Influence of Drug Encapsulation within Mixed Micelles on the Excited State Dynamics and Accessibility to Ionic Quenchers

Photophysical techniques, specifically time-resolved fluorescence and laser flash photolysis, have proven to be noninvasive, straightforward, and valuable tools to demonstrate how drug encapsulation into biomimetic mixed micelles (MM) influences the dynamics of excited states and their accessibility to ionic quenchers. This concept has been illustrated by choosing a set of currently administered drugs containing a common naphthalene chromophore, namely, (S)-naproxen and its methyl ester, (R)-cinacalcet and (S)-propranolol. A remarkable increase of their triplet lifetimes is noticed when experiments are performed in MM, indicating efficient entrapment of the drugs in these supramolecular entities. Furthermore, a decrease of 1 order of magnitude in the quenching rate constant of the singlet and triplet excited states (by iodide or nitrite, respectively) is observed upon encapsulation into MM. This approach can in principle be extended to other microenvironments capable of incorporating photoactive compounds.