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We have developed [1] a new ambient-ionization mass spectrometric technique named laser desorption/ionization droplet delivery mass spectrometry(LDIDD-MS).LDIDD-MS permits high-resolution,high-sensitivity imaging of tissue samples as well as measurements of both single-cell apoptosis and live-cell exocytosis.A pulsed(15 Hz)UV laser beam(266 nm)is focused on a surface covered with target analytes to trigger their desorption and ionization.A spray of liquid droplets is simultaneously directed onto the laser-focused surface region to capture the ionized analytes and deliver them to a mass spectrometer.The approach of rapid and effective capturing of molecules after laser desorption/ionization allows the limit of detection for the amino acid lysine to be as low as 2 amol under ambient ionization conditions.Two-dimensional maps of the desorbed/ionized species are recorded by moving the sample on an XY translational stage.The spatial resolution for imaging with LDIDD-MS was determined to be 2.4 μm for an ink-printed pattern and 3 μm for mouse brain tissue.We applied LDIDD-MS to single-cell analysis of apoptotic HEK cells.Differences were observed in the profiles of fatty acids and lipids between healthy HEK cells and those undergoing apoptosis.We also applied LDIDD-MS for a real-time direct measurements of live-cell exocytosis.We have also developed [2] a technique to monitor spatially confined surface reactions with mass spectrometry under ambient conditions,without the need for voltage or organic solvents so that this technique can be applied to cells.Fused-silica capillaries immersed in an aqueous solution,positioned in close proximity to each other and the functionalized surface,created a laminar flow junction with a resulting reaction volume of~5 pL.The setup was operated with a syringe pump,delivering reagents to the surface through a fused-silica capillary.The other fused-silica capillary was connected to a Venturi easy ambient sonic-spray ionization source,sampling the resulting analytes at a slightly higher flow rate compared to the feeding capillary.The combined effects of the inflow and outflow,maintains a chemical microenvironment,where the rate of advective transport overcomes diffusion.We are applying this new technique to make a chemical analysis of cell colonies.