Binding behavior and in vitro cytotoxicity of inclusion complexes between aminopterin and cucurbit[7]uril

Aminopterin (AMT) is a kind of universal antineoplastic drugs, but it has severe toxic and side effects, leaving it rarely used in clinic. Herein, we found that cucurbit[7]uril (CB[7]) and AMT can form stable inclusion complexes, and the formation of CB[7]-AMT 2:1 supramolecular inclusion complex was confirmed by UV-visible absorption spectra, fluorescence spectra, ¹H NMR, and molecular modeling calculations in aqueous solution. Binding stability constants (Ks) were determined by UV-visible and fluorescence spectra method, with 3.88 × 10¹⁰ L² mol^–2 and 5.24 × 10¹⁰ L² mol^–2, respectively. The binding energy was calculated to be 102.6 kcal mol^–1 for the CB[7]-AMT complex. And then, through a series of cell experiments of CCK8 assay, DAPI staining and hoechst33342/PI double staining, we fully proved that the CB[7]-AMT complex can reduce the toxicity of AMT to normal cells such as hepatocyte line LO2, and improve its anticancer effect on cancer cells overexpressing spermine, typically like human colon cancer cell line HCT116. It confirmed that the CB[7]-AMT complex had the effect of reducing toxicity and increasing efficiency. These results indicated that CB[7]-AMT inclusion complex might be a promising novel formulation of AMT for its clinical development.