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P C Pandey

Publications and source records attributed to P C Pandey.

14 recordsLinked to original sources
PubMed2001

An organically modified silicate-based ethanol biosensor.

A novel electrocatalytic ethanol biosensor using ferrocene-encapsulated palladium (Pd)-linked organically modified sol-gel glass (ormosil) is reported. The alkoxy precursors used to prepare the new ormosil-based electrocatalytic biosensor are Pd-linked glycidoxypropyltrimethoxysilane and trimethoxysilane. Pd-glycidoxypropyltrimethoxysilane (black solution) is made by mixing aqueous solutions of palladium chloride and glycidoxypropyltrimethoxysilane. The new ormosil is made using a Pd-linked silane precursor, trimethoxysilane, an aqueous solution of ferrocene monocarboxylic acid, and HCl. Alcohol dehydrogenase (ADH) is assembled over the ferrocene-ormosil layer using polyvinyl alcohol and then protecting the immobilized enzyme layer using Millipore filter membranes (pore size 1 microm). The electrocatalytic response of immobilized ADH, soluble nicotinamide adenine dinucleotide, and Pd-linked ormosil-encapsulated ferrocene is then observed. The electrocatalytic oxidation of NADH and the subsequent ADH-catalyzed formation of NADH are monitored electrochemically. Typical results recorded after the addition of varying concentrations of ethanol are reported; however, the sensor is sensitive to other alcohol and known ADH-sensitive substrates. The stability and reproducibility of the new ethanol biosensor are reported.

Alcohol Dehydrogenase↗
PubMed1998

Ethanol biosensors and electrochemical oxidation of NADH.

Comparative studies of the electrochemical oxidation of reduced nicotinamide coenzyme (NADH) at the surfaces of chemically modified graphite paste electrodes (CMEs) are reported. Three different electroactive materials, tetracyanoquinodimethane (TCNQ), tetrathiafulvalene (TTF), and dimethyl ferrocene (dmFc), were used to construct three different chemically modified paste electrodes. The oxidation of NADH was examined on the basis of cyclic voltammetric measurements. The results show that all three mediators (TCNQ, TTF, and dmFc) behave as efficient mediators of the oxidation of NADH. The typical response curves of NADH at the CMEs surfaces are reported. Incorporating alcohol dehydrogenase and electroactive materials (TCNQ, TTF, and dmFc) within the graphite paste electrodes has led to the development of ethanol biosensors. Typical response curves for the ethanol analysis are reported. Comparative studies on the mediated electrochemical responses of the biosensors to ethanol are discussed.

Biosensing Techniques↗
PubMed1997

Peroxide biosensors and mediated electrochemical regeneration of redox enzymes.

This article describes the research investigations on the development of the amperometric biosensors based on mediated bioelectrochemistry. The mediated bioelectrochemistry involving horseradish peroxidase and glucose oxidase within the graphite paste is reported. The enzyme horseradish peroxidase together with electrochemical mediator was incorporated within the graphite paste electrode. The amperometric response is based on the mediated electrochemical regeneration of peroxidase within the paste. The mediated electrochemical regeneration of peroxidase and glucose oxidase was studied and compared using three different electron transfer mediators-tetracyanoquinodimethane (TCNQ), tetrathiafulvalene (TTF), and dimethyl ferrocene (dmFc). The mediated electrochemistry involving these three mediators was studied based on the cyclic voltammetry. The electrochemical measurements show that TTF is better mediator for the development of peroxide biosensor compared to TCNQ and dmFc. On the other hand, TCNQ is better mediator for the development of glucose sensor. The response curves for peroxide have been reported using these three mediators. A comparative study on the amperometric response based on the mediated electrochemical oxidation of peroxidase and glucose oxidase has also been made using these three mediators. The various parameters, i.e., background current, stability of the mediator within the graphite paste during the electrochemical measurements, and reproducibility of the amperometric response, are discussed.

Biosensing Techniques↗
PubMed1995

Peroxidase- and tetracyanoquinodimethane-modified graphite paste electrode for the measurement of glucose/lactate/glutamate using enzyme-packed bed reactor.

A flow injection analysis sensor for the measurement of glucose/lactate/glutamate is reported. The glucose oxidase/glutamate oxidase/lactate oxidase was immobilized on silanized controlled pore glass particles and packed into a Teflon column (i.d., 1.2 mm; length, 40 mm) to give a bed for glucose/lactate/glutamate. The hydrogen peroxide formed by the enzymatic reaction in the packed bed was monitored by a horseradish peroxidase- and tetracyanoquinodimethane (TCNQ)- modified graphite paste electrode at 50 mV vs Ag/AgCl. The glucose oxidase/lactate oxidase/glutamate oxidase were regenerated in the packed bed, whereas peroxidase was regenerated in the TCNQ-mediated graphite paste electrode by the oxidation of TCNQ. The oxidized TCNQ was electrochemically reduced at 50 mV vs Ag/AgCl. The cathodic current obtained by the reduction of TCNQ determined the concentration of the injected analytes in the packed bed. The system showed very rapid response. Response curves for the analysis of peroxide, glucose, lactate, and glutamate are reported.

