A Cost-effective hybrid method for homogeneous matrix coating in matrix-assisted laser desorption/ionization mass spectrometry imaging using simultaneous spin and spray deposition

Abstract

A cost-effective, thin-film spin-coating method for homogeneousmatrix deposition in matrix-assisted laser desorption/ionizationmass spectrometry imaging (MALDI-MSI) is presented. In thismethod, the matrix solution is nebulized directly onto the samplesurface during continuous rotation in the spin coater, enablingsimultaneous spraying and centrifugal spreading for uniform filmformation. Although spin coating produces highly uniform matrixlayers, its widespread adoption in MALDI-MSI is hindered by thehigh cost of commercial instruments. To address this limitation,an in-house spin coater is developed and optimized. A fractionalfactorial design identified flow rate, matrix volume, and rotationspeed as the most critical parameters for achieving uniform depo-sition. Under optimal conditions (60 psi, 10 μL·min1, 400 μL, and10 cm at 35 a.u.), the system produces homogeneous matrix filmsacross entire glass slides. The effectiveness of this integratedspray during spin method is demonstrated by imaging the dis-tinct spatial distributions of key lipids and metabolites in mousebrain, strawberry, and carrot tissues. This work establishes the in-house spin coater as a feasible and robust tool for enhancingreproducibility and data quality in routine MALDI-MSI workflows.