On-tissue pyrene-1-boronic acid labeling assisted MALDI imaging of catecholamines in porcine adrenal gland.

• Commercially available pyrene-1-boronic acid was effective to label catecholamines. • On-tissue labeling strategy was developed to label catecholamines in-situ. • The strategy succeeded in imaging catecholamines in adrenal gland tissue sections. • The strategy proved to be robust, easy-to-use and low-cost. • Distributions of catecholamines obtained by MALDI-MSI matched well optical images. In this study, an on-tissue chemical labeling - matrix assisted laser desorption/ionization-mass spectrometry imaging (MALDI-MSI) method was developed for visualization of the distribution of three catecholamine (CA) compounds (dopamine, epinephrine and norepinephrine) in porcine adrenal gland. Commercially available pyrene-1-boronic acid (PBA) was employed as an effective in situ derivatizing reagent dissolved in acetonitrile containing 0.1% pyridine for the chemical labeling and the matrix coating. Without extra matrix coating, the tissue section was directly analyzed by MALDI-MS. The detection specificity and sensitivity were greatly improved with the on-tissue PBA labeling and successful imaging of the three CAs in porcine adrenal gland was achieved. Compared with previously reported methods for MALDI-MSI of the CAs, the analytical strategy proposed in the study provided a robust, easy-to-use and low-cost on-tissue chemical derivatization method that facilitated simultaneous molecular imaging of the three compounds. [ABSTRACT FROM AUTHOR]