title: Enzyme-based choline and L-glutamate biosensor electrodes on silicon microprobe arrays.
abstract: Brain-implantable microprobe arrays, 6.5 mm shaft-length, incorporating several recessed Pt microelectrodes (50 μm×150 μm) and an integrated Ag/AgCl reference electrode fabricated by silicon micromachining dry etching techniques (DRIE) are described. The microelectrodes are coated by an enzyme membrane and a semi-permeable m-phenylenediamine layer for the selective detection of the neurotransmitters choline and L-glutamate at physiologically relevant concentrations. The functionalisation is based on electrochemically aided adsorption (EAA) combined with chemical co-cross-linking using glutaraldehyde and electrochemical polymerisation, respectively. These deposition methods are fully compatible with the fabricated microprobe arrays for the simultaneous detection of several analytes in different brain target areas. They are spatially controlled and allow fabricating biosensors on several microelectrodes in parallel or providing a cross-talk-free coating of closely spaced microelectrodes with different enzyme membranes. A sensitivity of 132±20 μA mM(-1) cm(-2) for choline and 95±20 μA mM(-1) cm(-2) for L-glutamate with limits of detections below 0.5 μM was obtained. The results of in vitro and in vivo experiments confirm the functional viability of the choline and l-glutamate biosensors.
authors: Ecole Polytechnique Fédérale de Lausanne (EPFL), Institute of Microengineering (IMT), Sensors, Actuators and Microsystems Laboratory (SAMLAB), Rue Jaquet-Droz 1, 2000 Neuchâtel, Switzerland. olivier.frey@epfl.ch
authors: O
authors: O
authors: Frey
authors: T
authors: T
authors: Holtzman
authors: R M
authors: RM
authors: McNamara
authors: D E H
authors: DE
authors: Theobald
authors: P D
authors: PD
authors: van der Wal
authors: N F
authors: NF
authors: de Rooij
authors: J W
authors: JW
authors: Dalley
authors: M
authors: M
authors: Koudelka-Hep
mesh_terms: D000818:Animals; D015374:Biosensing Techniques / Q000295:instrumentation; D001921:Brain / Q000378:metabolism*; D002794:Choline / Q000032:analysis*; D003217:Conductometry / Q000295:instrumentation*; D004867:Equipment Design; D019544:Equipment Failure Analysis; D018698:Glutamic Acid / Q000032:analysis*; D008297:Male; D008839:Microelectrodes; D018377:Neurotransmitter Agents / Q000032:analysis*; D051381:Rats; D012825:Silicon / Q000737:chemistry*
chemical_list: D018377:Neurotransmitter Agents; D018698:Glutamic Acid; D002794:Choline; D012825:Silicon