Abstract
An integrated NAD +-dependent enzyme field-effect transistor (ENFET) device for the biosensing of lactate is described. The aminosiloxane-functionalized gate interface is modified with pyrroloquinoline quinone (PQQ) that acts as a catalyst for the oxidation of NADH. A synthetic amino-derivative of NAD + is covalently linked to the PQQ monolayer. Faradaic impedance spectroscopy and chronopotentiometry are used as electrochemical methods for probing in situ bioaffinity interaction between NAD +-dependent enzyme, lactate dehydrogenase (LDH) (E.C. 1.1.1.27), and the NAD +-functionalized Au-electrode surface. The association constant of 1.5×10 5 M −1 was found by both techniques. The affinity complex formed between the NAD +/PQQ-assembly and the LDH is cross-linked and yields an integrated biosensor ENFET-device for the analysis of lactate. The device reveals the lower detection limit of 1×10 −4 M for lactate and the sensitivity of 24±2 mV dec −1. The response time of the device is as low as 15 s.
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