High-Resolution Live-Cell Imaging and Analysis by Laser Desorption/Ionization Droplet Delivery Mass Spectrometry.
We have developed 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 observed upregulation of phosphatidylcholine (PC) with a relatively shorter carbon chain length and downregulation of PC with a relatively longer carbon chain length. We also applied LDIDD-MS for a real-time direct measurements of live-cell exocytosis. The catecholamine dopamine and trace amines (phenethylamine and tyramine) were detected from live PC12 cells without damaging them.
Department of Chemistry, Stanford University , Stanford, California 94305 United States.
Jae Kyoo
JK
Lee
Department of Chemistry, Stanford University , Stanford, California 94305 United States.|Department of Chemistry - BMC, Uppsala University , SE-75124 Uppsala, Sweden.
Erik T
ET
Jansson
Center for Plant Aging Research, Institute for Basic Science (IBS) , Daegu 42988, Republic of Korea.|Department of New Biology, DGIST , Daegu 42988, Republic of Korea.
Hong Gil
HG
Nam
Department of Chemistry, Stanford University , Stanford, California 94305 United States.
Richard N
RN
Zare
D000596:Amino Acids / Q000032:analysis*; D000818:Animals; D017209:Apoptosis / Q000502:physiology; D001921:Brain / Q000378:metabolism / Q000473:pathology*; D004298:Dopamine / Q000032:analysis; D005089:Exocytosis; D005260:Female; D057809:HEK293 Cells; D006801:Humans; D066292:Lipid Droplets / Q000737:chemistry*; D051379:Mice; D008810:Mice, Inbred C57BL; D016716:PC12 Cells; D010713:Phosphatidylcholines / Q000032:analysis; D051381:Rats; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
D000596:Amino Acids; D010713:Phosphatidylcholines; D004298:Dopamine