Potentiometric sensing of butyrylcholinesterase based on in situ generation and detection of substrates

ACS Appl. Mater. Interfaces

Wang

Qin

2013

Self Cite

Pulsed galvanostatic control of ion fluxes across polymeric membrane ion-selective electrodes (ISEs) is an emerging field for potentiometric sensing. Herein we report a novel potentiometric enzyme immunoassay based on currentcontrolled release of an enzyme substrate, which eliminates the addition of marker ions in the sample solution. In this method, the carboxylated poly(vinyl chloride) matrix at the outer layer of the ISE membrane is employed to attach a primary antibody. A sandwich immunoassay with an alkaline phosphatase labeled antibody (ALP-Ab) as the reporter is used for the determination of human IgG (as a model protein). The large difference between the lipophilicity of the substrate ion and that of the product ion allows p-nitrophenyl phosphate to be used as the enzyme substrate for potentiometric immunosensors. After the immunoreactions, the captured ALP-Ab catalyzes the hydrolysis of the substrate ions released at the sample−membrane interface by using the pulsed galvanostatic technique. This process can be potentiometrically determined by measuring the open circuit potential of the ISE. Under optimal conditions, the potential response of the proposed immunosensor is proportional to the concentration of human IgG in the range of 50−1000 ng/mL with a detection limit of 30 ng/mL (3σ). Owing to simplicity and independence of sample volume and sample turbidity, the proposed potentiometric immunoassay offers a viable alternative to those based on optical absorbance.

Section: Introductionmentioning

confidence: 99%

Pulsed Galvanostatic Control of a Polymeric Membrane Ion-Selective Electrode for Potentiometric Immunoassays

ACS Appl. Mater. Interfaces

Wang

Qin

2013

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“…fluxes in the direction of the sample solution) has been developed for measuring a wide range of analytes which can decrease the concentrations of the indicator ions released at the samplemembrane phase boundary via complexing [17], redox [18] or enzyme-catalyzed reactions [19][20][21]. Such an ISE membrane not only serves as a polymer matrix for reagent release, but also works as a transducer for sensitive potentiometric detection, making the ISE membrane very attractive for sensor miniaturization.…”

Section: Introductionmentioning

confidence: 99%

Potentiometric flow injection system for determination of reductants using a polymeric membrane permanganate ion-selective electrode based on current-controlled reagent delivery

Song

Liang

et al. 2011

Analytica Chimica Acta

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a b s t r a c tA polymeric membrane permanganate-selective electrode has been developed as a current-controlled reagent release system for potentiometric detection of reductants in flow injection analysis. By applying an external current, diffusion of permanganate ions across the polymeric membrane can be controlled precisely. The permanganate ions released at the sample-membrane interface from the inner filling solution of the electrode are consumed by reaction with a reductant in the sample solution thus changing the measured membrane potential, by which the reductant can be sensed potentiometrically. Ascorbate, dopamine and norepinephrine have been employed as the model reductants. Under the optimized conditions, the potential peak heights are proportional to the reductant concentrations in the ranges of 1.0 × 10 −5 to 2.5 × 10 −7 M for ascorbate, of 1.0 × 10 −5 to 5.0 × 10 −7 M for dopamine, and of 1.0 × 10 −5 to 5.0 × 10 −7 M for norepinephrine, respectively with the corresponding detection limits of 7.8 × 10 −8 , 1.0 × 10 −7 and 1.0 × 10 −7 M. The proposed system has been successfully applied to the determination of reductants in pharmaceutical preparations and vegetables, and the results agree well with those of iodimetric analysis.

“…9 This system can be used as a simple and effective potentiometric biosensor based on disturbance of transmembrane diffusion fluxes of ion-selective electrodes under near-zero-current conditions. Such an ISE membrane not only serves as a polymer matrix for reagent release but also works as a transducer for sensitive potentiometric detection, making the ISE membrane very attractive for sensor miniaturization.…”

mentioning

confidence: 99%

“…In addition to the conventional ingredients, 9 ETH 500 was incorporated into the ISE membrane. This lipophilic electrolyte was used to decrease the membrane resistance and thereby the IR voltage drop inside the currentpolarized membrane.…”

mentioning

confidence: 99%

Current-Driven Ion Fluxes of Polymeric Membrane Ion-Selective Electrode for Potentiometric Biosensing

Qin

2009

J. Am. Chem. Soc.

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We report here on a novel polymeric membrane ion-selective electrode (ISE) for potentiometric sensing of enzymes and their inhibitors. Diffusion of the substrate ions across the ISE membrane can be controlled precisely by applying an external current. The substrate ions released at the membane-sample interface are consumed by reaction of the enzyme in solution or immobilized on the surface of the membrane, which can be sensed potentiometrically. Applications of this approach include the detection of both free and labeled enzymes in biosensors and enzyme immunoassays and the measurement of bioanalytes involved in enzymatic systems.Electrochemical control of ion transport through polymeric membranes is an emerging field of research that offers the possibility of programmable tuning of ion fluxes and lowering of the detection limits of potentiometric polymeric membrane ISEs. 1 Current-driven ion fluxes across ISE membranes have been extensively investigated and have been applied in solid-contact ISEs, 2 polyion sensors, 3 pulstrodes, 4 controlled-current coulometry, 5 chronopotentiometric flash titrations, 6 and backside-calibration potentiometry. 7 Although sensitive detection of peptidase activities and surface-confined proteins using chronopotentiometric polymeric membrane electrodes has been reported, 2,8 the use of ISEs with current-controlled release of reagents for sensitive detection and quantification of biomolecules has not been realized to date.Recently, we developed a promising detection system that makes use of outward ion fluxes through an ISE membrane (i.e., fluxes in the direction of the sample solution) to provide controlled-release substrates for in situ biosensing of enzymes and their inhibitors. 9 This system can be used as a simple and effective potentiometric biosensor based on disturbance of transmembrane diffusion fluxes of ion-selective electrodes under near-zero-current conditions. Such an ISE membrane not only serves as a polymer matrix for reagent release but also works as a transducer for sensitive potentiometric detection, making the ISE membrane very attractive for sensor miniaturization. However, once the substrate ions released at the sample-membrane interface are consumed by the enzyme, especially at high concentrations, the recovery time may be rather long. Reproducible results can only be obtained if a constant release of primary ions in the direction of the sample solution is available before each measurement. Herein, we introduce a novel potentiometric biosensing system using pulsed-current-driven reagent delivery, which addresses such limitations. It will be shown that the current-controlled release of substrate from the ISE enables sensing of enzyme activities and screening of different enzyme inhibitors in a rapid and reproducible way.