Detection of surface antigens on living cells through incorporation of immunorecognition into the distinct positioning of cells with positive and negative dielectrophoresis

Rapid determination of surface antigens on cells is possible by immobilization of cells accumulated by positive dielectrophoresis (p-DEP) via effective surface immunoreactions and removal of unbound cells by negative DEP (n-DEP). The DEP device for cell manipulation comprises a microfluidic channel with an upper indium tin oxide (ITO) electrode and a lower ITO microband array electrode (band electrode) modified with an antibody. Cells with the surface antigen introduced into the channel immediately accumulated on the surface of the band electrode during p-DEP generated by the application of ac voltage between the ITO electrode and the band electrode to immobilize by the specific antibody. The removal of accumulated cells to the gap region during n-DEP was used for rapid estimation of the residual cells with a specific surface antigen. We demonstrate here that human promyelocytic leukemia cells with the surface antigen CD33 can be captured on a band electrode modified with anti-CD33 antibody. The time required for the determination of the surface antigen using this compelled accumulation of cells by p-DEP and the separation of unbound cells by n-DEP is decreased to 60 s compared to that required by a cell binding assay using microtiter plates (30 min). Furthermore, the present method for a novel cell binding assay does not require pretreatment such as target labeling or washing of unbound cells and thereby enhancing throughput in the clinic and in cytobiology studies.     

Nucleic acid-functionalized Pt nanoparticles: Catalytic labels for the amplified electrochemical detection of biomolecules

Nucleic acid-functionalized Pt nanoparticles (Pt-NPs) act as catalytic labels for the amplified electrochemical detection of DNA hybridization and aptamer/protein recognition. Hybridization of the nucleic acid-modified Pt-NPs with a sensing nucleic acid/analyte DNA complex associated with an electrode enables the amperometric, amplified, detection of the DNA by the Pt NP electrocatalyzed reduction of H2O2 (sensitivity limit, 1 x 10(-11) M). Similarly, the association of aptamer-functionalized Pt- NPs to a thrombin aptamer/thrombin complex associated with an electrode allowed the amplified, electrocatalytic detection of thrombin with a sensitivity limit corresponding to 1 x 10(-9) M.     

Anodic stripping voltammetry coupled on-line with inductively coupled plasma mass spectrometry: optimization of a thin-layer flow cell system for analyte signal enhancement

Parameters affecting analyte signal enhancement in anodic stripping voltammetry-inductively coupled plasma mass spectrometry (ASV-ICP-MS), using a thin-layer ASV cell and microconcentric nebulization (MCN), have been examined. Silver was used as a test analyte and was deposited at a glassy carbon working electrode. The MCN allowed use of solution flow rates that were beneficial to optimum electrolytic performance of the thin-layer cell. High analyte deposition efficiencies obtained with the thin-layer cell, combined with minimal sample consumption of the MCN, allowed substantial signal enhancement (>400 times higher than continuous nebulization level) to be obtained with 2-3 mL of sample and deposition times of less than 30 min. Signal enhancement was strongly influenced by the opposing effect of flow rate on the electrolytic deposition efficiency (deposition efficiency decreases with increasing flow rate) and on the quantity of analyte delivered to the cell (analyte mass throughput increases with increasing flow rate). Excellent linearity for stripping peak heights was demonstrated for a wide range of analyte deposition times and for peak heights and peak areas (r > 0.999) over a wide concentration range (25 ng/L-20 μg/L). Precision was good (RSD typically <3% for n = 3-6) except for a high Ag blank contributed to by corrosion of the counter electrode and by Ag diffusion from the reference electrode into the cell. Details of the flow manifold and ASV cells are discussed, along with relevant performance characteristics of the MCN.     

Atrazine sensor based on molecularly imprinted polymer-modified gold electrode

Molecularly imprinted polymers (MIP) have been elucidated to work as artificial receptors. In our present study, a MIP was applied as a molecular recognition element to a chemical sensor. We have constructed an atrazine sensor based on a MIP layer selective for atrazine and its electrochemical reduction on gold electrode. The atrazine sensor was fabricated by directly polymerizing the atrazine-imprinted polymer composed from methacrylic acid and ethylene glycol dimethacrylate onto the surface of a gold electrode. By introducing LiCl into the MIP, atrazine was reduced below -800 mV vs Ag/AgCl reference electrode, at pH 3. The cathodic current of atrazine depended on the concentration of atrazine at the range of 1-10 microM. The sensor exhibited a selective response to atrazine. A nonimprinted polymer-modified electrode did not show selective response to atrazine, thus implying that the imprinted polymer acts as recognition element of atrazine sensor.     

