Surface-transfer mass spectrometry imaging on a monoisotopic silver nanoparticle enhanced target

A new method for both high-resolution laser desorption/ionization mass spectrometry and mass spectrometry imaging is described. The method could be considered as matrix-less because no additional matrix is needed for MS measurements and also because of surface-assisted laser desorption/ionization due to the nanoparticle-rich surface. The standard matrix-assisted laser desorption/ionization target containing unique monoisotopic cationic (109)Ag nanoparticles ((109)AgNPs) was used for high-resolution mass spectrometry imaging of fingermarks and also plant flower and plant stem cross sections with high mass accuracy. The methodology presented in this work allowed visualization of two drugs--anti-inflammatory ibuprofen and anticancer 5-fluorouracil--along with many other compounds found on the finger. Moreover, visualization of herbicide localization inside of the plant stem is also shown. The simple inorganic ions ionized by silver nanoparticles were also found and may be used for their localization in biological material. In addition, the methodology presented here does not require freezing of species or slice-making equipment.