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Integrated Electrochemical Analysis System with Microfluidic and Sensing Functions

View Article: PubMed Central - PubMed

ABSTRACT

An integrated device that carries out the timely transport of solutions and conducts electroanalysis was constructed. The transport of solutions was based on capillary action in overall hydrophilic flow channels and control by valves that operate on the basis of electrowetting. Electrochemical sensors including glucose, lactate, glutamic oxaloacetic transaminase (GOT), glutamic pyruvic transaminase (GPT), pH, ammonia, urea, and creatinine were integrated. An air gap structure was used for the ammonia, urea, and creatinine sensors to realize a rapid response. To enhance the transport of ammonia that existed or was produced by the enzymatic reactions, the pH of the solution was elevated by mixing it with a NaOH solution using a valve based on electrowetting. The sensors for GOT and GPT used a freeze-dried substrate matrix to realize rapid mixing. The sample solution was transported to required sensing sites at desired times. The integrated sensors showed distinct responses when a sample solution reached the respective sensing sites. Linear relationships were observed between the output signals and the concentration or the logarithm of the concentration of the analytes. An interferent, L-ascorbic acid, could be eliminated electrochemically in the sample injection port.

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Elimination of L-ascorbic acid. (a) Used electrodes. (b) Time course of the current generated on the working electrode. W. E., working electrode; R. E., reference electrode; A. E., auxiliary electrode.
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f11-sensors-08-01111: Elimination of L-ascorbic acid. (a) Used electrodes. (b) Time course of the current generated on the working electrode. W. E., working electrode; R. E., reference electrode; A. E., auxiliary electrode.

Mentions: In previous analyses, the sample injection port was used only as a reservoir to deliver a solution to the respective sensing sites. However, the port can also be used for preprocessing or to connect other modules for specific purposes. Here, we tested whether L-ascorbic acid could be eliminated in the sample injection port before the solution was delivered. L-Ascorbic acid is a representative interferent to amperometric sensors, and it is found in physiological fluids. To this end, the platinum electrode in the sample injection port, the Ag/AgCl electrode next to the sample injection port, and one of the gold valve electrodes were used as the working, reference, and auxiliary electrode, respectively [Figure 11 (a)]. The platinum electrode used for the elimination of L-ascorbic acid was the same shape and size as the sample injection port (diameter, 1.8 mm). A solution containing 0.1 mM L-ascorbic acid was dissolved in a 0.1 M phosphate buffer solution (pH 7.4) containing 0.1 M KCl and injected into the sample injection port, and +0.8 V was applied to the working electrode for a predetermined time. Then, the solution was transported to the glucose sensing site, and +0.7 V was applied to the working electrode for the sensor; subsequently, the generated current was measured. In this experiment, the enzyme was not immobilized, and L-ascorbic acid was directly oxidized on the working electrode.


Integrated Electrochemical Analysis System with Microfluidic and Sensing Functions
Elimination of L-ascorbic acid. (a) Used electrodes. (b) Time course of the current generated on the working electrode. W. E., working electrode; R. E., reference electrode; A. E., auxiliary electrode.
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3927525&req=5

f11-sensors-08-01111: Elimination of L-ascorbic acid. (a) Used electrodes. (b) Time course of the current generated on the working electrode. W. E., working electrode; R. E., reference electrode; A. E., auxiliary electrode.
Mentions: In previous analyses, the sample injection port was used only as a reservoir to deliver a solution to the respective sensing sites. However, the port can also be used for preprocessing or to connect other modules for specific purposes. Here, we tested whether L-ascorbic acid could be eliminated in the sample injection port before the solution was delivered. L-Ascorbic acid is a representative interferent to amperometric sensors, and it is found in physiological fluids. To this end, the platinum electrode in the sample injection port, the Ag/AgCl electrode next to the sample injection port, and one of the gold valve electrodes were used as the working, reference, and auxiliary electrode, respectively [Figure 11 (a)]. The platinum electrode used for the elimination of L-ascorbic acid was the same shape and size as the sample injection port (diameter, 1.8 mm). A solution containing 0.1 mM L-ascorbic acid was dissolved in a 0.1 M phosphate buffer solution (pH 7.4) containing 0.1 M KCl and injected into the sample injection port, and +0.8 V was applied to the working electrode for a predetermined time. Then, the solution was transported to the glucose sensing site, and +0.7 V was applied to the working electrode for the sensor; subsequently, the generated current was measured. In this experiment, the enzyme was not immobilized, and L-ascorbic acid was directly oxidized on the working electrode.

View Article: PubMed Central - PubMed

ABSTRACT

An integrated device that carries out the timely transport of solutions and conducts electroanalysis was constructed. The transport of solutions was based on capillary action in overall hydrophilic flow channels and control by valves that operate on the basis of electrowetting. Electrochemical sensors including glucose, lactate, glutamic oxaloacetic transaminase (GOT), glutamic pyruvic transaminase (GPT), pH, ammonia, urea, and creatinine were integrated. An air gap structure was used for the ammonia, urea, and creatinine sensors to realize a rapid response. To enhance the transport of ammonia that existed or was produced by the enzymatic reactions, the pH of the solution was elevated by mixing it with a NaOH solution using a valve based on electrowetting. The sensors for GOT and GPT used a freeze-dried substrate matrix to realize rapid mixing. The sample solution was transported to required sensing sites at desired times. The integrated sensors showed distinct responses when a sample solution reached the respective sensing sites. Linear relationships were observed between the output signals and the concentration or the logarithm of the concentration of the analytes. An interferent, L-ascorbic acid, could be eliminated electrochemically in the sample injection port.

No MeSH data available.