Complexation induced fluorescence and acid-base properties of dapoxyl dye with γ-cyclodextrin: a drug-binding application using displacement assays

Host-guest complexation of dapoxyl sodium sulphonate (DSS), an intramolecular charge transfer dye with water-soluble and non-toxic macrocycle gamma-cyclodextrin (gamma-CD), has been investigated in a wide pH range. Steady-state absorption, fluorescence and time-resolved fluorescence measurements confirm the positioning of DSS into the hydrophobic cavity of gamma-CD. A large fluorescence enhancement ca. 30 times, due to 1 : 2 complex formation and host-assisted guest-protonation have been utilised for developing a method for the utilisation of CD based drug-delivery applications. A simple fluorescence-displacement based approach is implemented at physiological pH for the assessment of binding strength of pharmaceutically useful small drug molecules (ibuprofen, paracetamol, methyl salicylate, salicylic acid, aspirin, and piroxicam) and six important antibiotic drugs (resazurin, thiamphenicol, chloramphenicol, ampicillin, kanamycin, and sorbic acid) with gamma-CD.