Chemical analysis of single cells and exocytosis

Recent advances in the development of microscale analytical techniques have allowed minute amounts of compounds of biological interest to be monitored in microenvironments. Microcolumn separation techniques, such as microcolumn liquid chromatography and capillary electrophoresis, provide a means of obtaining high-efficiency separations of analytes in picoliter to femtoliter volume samples. Voltammetric microelectrode techniques, such as amperometry and fast-scan cyclic voltammetry, are ideally suited for monitoring transiently occurring chemical events in cellular and subcellular processes owing to their rapid response times and small structural dimensions. The principles and applications of these techniques in single-cell analysis are discussed throughout this review. Multicomponent separations and quantitations of large invertebrate neurons of the land snail Helix neurons and the pond snail Planorbis corneus dopamine neurons, and of small mammalian cells, bovine adrenal cells, rat PC12 cells, and human lymphocytes, by use of microcolumn liquid chromatography and capillary electrophoresis are presented. Electrochemical monitoring of neurotransmitter exocytosis from single adrenal cells, from PC12 cells, and from the cell body of the Planorbis dopamine neuron is highlighted. Results obtained from both separation and voltammetric techniques in single-cell analyses will provide a better understanding of cellular and/or neuronal chemistry and biology in complicated living environments.