Alternating Electric Field‐Assisted Matrix Nano‐Coating for High Spatial Resolution MALDI Imaging

The simultaneous achievement of matrix nano‐coating and efficient in situ enrichment of analytes is currently an important aspect affecting the ability of matrix‐assisted laser desorption/ionization mass spectrometry imaging (MALDI‐MSI) to efficiently explore endogenous compounds in situ with high‐resolution. Herein, a novel matrix coating approach called alternating electric field‐assisted matrix nano‐coating (AEFAMnC) is reported, which is designed to amplify the capabilities of high‐resolution MALDI imaging. The use of AEFAMnC achieves matrix nano‐coating (the smallest crystal size, ca. 70 nm), resulting in superior uniform matrix deposition. Interestingly, AEFAMnC leverages asymmetric alternating electric fields to initiate a repetitive forced micro‐extraction process, which significantly enhance the in situ enrichment of compounds on the sample surface for more adequate co‐crystallization with the matrix. These features finally improve in situ ionization efficiency and high‐resolution imaging performance of endogenous compounds across various biological samples (i.e ., rat brain, germinating Chinese yew seeds, and single cells) at 5‐ µ m pixel size. Overall, for the first time, AEFAMnC simultaneously achieves both matrix nano‐coating and in situ repetitive forced micro‐extraction of analytes, significantly improving the performance of high‐spatial‐resolution MALDI‐MSI. AEFAMnC has far‐reaching implications in high‐resolution MALDI imaging, particularly in MS‐based single‐cell spatial omics studies.