Supramolecular interaction of a cancer cell photosensitizer in the nanocavity of cucurbit[7]uril: A spectroscopic and calorimetric study.

The interaction of small biologically active molecules in the nanocavity of supramolecular host is very interesting and thriving research area. In the presence of supramolecular host the absorption and emission properties of small biologically active molecules were modulated several folds compared to bulk solution. In this study we have investigated the supramolecular interaction of a cancer cell photosensitizer molecule harmane in the presence of cucurbit[7]uril (CB7) as host in aqueous buffer solution (pH∼7.2). We have used steady state absorption, emission and time resolved fluorescence spectroscopy techniques. The thermodynamics of the binding between harmane in the nanochannel of CB7 were studied by using isothermal titration calorimetry (ITC) method. The emission properties of harmane are modulated several fold in the presence of CB7. ITC study indicates that the complexation between harmane and CB7 are enthalpically favourable.