Biosensing Techniques↗
PubMed1995

Evanescent fluorobiosensor for the detection of polyaromatic hydrocarbon based on DNA intercalation.

A flow-injection analysis (FIA) system coupled with an evanescent wave (EW) biosensor employing total internal reflection of fluorescence radiation (TIRF) for the detection of polyaromatic hydrocarbon that intercalates into DNA is reported. A highly fluorescent intercalator, "ethidium bromide," has been used as the reference compound for detection. The EW biosensor was developed according to the procedure described earlier (1,2). Data on the analysis of Naphthalene, 3-methylcholanthrene, 7,12-dimethylbenz(a)anthracene, 1,2-benzanthracene, and some standard reference materials supplied by the National Institute of Standards and Technology are reported. The relative ability of the polyaromatic hydrocarbon to displace ethidium bromide, based on the relative binding ratio, is found to be on the order of 7,12-dimethylbenz[a]anthracene > 3-methylcholanthrene > 1,2-benzanthracene > napthalene.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1995

Tetracyanoquinodimethane mediated glucose sensor based on a self-assembling alkanethiol/phospholipid bilayer.

An amperometric tetracyanoquinodimethane (TCNQ) mediated biosensor for glucose is described, based on a self-assembling alkanethiol/phospholipid bilayer laid down onto a gold surface. Gold was sputter deposited onto chromium coated silicon wafers to a thickness of 200 nm. A monolayer of alkanethiol was allowed to self-assemble from an ethanolic solution of dodecanethiol onto a freshly cleaned gold electrode in an overnight incubation. The monolayer was characterized by ellipsometric, impedance and cyclic voltammetry measurements (capacitance = 1.60 +/- 0.06 microF/cm2, and thickness 1.34 +/- 0.15 nm). A mixture of phospholipid liposomes containing free amino groups was placed on the monolayer and allowed to incubate overnight. The self-assembly of a phospholipid monolayer and allowed to incubate overnight. The onto the alkanethiol monolayer, resulted in the formation of a bilayer. The formation of bilayer was again characterized by impedance and cyclic voltammetry measurements (capacitance = 0.98 +/- 0.09 microF/cm2, and thickness = 1.85 +/- 0.22 nm). TCNQ has been incorporated into the liposomes before the formation of the bilayer. Glucose oxidase was cross-linked with the amino-groups of the phospholipids using bis [2-(sulphosuccinimiidooxicarbonyloxy) ethyl] sulphone. TCNQ which was incorporated in the bilayer acted as an efficient mediator to regenerate glucose oxidase. Cyclic voltammetry of the modified electrode and a response curve for the glucose sensor are reported.

Biosensing Techniques↗
PubMed1994

Application of photochemical reaction in electrochemical detection of DNA intercalation.

A flow injection analysis (FIA) system for the detection of the compounds that intercalate within DNA is reported. A derivative of 9,10-anthraquinone has been used as the reference compound for photoelectrochemical detection. The sodium salts of 9,10-anthraquinone-2,6-disulfonic acid and 9,10-anthraquinone-2-sulfonic acid are photochemically activated and then reduced in the presence of an electron donor (glucose). The electrochemical signal is based on the measurement of the anodic current resulting from the oxidation of the reduced form of 9,10-anthraquinone. The reduced form of the 9,10-anthraquinone is oxidized through a mediated mechanism at the surface of a tetracyanoquinodimethane-(TCNQ)-modified graphite paste electrode covered by a Nucleopore membrane. TCNQ acts as an efficient mediator for the oxidation of reduced 9,10-anthraquinone. Cyclic voltammetry, photocyclic voltammetry, and the photoelectrochemical FIA response of 9,10-anthraquinone are reported. Experimental results show that these anthraquinones can be intercalated within the helix of double-stranded calf thymus DNA. The anthraquinone molecules that are intercalated within DNA cannot be oxidized due to their limited transport to the modified electrode surface. This results in a decrease in the anodic current at a constant concentration of anthraquinone after intercalation. There is a linear relation between the decrease in electrochemical response and the DNA concentration at a constant concentration of anthraquinone. The intercalated anthraquinone molecules can be completely replaced by another intercalating agent (i.e., ethidium bromide) that is more strongly intercalated within DNA, thereby regenerating the electrochemical response.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Tetracyanoquinodimethane-mediated flow injection analysis electrochemical sensor for NADH coupled with dehydrogenase enzymes.

A flow injection analysis (FIA) sensor for the oxidation of NADH is reported. The system utilizes a graphite paste electrode modified with the electroactive material tetracyanoquinodimethane (TCNQ). TCNQ acts as an efficient mediator for the oxidation of NADH to biologically active NAD+. Alcohol dehydrogenase/lactate dehydrogenase and NAD+ were coimmobilized in TCNQ-modified graphite paste using polyethylenimine to develop a FIA sensor for ethanol/lactate. The system responded rapidly with wide linearity. Response curves for ethanol/lactate and NADH are reported.

