title: Quantitative analysis of immobilized penicillinase using enzyme-modified AlGaN/GaN field-effect transistors.
abstract: Penicillinase-modified AlGaN/GaN field-effect transistors (PenFETs) are utilized to systematically investigate the covalently immobilized enzyme penicillinase under different experimental conditions. We demonstrate quantitative evaluation of covalently immobilized penicillinase layers on pH-sensitive field-effect transistors (FETs) using an analytical kinetic PenFET model. This kinetic model is explicitly suited for devices with thin enzyme layers that are not diffusion-limited, as it is the case for the PenFETs discussed here. By means of the kinetic model it was possible to extract the Michaelis constant of covalently immobilized penicillinase as well as relative transport coefficients of the different species associated with the enzymatic reaction which, exempli gratia, give information about the permeability of the enzymatic layer. Based on this analysis we quantify the reproducibility and the stability of the analyzed PenFETs over the course of 33 days as well as the influence of pH and buffer concentration on the properties of the enzymatic layer. Thereby the stability measurements reveal a Michalis constant KM of (67 ± 13)μM while the chronological development of the relative transport coefficients suggests a detachment of physisorbed penicillinase during the first two weeks since production. Our results show that AlGaN/GaN PenFETs prepared by covalent immobilization of a penicillinase enzyme layer present a powerful tool for quantitative analysis of enzyme functionality.
authors.affiliation: I. Physikalisches Institut, Justus-Liebig-Universität Gießen, Heinrich-Buff-Ring 16, 35392 Gießen, Germany. Electronic address: gesche.m.muentze@exp1.physik.uni-giessen.de.
authors.forename: Gesche Mareike
authors.initials: GM
authors.lastname: Müntze
authors.affiliation: Walter Schottky Institut, Technische Universität München, Am Coulombwall 3, 85748 Garching, Germany.
authors.forename: Barbara
authors.initials: B
authors.lastname: Baur
authors.affiliation: I. Physikalisches Institut, Justus-Liebig-Universität Gießen, Heinrich-Buff-Ring 16, 35392 Gießen, Germany.
authors.forename: Wladimir
authors.initials: W
authors.lastname: Schäfer
authors.affiliation: I. Physikalisches Institut, Justus-Liebig-Universität Gießen, Heinrich-Buff-Ring 16, 35392 Gießen, Germany.
authors.forename: Alexander
authors.initials: A
authors.lastname: Sasse
authors.affiliation: Walter Schottky Institut, Technische Universität München, Am Coulombwall 3, 85748 Garching, Germany.
authors.forename: John
authors.initials: J
authors.lastname: Howgate
authors.affiliation: I. Physikalisches Institut, Justus-Liebig-Universität Gießen, Heinrich-Buff-Ring 16, 35392 Gießen, Germany.
authors.forename: Kai
authors.initials: K
authors.lastname: Röth
authors.affiliation: I. Physikalisches Institut, Justus-Liebig-Universität Gießen, Heinrich-Buff-Ring 16, 35392 Gießen, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Eickhoff
mesh_terms: D017607:Aluminum Compounds / Q000737:chemistry*; D015374:Biosensing Techniques / Q000295:instrumentation*; D003198:Computer Simulation; D017076:Computer-Aided Design; D003217:Conductometry / Q000295:instrumentation*; D004566:Electrodes; D004800:Enzymes, Immobilized / Q000032:analysis / Q000737:chemistry; D004867:Equipment Design; D019544:Equipment Failure Analysis; D005708:Gallium / Q000737:chemistry*; D008956:Models, Chemical; D010405:Penicillinase / Q000032:analysis* / Q000737:chemistry*; D014173:Transistors, Electronic
chemical_list: D017607:Aluminum Compounds; D004800:Enzymes, Immobilized; C513700:aluminum gallium nitride; D005708:Gallium; D010405:Penicillinase
keywords: AlGaN/GaN HEMT; Bioelectronics; Biosensor; EnFET; Functionalization; Penicillinase