Conductive nanopipettes: a useful tool for localized detection and analysis of single nanoscale objects.

In this work open carbon nanopipettes (CNPs) with radius between 50 nm and 600 nm were used to control translocation of different size vesicles through the pipette orifice followed by nanoelectrochemical analysis. Vesicle impact electrochem-ical cytometry (VIEC) was used to determine the number of catecholamine molecules expelled from single vesicles onto an inner wall carbon surface where the duration of transmit-ters release was quantified and correlated to vesicle size all in the same nanotip. This in turn allows us to both size and count molecules for vesicles while in a living cell. Here, small and sharp open CNPs were employed to carry out intracellular vesicle impact electrochemical cytometry (IVIEC) with mini-mal invasion and high sensitivity. Our findings with VIEC reveal that vesicular content increases with vesicle size. Re-lease kinetics of vesicular transmitters and dense core size have the same relation with vesicle size, implying that vesicular dense core size determines speed of each release event. This direct correlation unravels one of the complexities of exocytosis.