title: Branched nanotrees with immobilized acetylcholine esterase for nanobiosensor applications.
abstract: A novel lab-on-a-chip nanotree enzyme reactor is demonstrated for the detection of acetylcholine. The reactors are intended for use in the RISFET (regional ion sensitive field effect transistor) nanosensor, and are constructed from gold-tipped branched nanorod structures grown on SiN(x)-covered wafers. Two different reactors are shown: one with simple, one-dimensional nanorods and one with branched nanorod structures (nanotrees). Significantly higher enzymatic activity is found for the nanotree reactors than for the nanorod reactors, most likely due to the increased gold surface area and thereby higher enzyme binding capacity. A theoretical calculation is included to show how the enzyme kinetics and hence the sensitivity can be influenced and increased by the control of electrical fields in relation to the active sites of enzymes in an electronic biosensor. The possible effects of electrical fields employed in the RISFET on the function of acetylcholine esterase is investigated using quantum chemical methods, which show that the small electric field strengths used are unlikely to affect enzyme kinetics. Acetylcholine esterase activity is determined using choline oxidase and peroxidase by measuring the amount of choline formed using the chemiluminescent luminol reaction.
authors.affiliation: Department of Pure and Applied Biochemistry, Center for Chemistry and Chemical Engineering, Lund University, PO Box 124, SE-22100 Lund, Sweden.
authors.forename: Klas
authors.initials: K
authors.lastname: Risveden
authors.forename: Kimberly A
authors.initials: KA
authors.lastname: Dick
authors.forename: Sunil
authors.initials: S
authors.lastname: Bhand
authors.forename: Patrik
authors.initials: P
authors.lastname: Rydberg
authors.forename: Lars
authors.initials: L
authors.lastname: Samuelson
authors.forename: Bengt
authors.initials: B
authors.lastname: Danielsson
mesh_terms: D000110:Acetylcholinesterase / Q000737:chemistry* / Q000378:metabolism; D015374:Biosensing Techniques / Q000295:instrumentation / Q000379:methods*; D002794:Choline / Q000737:chemistry; D004800:Enzymes, Immobilized / Q000737:chemistry* / Q000378:metabolism; D056656:Lab-On-A-Chip Devices; D008855:Microscopy, Electron, Scanning; D043942:Nanotubes / Q000737:chemistry / Q000648:ultrastructure
chemical_list: D004800:Enzymes, Immobilized; D000110:Acetylcholinesterase; D002794:Choline