Enzyme-amplified amperometric sandwich test for RNA and DNA.

A one-step enzyme-amplified amperometric sandwich hybridization test for RNA and DNA is described. The test utilizes a carbon electrode, modified with a film of co-electrodeposited avidin and redox polymer; the redox polymer electrically "wiring" horseradish peroxidase (HRP) reaction centers upon contact. The film is made specific for the particular RNA or DNA sequence tested by conjugating its avidin with a biotinylated oligonucleotide, complementary to the assayed sequence. This oligonucleotide-modified redox polymer film, prepared prior to the test, forms the base of the sandwich. The center layer of the sandwich, added in the test, is the analyte RNA or DNA; its top is a second complemetary oligonucleotide, which is HRP-labeled, and is cohybridized in the test. The test consists of mixing the analyte DNA or RNA solution, the HRP-labeled oligonucleotide solution, and a hydrogen peroxide solution, immersing the base-layer carrying electrode applying a potential of 0 V versus Ag/AgCl, and measuring the H2O2 electroreduction current. Completion of the sandwich brings the HRP label into electrical contact with the redox polymer, converting the nonelectrocatalytic base layer into an electrocatalyst for the electroreduction of H2O2 to water. Flow of H2O2 electroreduction current when the electrode is poised near Ag/AgCl potential indicates the presence of the analyte RNA or DNA. The current density for the maximally sandwich-covered electrode was 250 microA cm(-2), exceeding more than a 100-fold the current density flowing upon nonspecific binding of the HRP-labeled oligonucleotide. High concentrations of irrelevant DNA and diluted serum did not interfere with the assay. When the electrodes were rotated in order to make the solution-phase mass transport rapid, the test was completed in approximately 30 min. The test was applied in probing for the presence of a 60-base E. coli mRNA sequence.     

Liposomes labeled with biotin and horseradish peroxidase: a probe for the enhanced amplification of antigen--antibody or oligonucleotide--DNA sensing processes by the precipitation of an insoluble product on electrodes

Liposomes labeled with biotin and the enzyme horseradish peroxidase (HRP) are used as a probe to amplify the sensing of antigen-antibody interactions or oligonucleotide-DNA binding. The HRP-biocatalyzed oxidation of 4-chloro-1-naphthol (1) in the presence of H2O2, and the precipitation of the insoluble product 2 on electrode supports, are used as an amplification route for the sensing processes. The anti-dinitrophenyl antibody (DNP-Ab) is sensed by a dinitrophenyl-L-cysteine antigen monolayer associated with an Au electrode. A biotinylated anti-IgG-antibody (Fc-specific) is linked to the antigen-DNP-Ab complex, and the biotin-labeled HRP-liposomes associate with the assembly through an avidin bridge. The biocatalyzed precipitation of 2 on the electrode increases the electron-transfer resistances at the electrode-solution interface or the electrode resistance itself. The binding events of the different proteins on the electrode and the biocatalyzed precipitation of 2 on the conductive support are followed by Faradaic impedance spectroscopy or constant-current chronopotentiometry. DNP-Ab concentrations as low as 1 x 10(-11) g x mL(-1) can be detected by this method. The labeled liposomes were also used for the amplified detection of DNA 3. The oligonucleotide 4, complementary to a part of the target DNA 3 that is a model nucleic acid sequence for the Tay-Sachs genetic disorder, is assembled on an Au electrode. Hybridization of the analyte 3 followed by the association of the biotin-tagged oligonucleotide 5 yields a three-component double-stranded assembly. Sensing of the analyte 3 is amplified by the association of avidin, the labeled liposomes, and the subsequent biocatalyzed precipitation of 2 on the electrodes. The DNA 3 is detected with a sensitivity that corresponds to 6.5 x 10(-13) M. Faradaic impedance spectroscopy and chronopotentiometry were employed to follow the stepwise assembly of the systems and the electronic transduction of the detection of the analyte DNA 3.     

