Electrochemistry and Mass Spectrometry Imaging of Nanometer Neurotransmitter Vesicles

In recent years, micro-/nano-electrochemical approaches have been developed to realize the quantitative measurement of intravesicular content and real-time monitoring of their release dynamics. We originally developed flow vesicle impact electrochemical cytometry (FVIEC),1 and subsequently stochastic VIEC2 and intracellular VIEC (IVIEC)3 to provide a highly effective way to quantify the electroactive contents inside vesicles. This has allowed direct comparison of the quantity of molecules released by exocytosis to those in the vesicles. Partial release is observed across all cell types examined to date by the electrochemical methods and is regulated by drugs,4 aging, and repeated simulations.5 We have confirmed this with NanoSIMS imaging of dopamine lost and external drug captured by closing vesicles in stimulated PC12 cells.6 Moreover, we have used NanoSIMS to compare the fraction released as a funcion of nanometer vesicle size and show it is independent of vesicle size.7

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2.      J. Dunevall, H. Fathali, N. Najafinobar, J. Lovric, J. Wigström, A-S. Cans, and A. G. Ewing, J. Am. Chem. Soc., 137, 4344–4346 (2015).

3.      X. Li, S. Majdi, J. Dunevall, H. Fathali, and A. G. Ewing, Angew. Chem. Int. Ed., 54, 11978-11982 (2015).

4.      Y. Wang and A. G. Ewing, ChemBioChem, 22,807-813 (2021).

5.            C. Gu, A. Larsson and A. G. Ewing, Proc Natl Acad Sci USA, 116, 21409-21415 (2019).

6.      T. D. K. Nguyen, L. Mellander, A. Lork, A. Thomen, M. Philipsen, M.E. Kurczy, N. T. N. Phan and A. G. Ewing, ACS Nano, 16, 4831–4842 (2022).

7.      T. D. K. Nguyen, S. Rabasco, A. A. Lork, A. Du Toit, A. G. Ewing, Angew. Chem. Int. Ed., 2023, 62, e202304098, https://doi.org/10.1002/anie.202304098