Indium Tin Oxide devices for amperometric detection of vesicular release by single cells

The microfabrication and successful testing of a series of three ITO (Indium Tin Oxide) microsystems for amperometric detection of cells exocytosis are reported. These microdevices have been optimized in order to simultaneously (i) enhance signal-to-noise ratios, as required electrochemical monitoring, by defining appropriate electrodes geometry and size, and (ii) provide surface conditions which allow cells to be cultured over during one or two days, through apposite deposition of a collagen film. The intrinsic electrochemical quality of the microdevices as well as the effect of different collagen treatments were assessed by investigating the voltammetric responses of two classical redox systems, Ru(NH(3))(6)(3+/2+) and Fe(CN)(6)(3-/4-). This established that a moderate collagen treatment does not incur any significant alteration of voltammetric responses or degradation of the excellent signal-to-noise ratio. Among these three microdevices, the most versatile one involved a configuration in which the ITO microelectrodes were delimited by a microchannel coiled into a spiral. Though providing extremely good electrochemical responses this specific design allowed proper seeding and culture of cells permitting either single cell or cell cluster stimulation and analysis.