| Budget Amount *help |
¥3,500,000 (Direct Cost: ¥3,500,000)
Fiscal Year 2003: ¥1,100,000 (Direct Cost: ¥1,100,000)
Fiscal Year 2002: ¥2,400,000 (Direct Cost: ¥2,400,000)
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| Research Abstract |
Enzyme switch is a novel biosensing device based on the conductometric measurements of polyaniline(PAn) film covered with enzymes. The enzyme switch might have following advantages over conventional enzyme sensors : 1)Sensing chip itself has a memory function, 2)response might be independent from the electrode size, 3)Miniaturization and integration are easy because of its simple structure. 4)Easy connection with actuators, since the resistance change is index. In this study, these advantages were verified by using prepared enzyme switches.
PAn loses its electroconductivity by oxidation and recovers it by reduction. If the oxidase-peroxidase(HRP) co-immobilized electrodes are prepared with PAn, when the produced compounds I and II are reduced at the surface of PAn,PAn might be oxidized and may lose its conductivity. By monitoring conductivity of PAn, "enzyme-switch", which gives "off" signal by the existence of specific substrate, might be constructed.
PAn film was prepared electrochemically over the two micro-patterned thin film electrodes under the acidic conditions. Then glucose oxidase(or lactate oxidase) and HRP were immobilized onto the PAn film by glutaraldehyde crosslinking method. By the addition of substrates, the decrease of PAn conductivity due to the enzyme reaction could be observed. The oxidized PAn recovered its conductivity by applying 0.1 V vs.Ag/AgCl. In flow system, it took approximately 3 min for switching from "on" to "off", or "off" to "on", and peak heights were correspond to substrate concentration. The prepared enzyme switch had advantages both as enzyme test strips and enzyme sensors. Voltage application was not necessary during the enzyme reaction, and the response could be preserved for at least 1h.
An integrated multi-channel enzyme switch for glucose and lactate was constructed onto the multi-channel electrodes. The integrated enzyme switch showed responses to glucose or lactate independently and the chemical cross-talk was not observed.
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