Dendritic Molecular Baskets for Selective Binding of Toxic Methotrexate

We describe the preparation, assembly, recognition characteristics, and bioactivity of dendritic basket 612-. This novel cavitand has a deep aromatic pocket with three (S)-glutamic acid dendrons at the rim to amplify water solubility and prevent self-association. 1H NMR spectroscopy, calorimetry (ITC), and mass spectrometry (ESI-MS) measurements validate the formation of an inclusion complex between 612- and anticancer drug methotrexate (MTX2-) in water (Kd = 9.2 μM). To identify the docking pose, a comparison of computed (DFT and MM) and experimental 1H NMR chemical shifts suggests that MTX2- folds inside 612- (π···π), forming HBs with the peptidic dendrons while anchoring (C-H···π) to the aromatic pocket through its N-methyl group. In consequence, 612- selectively binds MTX2- in competition with structurally similar folic acid and leucovorin (reversal poisoning agent). While the host is biocompatible (HEK293; IC50 > 150 μM) and produces inclusion complex [MTX⊂6]14- in cell media, it experiences limitation in pharmacokinetic sequestration of MTX2- as dihydrofolate reductase's affinity to the drug is suggested to prevail over that of 612-. Nonetheless, considering the basket's biocompatibility, tunability, and chemoselectivity, it stands as the leading candidate in the pursuit of an effective abiotic antidote for methotrexate poisoning.