Interdigitated array electrode as an alternative to the rotated ring-disk electrode for determination of the reaction products of dioxygen reduction

Electrochemical reduction of dioxygen in aqueous media can proceed to water, hydrogen peroxide, or a mixture of the two. The production of hydrogen peroxide, classically established with the rotated ring-disk electrode, can also be quantitatively assessed at interdigitated array (IDA) electrodes, where dioxygen is reduced at the set of microband generator electrodes and any H(2)O(2) produced is detected by its oxidation (back to O(2)) at the interdigitated set of microband collector electrodes. The sensitivity of the IDA for H(2)O(2) detection is higher owing to its more complete collection, and to the ensuing regeneration of O(2), which leads to an amplification of the generator currents. The production of H(2)O(2) is thus reflected both in the ratio of collector and generator electrode currents [the collection efficiency, coll(τ)] and in the ratio of the generator current with the collector potential on to that with it off [amplification factor, ampl(τ)]. The necessary theory for interpretation of the fraction ε of H(2)O(2) produced per dioxygen reduced is presented, based on conformal mapping techniques. Explicit equations are derived for ε at long times that are independent of the IDA dimensions and that can be used with any two-product electrochemical reaction analogous to the dioxygen reduction. Experimental data are presented for dioxygen reduction in acidic and basic media to illustrate application of the theory.     

Atrazine-selective polymers prepared by molecular imprinting of trialkylmelamines as dummy template species of atrazine

Synthetic polymer receptors selective for atrazine have been prepared by molecular imprinting using trialkylmelamines as template molecules in place of atrazine. Trialkylmelamines were shown to be useful as templates for introducing affinity for atrazine into ethylene glycol dimethacrylate-methacrylic acid copolymers. The polymers showed the selective binding capacity for triazine herbicides including atrazine, whereas agrochemicals in other categories were not adsorbed to the imprinted polymers. The group selectivity demonstrated was comparable with that of the original atrazine imprinted polymers. Use of the nonagrochemical template molecules as a substitution to atrazine has made it possible to synthesize herbicide-receptor polymers free from troubles caused by analyte contaminants, which are desired for analytical applications.     

An enzyme flow immunoassay that uses beta-galactosidase as the label and a cellobiose dehydrogenase biosensor as the label detector

The aim was to develop a fast generic enzyme flow immunoassay (EFIA) using a beta-galactosidase (beta-GAL) label in combination with colorimetric detection as well as with a new amperometric biosensor as the label detector. The amperometric biosensor was previously developed within the group for the determination of diphenols in surface water samples. Antigen (Ag, analyte), tracer (Ag*, antigen labeled with beta-GAL), and antibody (Ab) were incubated off-line. After the equilibrium was reached, the sample was introduced into the flow system. The antibody complexes, AgAb and Ag*Ab, were trapped in a protein G column while the free unbound tracer was eluted and detected by an amperometric biosensor downstream after substrate reaction. The enzyme label beta-GAL converted the substrate 4-aminophenyl-beta-D-galactopyranoside (4-APG) into 4-aminophenol (4-AP), which subsequently was detected by a cellobiose dehydrogenase (CDH) modified solid graphite electrode. 4-AP was first oxidized at the electrode surface at +300 mV vs Ag/AgCl, and the formed 4-imino quinone (4-IQ) was reduced back to 4-AP by the CDH in the presence of cellobiose. By combining the EFIA with the CDH biosensor, the overall signal of one tracer molecule is amplified at two occasions, i.e., one enzyme label converts the substrate into many 4-AP molecules, and second these are further amplified by the CDH biosensor. The optimum conditions for the EFIA in terms of the molar ratio between tracer and beta-GAL, temperature, flow rate, etc., was investigated with colorimetric detection, using 2-nitrophenyl-beta-D-galactopyranoside (2-NPG) as the beta-GAL substrate. The performance of both the colorimetric and CDH biosensor detection was investigated and both methods were applied for determination of the model compound atrazine in spiked surface water samples. Detection limits of 0.056 +/- 0.008 and 0.038 +/- 0.007 microg L(-1) and IC50 values of 2.04 +/- 0.294 and 0.42 +/- 0.08 microg L(-1) were obtained for colorimetric and CDH detection, respectively. Matrix effects were less pronounced with the CDH biosensor than with colorimetric detection.     

