Plasmonic Polyurea-Functionalized Titanium Dioxide Nanotube Substrates for Whole-Plant Imprinting Mass Spectrometry Imaging

As per- and polyfluoroalkyl substances (PFASs) are persistent pollutants with high bioaccumulation potential, insights into their absorption, transport, and spatial distribution in whole plants are critical for evaluating their ecological impact and risks. Here, we develop a novel gold nanoparticle-coated urea-linked organic polymer-functionalized TiO 2 nanotube substrate for whole-plant imprinting mass spectrometry imaging (MSI) in negative-ion modes. We investigated the spatially and temporally distinctive absorption, translocation, and accumulation patterns of three PFASs with different carbon chain lengths (CCLs), including perfluorobutanesulfonate (PFBS, C4), perfluorohexanesulfonate (PFHxS, C6), and perfluorooctanesulfonate (PFOS, C8), in whole hydroponically grown cowpea plants. The MSI results reveal that PFBS with the shortest CCLs presents the highest mobility that is distributed throughout the entire plant within 6 h, whereas PFOS presents limited transport and accumulates primarily in the roots and stems, even after prolonged exposure. Cross-sectional MSI further reveals that both PFBS and PFHxS easily penetrate root tissues and accumulate in the vascular cylinder, whereas PFOS is likely restricted by the Casparian strip in the endodermis, rendering it hard to enter the phloem and xylem of roots. Collectively, this whole-plant imprinting MSI serves as a powerful tool for deciphering the CCL-dependent translocation mechanisms of PFASs in plants, contributing to understanding and pollution management of PFASs in an ecological environment.