Alcohol Dehydrogenase↗
PubMed1993

An amperometric flow-injection analysis biosensor for glucose based on graphite paste modified with tetracyanoquinodimethane.

A biosensor system using flow injection analysis (FIA) has been developed for the analysis of glucose in human serum. The system consists of the enzyme glucose oxidase incorporated into graphite paste modified with the electroactive material tetracyanoquinodimethane (TCNQ). TCNQ acts as an efficient mediator for oxidation of the reduced enzyme at 200 mV vs Ag/AgCl. The flow injection assay described has detection limits of 2 mM glucose using a 100-microliters sample injection through a 250-microliters sample loop. Data are presented to show the effect of sample injection volume and flow rate on the response of the FIA sensor. The biosensor exhibited excellent reproducibility for 800 injections. The loss of response after 800 injections was due to leaching of TCNQ from the graphite paste. Each assay takes 3 min giving a sample throughput of 20 per hour at a flow rate of 30 ml/h. The sensor was applied to the determination of glucose in human serum. The glucose measurements are in good agreement with those of a commercially available spectrophotometric method. Data showing the effect of interfering substances, ascorbic acid and acetaminophen, on the response of the sensor are also reported.

Acetaminophen↗
PubMed1992

Amperometric enzyme sensor for glucose based on graphite paste-modified electrodes.

Amperometric enzyme electrode for glucose is described based on the incorporation of glucose oxidase (GOD) into graphite paste modified with tetracyanoquinodimethane (TCNQ). The incorporated enzyme exhibits high activity and long-term stability over the earlier TCNQ-based glucose sensor (1). The sensor provides a linear response to glucose over a wide concentration range. The response time of the sensor is 15-50 sec, and the detection limit is 0.5 mM. Stable response to the substrate was obtained during a period of 35 d. Application of the sensor in the plasma analysis is reported.

Biosensing Techniques↗
PubMed1992

A new membrane electrode for the detection of antibody.

A new membrane electrode sensitive to specific antibody is described which incorporates dinitrophenyl antigen in polyvinyl chloride matrix membrane on to the surface of a solid-state graphite-loaded epoxy-resin electrode. The sensitivity of the electrode is based on the ionophoric property of the dinitrophenyl antigen. Response curves for the potassium ion and its specific antibody are reported.

Antibodies↗
PubMed1990

Studies on acetylcholine sensor and its analytical application based on the inhibition of cholinesterase.

Acetylcholine esterase electrodes, based on glass, Pd/PdO and Ir/IrO2 electrodes as pH sensor, using the immobilized acetylcholine esterase in acrylamide-methacrylamide hydrazides prepolymer are reported and compared. New data on the analysis of nicotine, fluoride ion, and some organophosphorus compounds are reported using the present AChE sensor based on the inhibition of the immobilized acetylcholine esterase. Reactivation of immobilized AChE after inhibition with reversible inhibitor, i.e. nicotine and fluoride ion is carried out using a mixture of working buffer and acetylcholine, whereas reactivation after inhibition with irreversible inhibitor, i.e. organophosphorus compounds is carried out using a mixture of acetylcholine and pyridine-2-aldoxime methiodide (PAM). The detection limits for the nicotine and fluoride ion are found to be 10(-5) M whereas for paraoxon, methyl parathion and malathion are found to be 10(-9) M and 10(-10) M.

Acetylcholine↗
PubMed1986

Disruptive effects of auditory signal delay on speech perception with lipreading.

The effect of auditory signal delay on audio-visual perception of videotaped sentence lists by Ss with normal hearing was measured. The test material consisted of sentences read by a man, with or without a picture representing as context one of the key words in each sentence. In Exper. I, 12 Ss (6M, 6F), inexperienced with lipreading, were presented test material in the audio-only (A), visual-only (V) and audio-visual (AV) modes. Speech signals were presented at 0 or -10 db S/N re a multitalker babble fixed at 60 dbA. The audio signal was delayed (re visual signal) in 6 steps from 0-300 msec. Exper. II repeated Exper. I with 6 Ss (2M, 4F) familiar with lipreading; the speech signal was presented at -5 db S/N and 4 audio delays from 0-240 msec. While these Ss performed better in the V mode than those in Exper. I, the main effects of context and delays were similar. The disruptive effect of the audio delay on speech perception with lipreading (AV mode) was a function of S/N, being relatively more disruptive at the worse S/N, but it was not significant for delays up to a range of 80-120 msec. The results are in agreement with the theory (McGrath and Summerfield, J. Acoust. Soc. Am., 1985, 77, 678-685) that sensitivity to audio-visual desynchrony is significant only at a syllabic level in connected speech. The results further imply that moderate delays of up to 80 msec introduced by speech-processing aids for lipreading, as for cochlear-implanted patients, will not interfere with the advantages of providing the auditory information.

Acoustic Stimulation↗