title: Amperometric detection of single vesicle acetylcholine release events from an artificial cell.
abstract: Acetylcholine is a highly abundant nonelectroactive neurotransmitter in the mammalian central nervous system. Neurochemical release occurs on the millisecond time scale, requiring a fast, sensitive sensor such as an enzymatic amperometric electrode. Typically, the enzyme used for enzymatic electrochemical sensors is applied in excess to maximize signal. Here, in addition to sensitivity, we have also sought to maximize temporal resolution, by designing a sensor that is sensitive enough to work at near monolayer enzyme coverage. Reducing the enzyme layer thickness increases sensor temporal resolution by decreasing the distance and reducing the diffusion time for the enzyme product to travel to the sensor surface for detection. In this instance, the sensor consists of electrodeposited gold nanoparticle modified carbon fiber microelectrodes (CFMEs). Enzymes often are sensitive to curvature upon surface adsorption; thus, it was important to deposit discrete nanoparticles to maintain enzyme activity while depositing as much gold as possible to maximize enzyme coverage. To further enhance sensitivity, the enzymes acetylcholinesterase (AChE) and choline oxidase (ChO) were immobilized onto the gold nanoparticles at the previously determined optimal ratio (1:10 AChE/ChO) for most efficient sequential enzymatic activity. This optimization approach has enabled the rapid detection to temporally resolve single vesicle acetylcholine release from an artificial cell. The sensor described is a significant advancement in that it allows for the recording of acetylcholine release on the order of the time scale for neurochemical release in secretory cells.
authors.affiliation: Department of Chemical and Biological Engineering, Chalmers University of Technology , 41296 Gothenburg, Sweden.
authors.forename: Jacqueline D
authors.initials: JD
authors.lastname: Keighron
authors.forename: Joakim
authors.initials: J
authors.lastname: Wigström
authors.forename: Michael E
authors.initials: ME
authors.lastname: Kurczy
authors.forename: Jenny
authors.initials: J
authors.lastname: Bergman
authors.forename: Yuanmo
authors.initials: Y
authors.lastname: Wang
authors.forename: Ann-Sofie
authors.initials: AS
authors.lastname: Cans
mesh_terms: D000109:Acetylcholine / Q000378:metabolism*; D000429:Alcohol Oxidoreductases; D000818:Animals; D058045:Artificial Cells / Q000166:cytology* / Q000378:metabolism; D015374:Biosensing Techniques; D002712:Chlorides / Q000378:metabolism; D022162:Cytoplasmic Vesicles / Q000378:metabolism*; D004298:Dopamine / Q000378:metabolism; D055664:Electrochemical Techniques; D006046:Gold; D017612:Gold Compounds / Q000378:metabolism; D053768:Metal Nanoparticles; D008839:Microelectrodes; D013997:Time Factors
chemical_list: D002712:Chlorides; D017612:Gold Compounds; D006046:Gold; C024568:gold tetrachloride, acid; D000429:Alcohol Oxidoreductases; C019888:choline oxidase; D000109:Acetylcholine; D004298:Dopamine
keywords: Biosensor; acetylcholine; amperometry; artificial cell; enzymes; exocytosis; gold nanoparticles