Bead-based electrochemical immunoassay for bacteriophage MS2

Viruses are one of four classes of biothreat agents, and bacteriophage MS2 has been used as a simulant for biothreat viruses, such as smallpox. A paramagnetic bead-based electrochemical immunoassay has been developed for detecting bacteriophage MS2. The immunoassay sandwich was made by attaching a biotinylated rabbit anti-MS2 IgG to a streptavidin-coated bead, capturing the virus, and then attaching a rabbit anti-MS2 IgG-beta-galactosidase conjugate to another site on the virus. beta-Galactosidase converts p-aminophenyl galactopyranoside (PAPG) to p-aminophenol (PAP). PAPG is electroinactive at the potential at which PAP is oxidized to p-quinone imine (PQI), so the current resulting from the oxidation of PAP to PQI is directly proportional to the concentration of antigen in the sample. The immunoassay was detected with rotating disk electrode (RDE) amperometry and an interdigitated array (IDA) electrode. With an applied potential of +290 mV vs Ag/AgCl and a rotation rate of 3000 rpm, the detection limit was 200 ng/mL MS2 or 3.2 x 10(10) viral particles/mL with RDE amperometry. A trench IDA electrode was incorporated into a poly(dimethyl siloxane) channel, within which beads were collected, incubated with PAPG, and PAP generation was detected. The two working electrodes were held at +290 and -300 mV vs Ag/AgCl, and electrochemical recycling of the PAP/PQI couple by the IDA electrode lowered the limit of detection to 90 ng/mL MS2, or 1.5 x 10(10) MS2 particles/mL.     

Oxidation of the pesticide atrazine at DSA electrodes

This paper presents the study of the electrochemical oxidation of the pesticide atrazine at a Ti/Ru(0.3)Ti(0.7)O(2) dimensionally stable anodes (DSA). The effect of using different supporting electrolytes (NaCl, NaOH, NaNO(3), NaClO(4), H(2)SO(4) and Na(2)SO(4)) during the galvanostatic electrolysis of atrazine was investigated. It was observed that the removal of atrazine and total organic carbon (TOC) was only achieved at appreciable rates when NaCl was used as the supporting electrolyte, due to the oxidising species formed in this electrolyte (e.g. ClO(-)). Variation of the NaCl concentration demonstrated that, although only low concentrations of NaCl are necessary to result in the complete removal of atrazine in solution, TOC removal is almost linearly dependent on the quantity of NaCl in solution. Examination of the applied current density indicates that the efficiency of TOC removal reaches a maximum at 60 mA cm(-2). Testing of alternative electrode materials containing SnO(2) did not improve the efficiency of atrazine removal in Na(2)SO(4), but in NaCl a small increase was observed. Overall there appears to be no great advantage in using SnO(2)-containing electrodes over the Ti/Ru(0.3)Ti(0.7)O(2) electrode.     

Preparation and in vitro characteristics of lactoferrin-loaded chitosan microparticles

In order to achieve the delivery and controlled release of lactoferrin (LF), a biologically multifunctional protein, chitosan microparticles loaded with LF were prepared. Several types of chitosan microparticles containing LF were prepared by the w/o emulsification-solvent evaporation method, and the particle characteristics and release properties in JP 2nd fluid, pH 6.8, were examined. All kinds of microparticles were obtained at a yield of more than 75% (w/w). LF-loaded microparticles prepared by nonsonication and nonaddition of sulfate, named Ch-LF(N), showed high drug content, small particle size and spherical particle shape. Also, for release properties, Ch-LF(N) exhibited gradual drug release over 7 hr with less remaining in the microparticles. Considering the mucoadhesive properties of chitosan microparticles, Ch-LF(N) are suggested to be useful for gradual supply to topical diseased sites or for effective delivery to intestinal areas with abundant LF receptors.     

Label-free sequence-specific DNA sensing using copper-enhanced anodic stripping of purine bases at boron-doped diamond electrodes

Stripping voltammetric determination of purine bases in the presence of copper ions at mercury, amalgam, or carbon-based electrodes has recently been utilized in analysis of DNA or synthetic oligodeoxynucleotides (ODNs). Here we report on copper-enhanced label-free anodic stripping detection of guanine and adenine bases in acid-hydrolyzed DNA at anodically oxidized boron-doped diamond electrode (AO-BDDE). The AO-BDDE was successfully applied in a three-electrode microcell in which an approximately 50 microL drop of the analyte solution can be efficiently stirred during the accumulation step by streaming of an inert gas. Accelerated mass transport due to the solution motion in the presence of copper resulted in enhancement of the guanine oxidation signal by about 2 orders of magnitude (compared to accumulation of the analyte from still solution not containing copper), allowing an easy detection of approximately 25 fmol of the ODNs. The proposed technique is shown to be suitable for a determination of purine (particularly guanine) content in DNA samples. Applications of the technique in magnetic bead-based DNA assays (such as hybridization with DNA sequences exhibiting asymmetrical distribution of purine/pyrimidine nucleotides between the complementary strands or monitoring of amplification of specific DNA fragments in a duplex polymerase chain reaction) are demonstrated.     

