated coordination of T-[Hg.sup.2+]-T base pairs. The thiolated MSO probe is immobilized on Au electrodes to capture free [Hg.sup.2+] in aqueous media, and the MSO-bound [Hg.sup.2+]' can be electrochemically reduced to [Hg.sup.+], which provides a readout signal for quantitative detection of [Hg.sup.2+]. This direct immobilization strategy leads to a detection limit of 1 [micro] M. In order to improve the sensitivity, MSO probe-modified Au NPs are employed to amplify the electrochemical signals. Au NPs are comodified with the MSO probe and a linking probe that is complementary to a capture DNA probe immobilized on gold electrodes. We demonstrated that this Au NPs-based sensing strategy brings about an amplification factor of more than 3 orders of magnitude, leading to a limit of detection of 0.5 nM (100 ppt), which satisfactorily meets the sensitivity requirement of U.S. Environmental Protection Agency (EPA). This Au NPs-based [Hg.sup.2+] sensor also exhibits excellent selectivity over a spectrum of interference metal ions. Considering the high sensitivity and selectivity of this sensor, as well as the cost-effective and portable features of electrochemical techniques, we expect this Au NPs amplified electrochemical sensor will be a promising candidate for field detection of environmentally toxic mercury.

The spectroelectrochemical sensor uses thin, solid polyelectrolyte films as an essential element in its operation. In this work we explored the potential of partially sulfonated pelystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene (SSEBS) thin polymer films for chemicad sensing. Spectroscopic ellipsometry was used to measure optical and surface properties of the air-dried and hydrated material. SSEBS incorporates a relatively small amount of water (overall change of 25%) mainly determined by the complex dynamics of the film. The decrease in the refractive index after complete hydration of the film can be predicted based on the magnitude of swelling using effective medium approximation models. Adhesion of the material on various surfaces (glass, indium fin oxide, gold) was evaluated with the tape peeloff method. The abifity of the SSEBS material to preconcentrate cations was evaluated by cyclic voltammetry, absorbance, and luminescence measurements using model analytes (Ru(bpy)32+, phenosafranine, and rhodamine 6G). The detection limits of the sensor for Ru[(bpy).sub.3.sup.2+] under unoptimized conditions can be significantly improved if luminescence is used as the detection modality (DL = 5 x [10.sup.-10] M) instead of absorbance (DL = 5 x [10.sup.-7] M). Overall, the results demonstrate the effectiveness of the SSEBS material for spectro-electrochemical sensing.

Herein, a sensitive and selective sensor for biothiols based on the recovered fluorescence of the CdTe quantum dots (QDs)-Hg(II) system is reported. Fluorescence of QDs could be quenched greatly by Hg(II). In the presence of biothiols, such as glutathione (GSH), homocysteine (Hcy), and cysteine (Cys), however, Hg(II) preferred to react with them to form the Hg(II)--S bond because of the strong affinity with the thiols of biothiols rather than quenching the fluorescence of the QDs. Thus, the fluorescence of CdTe QDs was recovered. The restoration ability followed the order GSH > Hcy > Cys due to the decreased steric hindrance effect. A good linear relationship was obtained from 0.6 to 20.0 [micro]mol [L.sup.-1] for GSH and from 2.0 to 20.0 [micro]mol [L.sup.-1] for Cys, respectively. The detection limits of GSH and Cys were 0.1 and 0.6 [micro]mol [L.sup.-1], respectively. In addition, the method showed a high selectivity for Cys among the other 19 amino acids. Furthermore, it succeeded in detecting biothiols in the Hela cell.