Development of bimetallic nanoparticles for Surface-Assisted Laser Desorption/Ionisation Mass Spectrometry imaging of small molecules

Metallic nanoparticles (NPs) receive increasing attention as desorption/ionization substrate for Surface-Assisted Laser Desorption Ionization-MS (SALDI-MS) [1]. Metallic NPs offer high extinction coefficients of the ionization laser (in the UV-Visible range of wavelengths) and are able to ionize small molecules with little interferences in the low m/z range with a simple sample preparation [2]. SALDI-MSI is adapted to study the variations of the molecular composition associated with various diseases and to visualize the localization of pertinent small molecules in complex biological tissues. Innovative Au@Ag (core@shell) bimetallic NPs are interesting for SALDI applications, especially because controlling the thickness of the Ag shell around the Au core allows the tuning of the absorption in near-UV. The Au@Ag NPs permits to vary the energy transfer for an efficient ionization and desorption of analytes adsorbed to the NPs. Moreover Au@Ag NPs can also also be used for Surface-Enhanced Raman Spectroscopy (SERS) imaging. We report here a study of ovarian cancer tissue using Au@Ag NPs to localize the tumor by SERS imaging and to gain molecular insight of tumors by SALDI-MSI.