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Article

Scanning Electrochemical Microscopy of Model Neurons: Constant Distance Imaging

Ruwan T. Kurulugama,^†^‡ David O. Wipf,^§ Sara A. Takacs, Sirinun Pongmayteegul, Paul A. Garris, and John E. Baur*^†

Departments of Chemistry and Biological Sciences, Illinois State University, Normal, Illinois 61790, and Department of Chemistry, Mississippi State University, Mississippi State, Mississippi 39762

Anal. Chem., 2005, 77 (4), pp 1111–1117

DOI: 10.1021/ac048571n

Publication Date (Web): January 12, 2005

†

Department of Chemistry, Illinois State University.

‡

Current address: Department of Chemistry, Indiana University, Bloomington, IN 47405.

Department of Chemistry, Mississippi State University.

Department of Biological Sciences, Illinois State University.

Current address: Department of Neurology, Northwestern University Feinberg School of Medicine, Chicago, IL 60611.

Corresponding author. Fax: (309)438−5538. E-mail: jebaur@ilstu.edu.

Abstract

Undifferentiated and differentiated PC12 cells were imaged with the constant-distance mode of scanning electrochemical microscopy (SECM) using carbon ring and carbon fiber tips. Two types of feedback signals were used for distance control: the electrolysis current of a mediator (constant-current mode) and the impedance measured by the SECM tip (constant-impedance mode). The highest resolution was achieved using carbon ring electrodes with the constant-current mode. However, the constant-impedance mode has the important advantages that topography and faradaic current can be measured simultaneously, and because no mediator is required, the imaging can take place directly in the cell growth media. It was found that vesicular release events do not measurably alter the impedance, but the depolarizing solution, 105 mM K⁺, produces a dramatic impedance change such that constant-distance imaging cannot be performed during application of the stimulus. However, by operating the tip in the constant-height mode, cell morphology (via a change in impedance) and vesicular release could be detected simultaneously while moving the tip across the cell. This work represents a significant improvement over previous SECM imaging of model neurons, and it demonstrates that the combination of amperometry and constant-impedance SECM has the potential to be a powerful tool for investigating the spatial distribution of neurotransmitter release in vitro.

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