A Stable Zn(II) Metal–Organic Framework as Turn-On and Blue-Shift Fluorescence Sensor for Amino Acids and Dipicolinic Acid in Living Cells or Using Aerosol Jet Printing

Amino acids and dipicolinic acid (DPA) are important biomarkers for identifying human health. Establishing rapid, accurate, sensitive, and simple assays is essential for disease prevention and early diagnosis. In this work, a novel Zn(II) metal-organic framework (MOF) with the formula {[Zn₅(μ₃-OH)₂(BTDI)₂(dpp)₂]·dpp·4H₂O·2DMF}_n (<b>JXUST-53</b>, where <b>JXUST</b> denotes Jiangxi University of Science and Technology, H₄BTDI = 5,5'-(benzo[<i>c</i>][1,2,5]thiadiazole-4,7-diyl)diisophthalic acid; dpp = 1,3-di(4-pyridyl)propane) was successfully synthesized via a mixed-ligands strategy. <b>JXUST-53</b> exhibits a three-dimensional (4,10)-connected <i>deh1</i> topological structure, which remains stable after soaking in aqueous solutions with different pH values (1-12) and organic solvents for at least 24 h, showing high chemical and pH stability. As a potential fluorescence sensor, <b>JXUST-53</b> can specifically recognize l-threonine (l-Thr), l-histidine (l-His), and DPA in EtOH solutions through fluorescence enhancement and a blue-shift effect. It is worth noting that <b>JXUST-53</b> is the first MOF-based fluorescence sensor capable of recognizing l-Thr. In addition, the university logo of <b>JXUST</b> with <b>JXUST-53</b> deposited on it was printed by aerosol jet printing technology, enabling a portable and convenient method for monitoring DPA. More importantly, <b>JXUST-53</b> has good biocompatibility and low cytotoxicity to sense l-Thr, l-His, and DPA in living cells.