title: Evaluating the diffusion coefficient of dopamine at the cell surface during amperometric detection: disk vs ring microelectrodes.
abstract: During exocytosis, small quantities of neurotransmitters are released by the cell. These neurotransmitters can be detected quantitatively using electrochemical methods, principally with disk carbon fiber microelectrode amperometry. An exocytotic event then results in the recording of a current peak whose characteristic features are directly related to the mechanisms of exocytosis. We have compared two exocytotic peak populations obtained from PC12 cells with a disk carbon fiber microelectrode and with a pyrolyzed carbon ring microelectrode array, with a 500 nm ring thickness. The specific shape of the ring electrode allows for precise analysis of diffusion processes at the vicinity of the cell membrane. Peaks obtained with a ring microelectrode array show a distorted average shape, owing to increased diffusion pathways. This result has been used to evaluate the diffusion coefficient of dopamine at the surface of a cell, which is up to an order of magnitude smaller than that measured in free buffer. The lower rate of diffusion is discussed as resulting from interactions with the glycocalyx.
authors.affiliation: Department of Chemistry and Molecular Biology, University of Gothenburg, S-41296, Gothenburg, Sweden.
authors.forename: Raphaël
authors.initials: R
authors.lastname: Trouillon
authors.forename: Yuqing
authors.initials: Y
authors.lastname: Lin
authors.forename: Lisa J
authors.initials: LJ
authors.lastname: Mellander
authors.forename: Jacqueline D
authors.initials: JD
authors.lastname: Keighron
authors.forename: Andrew G
authors.initials: AG
authors.lastname: Ewing
mesh_terms: D000818:Animals; D002244:Carbon / Q000737:chemistry*; D000077482:Carbon Fiber; D002462:Cell Membrane / Q000737:chemistry* / Q000378:metabolism; D004058:Diffusion; D004298:Dopamine / Q000032:analysis* / Q000378:metabolism; D055664:Electrochemical Techniques / Q000295:instrumentation / Q000379:methods*; D008839:Microelectrodes; D016716:PC12 Cells; D011897:Random Allocation; D051381:Rats; D013499:Surface Properties
chemical_list: D000077482:Carbon Fiber; D002244:Carbon; D004298:Dopamine