Detection of approximately 10(3) copies of DNA by an electrochemical enzyme-amplified sandwich assay with ambient O(2) as the substrate

The electrochemical sandwich-type, enzyme-amplified assay of Zhang, Kim, and Heller (Anal. Chem. 2003, 75, 3267-3269) was simplified by replacing the amplifying horseradish peroxidase with bilirubin oxidase (BOD). BOD catalyzes the reduction of ambient O(2) to water and obviates the need for adding H(2)O(2). Femtomolar (10(-)(15) M) concentrations of DNA were detected at a 10-microm-diameter tip of a carbon fiber electrode. Correspondingly, a few thousand copies of DNA were detected in approximately 5-microL samples. The sandwich is formed in an electron-conducting redox hydrogel, to the polymer of which a DNA capture sequence is bound. Capture of the analyte DNA and its hybridization with a BOD-labeled complementary DNA sequence, electrically connects the BOD label to the electron-conducting redox polymer, which is in electrical contact with the electrode. Placing the BOD in contact with the redox polymer thus converts the noncatalytic base layer into a catalyst for the electroreduction of O(2) to water at +0.12 V (vs Ag/AgCl) (Figure 1). In an exemplary assay, approximately 3000 copies of the iron transporting sequence of the sit gene of Shigella flexneri were detected without PCR amplification.     

Preparation and In Vitro Characteristics of Lactoferrin-loaded Chitosan Microparticles

ABSTRACT

In order to achieve the delivery and controlled release of lactoferrin (LF), a biologically multifunctional protein, chitosan microparticles loaded with LF were prepared. Several types of chitosan microparticles containing LF were prepared by the w/o emulsification-solvent evaporation method, and the particle characteristics and release properties in JP 2nd fluid, pH 6.8, were examined. All kinds of microparticles were obtained at a yield of more than 75% (w/w). LF-loaded microparticles prepared by nonsonication and nonaddition of sulfate, named Ch-LF(N), showed high drug content, small particle size and spherical particle shape. Also, for release properties, Ch-LF(N) exhibited gradual drug release over 7 hr with less remaining in the microparticles. Considering the mucoadhesive properties of chitosan microparticles, Ch-LF(N) are suggested to be useful for gradual supply to topical diseased sites or for effective delivery to intestinal areas with abundant LF receptors.     

Flow fractionation of microparticles under a dielectrophoretic field in a quadrupole electrode capillary.

A technique of fractionation for microparticles was proposed that utilized a unique combination of a dielectrophoretic (DEP) field generated by a quadrupole electrode and a laminar flow in a capillary of 82.5 microm in radius. The fabricated capillary possessed four platinum wires in its inside wall as a quadrupole electrode. In a nonuniform electric field generated by the quadrupole electrode, microparticles, such as polystyrene and carbon, in water experienced DEP forces in the radial direction. When a sample solution was pumped in, an ideal laminar flow perpendicular to the DEP force was formed inside the capillary. The microparticles dynamically migrated by the DEP force across the laminar flow while they were carried by the flow. A theoretical model taking the DEP force and the laminar flow pattern into account predicted the elution profiles of the single microparticles quantitatively. The elution times of the microparticles depended on the dielectric properties and the sizes of the microparticles, as well as the voltage and frequency of the applied alternating current.     

Another approach toward over 100,000-fold sensitivity increase in capillary electrophoresis: electrokinetic supercharging with optimized sample injection

Electrokinetic supercharging (EKS) is a powerful and practical method for multifold in-line concentration of various analytes prior to capillary electrophoresis (CE) analysis. However, a problem of insufficient sensitivity has always existed when trace analyte quantification by EKS-CE is a target, especially when coupled with conventional detectors. Normally this requires a greatly increased amount of analyte injected without separation degradation. In this contribution, we have shown that it is possible to substantially improve analyte loading and hence CE method detectability by modifying sample introduction configuration. The volume of sample vial was increased (from typical 500 μL to 17 mL), the common wire electrode was replaced by a ring electrode, and the sample solution was stirred. With these alterations, more analyte ions are accumulated within the effective electric field during electrokinetic injection and then maintained as focused zones due to transient isotachophoresis. The versatility of the customized EKS-CE approach for sample concentration was demonstrated for a mixture of seven rare-earth metal ions with an enrichment factor of 500?000 giving detection limits at or below 1 ng/L. These detection limits are over 100?000 times better than can be achieved by normal hydrodynamic injection, 1000 times better than the sensitivity thresholds of inductively coupled plasma atomic emission spectrometry (ICP-AES), and even close to those of inductively coupled plasma mass spectrometry (ICPMS).     

