Graphene-Coated Glass Substrate for Continuous Wave Laser Desorption and Atmospheric Pressure Mass Spectrometric Imaging of Live Hippocampal Tissue.

Atmospheric pressure mass spectrometric (AP-MS) imaging technology combined with an inverted optical microscopic system is a powerful tool to obtain information about presence and spatial distributions of specific biomolecules of interest in live tissue. To get mass spectrometric (MS) information in an ambient environment, efficient desorption and ionization is essential. In this paper, we are demonstrating a new method for an efficient desorption process using a graphene-coated glass substrate and with a continuous wave (CW) laser for high resolution AP-MS imaging of live hippocampal tissue. We found that desorption of biomolecules in a live tissue slice was possible with the aid of a graphene-coated glass substrate and indirectly applying a 532 nm CW-laser on graphene substrate. Interestingly, the desorption efficiency of live tissue on the graphene-coated substrate was strongly dependent on the number of graphene layers. The single-layer graphene is found to be the most sensitive substrate for efficient desorption and reproducible high-resolution hippocampal tissue imaging applications. The subsequent ionization process with nonthermal plasma jets generates sufficient amounts of molecular ions to obtain high-resolution MS 2D images of the cornu ammonis (CA) and the dentate gyrus (DG) regions of the hippocampal tissue.