Mapping Molecular Signatures in Plant Leaves, Flowers, and Fruits by a TiO2 Nanotube-Based Plasmonic Chip for Imprint Mass Spectrometry Imaging

Mapping molecular signatures within a fragile leaf or flower of medicinal plants with mass spectrometry imaging (MSI) techniques is crucial in plant biology yet remains a great challenge due to the inability to slice such samples. Herein, we constructed a composite substrate, hydrophobic polydopamine-modified TiO2 nanotube coated with plasmonic gold nanoparticle (AuNP-hPDA-TDNT) and exploited its potential as a surface-assisted laser desorption/ionization (SALDI) substrate for imprinting/stamping MSI analysis. With the integrated advantages of satisfactory imprinting/ stamping capability and enhanced ion production, this AuNP-hPDA-TDNT substrate-based SALDI-MSI exhibits remarkable performance in mapping tissue-specific distribution patterns of functional metabolites in medicinal plant (i.e., Cailiaranilitis roseus, Ginkgo biloba, and fairoplia iniegerrima) leaves/flowers and fruits (i.e., strawberry and cherry tomato) regardless of tedious sample preparation. Collectively, we believe that this functionalized TiO2 nanotube substrate will expand the scope of SALDI-MSI in plant science, providing more biologically relevant insights into the functions and mechanisms of plant systems.