Abstract | We report on steady-state UV-visible absorption, emission, and picosecond emission studies of milrinone
(MIR) drug in neutral water and complexed to cyclodextrins (R-, â-, ç-CD and dimethyl-â-CD (DM-â-CD)).
The results reveal that MIR forms a 1:1 inclusion complex with CD. Upon encapsulation the emission intensity
increases and the fluorescence lifetime changes from 65 ps to 240-350 ps, indicating a confinement effect
of the nanocages on the photophysical behavior of the drug. Due to its methyl groups, the DM-â-CD complex
shows the largest effect. The time-anisotropy experiments support the formation of 1:1 inclusion complexes
and indicate motion of the drug inside the nanocavity. Furthermore, results of PM3 calculations combined
with spectral and dynamical data show that the drug is not fully embedded into the cavities, and the
conformation of the included complex explains the relatively short lifetimes and low emission quantum yields
of these entities. |