Supramolecular interaction of methotrexate with cucurbit[7]uril and analytical application

The supramolecular interaction between cucurbit[7]uril (CB[7]) as the host and the anti-cancer drug methotrexate (MTX) as the guest was studied using fluorescence spectroscopy, UV-visible absorption spectroscopy, ¹H NMR, 2D NOESY, and theoretical calculations. The experimental results confirmed the formation of 1:2 inclusion complex with CB[7] and indicated a simple and sensitive competitive method for the fluorescence detection of MTX. It was found that the fluorescence intensities of CB[7]-palmatine, CB[7]-berberine and CB[7]-coptisine were quenched linearly upon the addition of MTX. The linear ranges obtained in the detection of MTX were 0.1-15μgmL^-1, 0.2-15μgmL^-1, and 0.4-15μgmL^-1 with detection limits of 0.03μgmL^-1, 0.06μgmL^-1, and 0.13μgmL^-1, respectively. This method can be used for the determination of MTX in biological fluids. These results suggested that cucurbit[7]uril is a promising drug carrier for targeted MTX delivery and monitoring, with improved efficacy and reduced toxicity in normal tissues.