title: Enzyme assays using sensor arrays based on ion-selective carbon nanotube field-effect transistors.
abstract: In the fields of clinical diagnostics and point-of-care diagnosis as well as food and environmental monitoring there is a high demand for reliable high-throughput, rapid and highly sensitive assays for a simultaneous detection of several analytes in complex and low-volume samples. Sensor platforms based on solution-processable electrolyte-gated carbon nanotube field-effect transistors (CNT-FETs) are a simple and cost-effective alternative for conventional assays. In this work we demonstrate a selective as well as direct detection of the products of an enzyme-substrate interaction, here the for metabolic processes important urea-urease system, with sensors based on spray-coated CNT-FETs. The selective and direct detection is achieved by immobilizing the enzyme urease via certain surface functionalization techniques on the sensor surface and further modifying the active interfaces with polymeric ion-selective membranes as well as pH-sensitive layers. Thereby, we can avoid the generally applied approach for a field-effect based detection of enzyme reactions via detecting changes in the pH value due to an on-going enzymatic reaction and directly detect selectively the products of the enzymatic conversion. Thus, we can realize a buffering-capacity independent monitoring of changes in the substrate concentration.
authors.affiliation: Institute for Nanoelectronics, Department of Electrical Engineering and Information Technology, Technische Universität München, 80333 Munich, Germany. Electronic address: katharina.melzer@nano.ei.tum.de.
authors.forename: K
authors.initials: K
authors.lastname: Melzer
authors.affiliation: Institute for Nanoelectronics, Department of Electrical Engineering and Information Technology, Technische Universität München, 80333 Munich, Germany.
authors.forename: V Deep
authors.initials: VD
authors.lastname: Bhatt
authors.affiliation: Faculty of Chemistry, University of Warsaw, 02-093 Warsaw, Poland.
authors.forename: E
authors.initials: E
authors.lastname: Jaworska
authors.affiliation: Institute for Nanoelectronics, Department of Electrical Engineering and Information Technology, Technische Universität München, 80333 Munich, Germany.
authors.forename: R
authors.initials: R
authors.lastname: Mittermeier
authors.affiliation: Faculty of Chemistry, University of Warsaw, 02-093 Warsaw, Poland.
authors.forename: K
authors.initials: K
authors.lastname: Maksymiuk
authors.affiliation: Faculty of Chemistry, University of Warsaw, 02-093 Warsaw, Poland.
authors.forename: A
authors.initials: A
authors.lastname: Michalska
authors.affiliation: Institute for Nanoelectronics, Department of Electrical Engineering and Information Technology, Technische Universität München, 80333 Munich, Germany.
authors.forename: P
authors.initials: P
authors.lastname: Lugli
mesh_terms: D015374:Biosensing Techniques / Q000295:instrumentation*; D057075:Enzyme Assays / Q000295:instrumentation*; D004800:Enzymes, Immobilized / Q000737:chemistry / Q000378:metabolism*; D004867:Equipment Design; D006801:Humans; D037742:Nanotubes, Carbon / Q000737:chemistry*; D014173:Transistors, Electronic; D014508:Urea / Q000032:analysis / Q000378:metabolism*; D014510:Urease / Q000737:chemistry / Q000378:metabolism*
chemical_list: D004800:Enzymes, Immobilized; D037742:Nanotubes, Carbon; D014508:Urea; D014510:Urease
keywords: Array; Electrolyte-gated CNT-FET; Enzyme–substrate interactions; Ion-selective CNT-FET; Urea