Single-cell monitoring

A microelectrode alone is not enough it has to be used in connection with a fast scan and not only that, but sometimes with an electrocatalyst. This is the case for single-cell monitoring of insulin and a process called exocytosis in which a bunch of insulin molecules, about 360,000 of them, are deposited, eventually to reach the blood stream and to trigger mechanisms that will consume the glucose that has risen beyond a healthy limit. Remarkably, when one considers the cost to the nation of diabetes, all too little is known about it at this molecular level. To craft a cure, here, too, one must look to the microelectrode and its abilities to obtain sufficient knowledge of events at the level of the individual cell. 

S. p. Arbault, N. Sojic, D. Bmce, C. Amatore, A. Sarasin and M. Vuillaume, Oxidative stress in cancer prone xeroderma pigmentosum fibroblasts. Realtime and single cell monitoring of superoxide and nitric oxide production with microelectrodes. Carcinogenesis an information retrieval publication, 25(4), 509-515 (2004). 

FIGURE 7.5 7,8-BPQ increases intracellular Ca2+ in murine spleen cells (A) and in both B and T cells (B). Single cell suspensions were prepared from murine spleens. Splenocytes were loaded with Fluo-3/AM dye for one hour and then treated with 7,8-BPQ, 1,6-BPQ, 3,6-BPQ, or DMSO (control). Surface-marker-defined T cells and B cells were treated with 7,8-BPQ or DMSO. Following treatment, the immediate intracellular Ca2+ response was continuously monitored for 15 minutes. Results are shown as the change in Mean Channel Fluorescence SEM. The numbers shown in this figure were the averages of triplicate determinants. Adapted from Gao et al., 2005. 

A. J. Cunningham and J. B. Justice, Jr., Approaches to Voltammetric and Chromatographic Monitoring of Neurochemicals in Vivo, J. Chem. Ed. 1987, 64, A34. Another Nafion-coated electrode can detect 10 10 mol of the neurotransmitter nitric oxide within a single cell [T. Malinski and Z. Taha, Nitric Oxide Release from a Single Cell Measured in Situ by a Porphyrinic-Based Microsensor, Nature 1992, 358, 676]. 

Tamaki, E., Sato, K., Tokeshi, M., Sato, K., Aihara, M., Kitamori, T., Single-cell analysis by a scanning thermal lens microscope with a microchip direct monitoring of cytochrome c distribution during apoptosis process. Anal. Chem. 2002, 74, 1560-1564. 

MONITORING NEUROTRANSMITTERS IN THE INTACT BRAIN AND OTHER SINGLE-CELL STUDIES... 

The use of fast scan cyclic voltammetry has already been described (Section 8.6). In general, microelectrodes, in some cases modified by electrocatalysts, are making it possible to learn about biological events on the scale of a single cell. Among the more important achievements (Wightmann, 1996) is the monitoring of dopamine released after stimulation from neurons in the intact brain and involved in neurotransmission. 

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