Laser-Induced Graphene Microarrays for Enhanced Quantitative Precision in Surface-Assisted Laser Desorption/Ionization Mass Spectrometry

Abstract Laser desorption/ionization mass spectrometry offers distinct advantages for biomolecular analysis owing to its high salt tolerance, low sample consumption, and soft ionization capability. However, localized laser−sample interactions are inherently affected by heterogeneous distributions of analytes and materials, leading to substantial variation between measurements. Improving signal precision has therefore long been a central pursuit in mass spectrometric analysis for reliable qualitative and quantitative biomolecular information. Herein, we report a laser-induced graphene (LIG) microarray platform for enhancing analytical precision in surface-assisted laser desorption/ionization mass spectrometry (SALDI-MS). A straightforward thermal confinement strategy enabled high-resolution LIG patterning under CO2 laser irradiation. Using an unmodified commercial laser cutter, monolithic porous LIG domains with feature sizes as small as 60 μm, below the MS laser spot diameter, were directly patterned on polyimide films. The wettability contrast between hydrophilic LIG and hydrophobic polyimide guided analyte accumulation onto SALDI-active LIG spots, which were fully interrogated by the MS laser for reproducible desorption/ionization. This integrated control over LIG feature size and analyte localization reduced the relative standard deviation of MS signal intensity from 78.47% on the unconfined substrate to 6.27% across 30 microarray spots. The platform demonstrated applicability to diverse biomolecules in both positive and negative ion modes. Quantitative accuracy was further demonstrated through enzyme kinetic studies, giving kinetic parameters consistent with conventional colorimetric results. More importantly, LIG microarray-assisted SALDI-MS enables direct molecular tracking of colorless native substrate turnover, underscoring the broader potential of nanostructured carbon interfaces for reaction-resolved mass spectrometric analysis.