We report the development of a new type of ambient mass spectrometry named laser desorption ionization droplet delivery mass spectrometry (LDIDD-MS). It utilizes a pulsed laser for desorption of molecules from cells or tissue substrates. The desorbed ions are picked up and delivered with directed sprayed liquid droplets on the laser-irradiated region to a mass spectrometer. By translating the desorption region on an XY moving stage, two-dimensional images of the desorbed/ionized ions are recorded.  As the region of desorption/ionization of LDIDD-MS is spatially limited to the laser beam spot size, the spatial resolution can be reduced to several microns. The timing of the laser pulse allows also exquisite temporal resolution.  For example, we obtained spatial resolution as low as 2.4 �m in microcontacted standard samples and ~3 �m for a pancreas tissue sample. We employed LDIDD-MS imaging for single cell analysis and observed a significant heterogeneity in the cellular apoptosis of HEK cells. LDIDD-MS also enables real-time measurement/imaging of exocytosed biomolecules from live cells. Images of exocytosis of neuropeptides and enzymes in PC12 upon biochemical or biophysical stimulation have also been acquired.

Ambient ionization mass spectrometric imaging with high spatiotemporal resolution

248th National Meeting (2014)

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