Reduction of the nonspecific binding of a target antibody and of its enzyme-labeled detection probe enabling electrochemical immunoassay of an antibody through the 7 pg/ml-100 ng/mL (40 fM-400 pM) range

We describe a simple, potentially low-cost, amperometric, enzyme-amplified, sandwich-type immunoassay, monitoring IgG at a concentration as low as approximately 7 pg/mL with a dynamic range of 10(4). The assay utilizes a screen-printed carbon electrode on which a redox hydrogel and avidin are co-electrodeposited. To neutralize nonspecifically binding positively charged microdomains of the avidin, two polyanions, poly(acrylic acid-co-maleic acid) and poly(acrylic acid), are applied. These polyanions bind to the film not only electrostatically but also by Michael addition reaction to cysteine, lysine, or arginine functions of the avidin. The electrode is then made specific for the analyte, for which rabbit IgG was chosen, by conjugating the film-bound avidin to biotin-labeled anti-rabbit IgG. After exposure to the tested solution and capture of rabbit IgG, the sandwich is completed by conjugation of horseradish-peroxidase (HRP)-labeled anti-rabbit IgG. Electrical contact between the HRP and the electrode-bound hydrogel results in the formation of an electrocatalyst for the electroreduction of H2O2 to water. The application of the poly(acrylic acid-co-maleic acid) and the poly(acrylic acid) reduces the nonspecific adsorption-associated noise, lowers the detection limit from 3 ng/mL (approximately 20 pM analyte antibody concentration) to approximately 7 pg/mL (approximately 40 fM analyte antibody concentration), and also expands the dynamic range to 10(4).     

Controlling analyte electrochemistry in an electrospray ion source with a three-electrode emitter cell

The inherent electrochemistry occurring at the emitter electrode of an electrospray ion source was effectively controlled by incorporating a three-electrode controlled-potential electrochemical cell into the controlled-current electrospray emitter circuit. Two different basic cell designs were investigated to accomplish this control, namely, a planar flow-by working electrode and a porous flow-through working electrode design, each operated with a potentiostat floated at the electrospray high voltage. Control of the analyte electrochemistry was tested using the indole alkaloid reserpine, which is often used to test the specifications of electrospray mass spectrometry instrumentation. Reserpine was relatively easy to oxidize (E(p) = 0.73 V vs Ag/AgCl) in the acidic electrospray medium (acetonitrile/water 1:1 v/v, 5.0 mM ammonium acetate, 0.75 vol % acetic acid) and was oxidized when the conventional electrospray emitter was used at low solution flow rate. With the proper cell auxiliary electrode configuration and adjustment of the working electrode potential, it was found that reserpine oxidation could be "turned off" at flow rates as low as 2.5 microL/min as well as at flow rates as high as 30-40 microL/min. Just as important, it was also possible to "turn on" essentially 100% oxidation of reserpine in this flow rate range. The area of the auxiliary electrode along with flow rate, which affect mass transport of analytes to this electrode, were found to be critical in controlling the electrochemical reactions in the emitter cell. Such control over analyte electrochemical reactions in the emitter has been difficult or impossible to achieve with a conventional electrospray emitter. This control is paramount in obtaining experimental results free from electrochemically generated artifacts of the analyte or in exploiting electrochemical reactions involving the analyte to analytical advantage.     

High performance metal oxide based sensing device using an electrode with a solid/liquid/air triphase interface

The wetting properties of an electrode surface are of significant importance to the performance of electrochemical devices because electron transfer occurs at the electrode/electrolyte interface. Described in this paper is a low-cost metal oxide electrocatalyst (CuO)-based high-performance sensing device using an enzyme electrode with a solid/liquid/air triphase interface in which the oxygen level is constant and sufficiently high. We apply the sensing device to detect glucose, a model test analyte, and demonstrate a linear dynamic range up to 50 mM, which is about 25 times higher than that obtained using a traditional enzyme electrode with a solid/liquid diphase interface. Moreover, we show that sensing devices based on a triphase assaying interface are insensitive to the significant oxygen level fluctuation in the analyte solution.

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