An integrated NAD+-dependent enzyme-functionalized field-effect transistor (ENFET) system: Development of a lactate biosensor

Maya Zayats, Andrei B. Kharitonov, Eugenii Katz, Andreas F. Buückmann, Itamar Willner*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

62 Scopus citations

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. Synthetic amino-derivative of NAD+ is covalently linked to the PQQ monolayer. An affinity complex formed between the NAD+/PQQ-assembly and the NAD+-cofactor-dependent lactate dehydrogenase (LDH) is crosslinked and yields an integrated biosensor ENFET-device for the analysis of lactate. Biocatalyzed oxidation of lactate generates NADH that is oxidized by PQQ in the presence of Ca2+-ions. The reduced catalyst, PQQH2, is oxidized by O2 in a process that constantly regenerates PQQ at the gate interface. The biocatalyzed formation of NADH and the O2-stimulated regeneration of PQQ yield a steady-state pH gradient between the gate interface and the bulk solution. The changes in the pH of the solution near the gate interface and, consequently, the gate potential are controlled by the substrate (lactate) concentration in the solution. The device reveals the 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.

Original languageEnglish
Article number568
Pages (from-to)671-680
Number of pages10
JournalBiosensors and Bioelectronics
Volume15
Issue number11-12
DOIs
StatePublished - 2000

Keywords

  • Biosensor
  • ENFET
  • ISFET
  • Lactate
  • NAD-dependent enzyme
  • PQQ

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