Implementation of a High-Repetition-Rate Laser in an AP-SMALDI MSI System for Enhanced Measurement Performance.

Matrix-assisted laser desorption/ionization mass spectrometry imaging is a promising tool in the life sciences for obtaining spatial and chemical information from complex biological samples. State-of-the-art setups combine high mass resolution and high mass accuracy with high lateral resolution, offering untargeted insights into biochemical processes on the single-cell length scale. Despite recent technological breakthroughs, the sensitivity and acquisition speed of many setups are often in competition with achievable pixel resolutions below 25 μm. New measurement modes were developed by implementing a high-repetition-rate laser into an AP-SMALDI10 ion source, coupled to an orbital trapping mass spectrometer. These new MSI modes allow for a modular use of the new setup. We demonstrate that the system allows single cell features to be visualized in mouse brain tissue sections at a pixel resolution of 5 μm and an imaging speed of 18 pixels/s. Furthermore, the analytical sensitivity was improved in another measurement mode by applying multiple pulses of a highly focused laser beam over larger square pixels ≥25 μm edge length, increasing ion signal intensities up to 20-fold on tissue and decreasing the limit of detection by 1 order of magnitude.