Desorption/ionization mass spectrometry on array of silicon microtips
(a) Schematic view of MALDI TOF MS equipment (Bruker Saxonia), and (b) mass spectrogram of dopamine. Note the background signal generated by the matrix (4-hydroxy--cyanocinnamic acid).
(a) Principle of desorption/ionization of a biosample for the MALDI method (hydrophobic spot on the target plate), the DIOS method (porous silicon spot on a silicon wafer), and the DIOSD method (porous silicon dioxide spot on a silicon wafer) in comparison with (b) the DIOSTA method.
Cross-sectional view of the gated silicon tips.
Step-by-step fabrication process of the array of gated silicon tips.
Scanning electron microscopy pictures of silicon wafer: (a) after plasma etching of silicon to form tips; (b) after deposition of plasma-enhanced chemical-vapor deposition layer, Cr–Au bilayer and photoresist (AZ); and (c) after opening windows in photoresist layer.
(a) DIOSTA platform with three spots and (b) a few gated silicon tips not covered with the biosample.
Mass spectrogram of dopamine 65 pmol per spot: (a) DIOSTA method, spectrogram was obtained for 100 laser-light pulses and (b) DIOSD method, spectrogram was obtained for 165 laser-light pulses. Positive (protonized) molecular ion at a m/z of 154.1 and its fragment at 137.03, as well as signals at m/z’s of 176.0 and 192.0, which are sodium and potassium adducts of dopamine, may be seen.
Mass spectrogram of LGG tripetide 40 pmol per spot: (a) DIOSTA method, spectrogram was obtained for 15 laser-light pulses; (b) DIOS method; and (c) DIOSD method. Spectrograms (b) and (c) were obtained for 165 laser-light pulses. Positive (protonized) molecular ion at a m/z of 246.2 and signals at m/z’s of 268.2 and 284.2, which are sodium and potassium adducts of tripeptide, may be seen.
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