title: Effect of cyclodextrin nanocavity confinement on the photorelaxation of the cardiotonic drug milrinone.
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 (alpha-, beta-, gamma-CD and dimethyl-beta-CD (DM-beta-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 approximately 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-beta-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.
authors.affiliation: Departamento de Química Física, Sección de Químicas, Facultad de Ciencias del Medio Ambiente, Universidad de Castilla-La Mancha, Avda. Carlos III, S.N., 45071 Toledo, Spain.
authors.forename: Maged
authors.initials: M
authors.lastname: El-Kemary
authors.forename: Juan Angel
authors.initials: JA
authors.lastname: Organero
authors.forename: Lucia
authors.initials: L
authors.lastname: Santos
authors.forename: Abderrazzak
authors.initials: A
authors.lastname: Douhal
mesh_terms: D002316:Cardiotonic Agents / Q000737:chemistry*; D003505:Cyclodextrins / Q000737:chemistry*; D020105:Milrinone / Q000737:chemistry*; D008958:Models, Molecular; D015394:Molecular Structure; D049329:Nanostructures / Q000737:chemistry*; D010777:Photochemistry; D012680:Sensitivity and Specificity; D013050:Spectrometry, Fluorescence / Q000379:methods; D013056:Spectrophotometry, Ultraviolet / Q000379:methods; D013997:Time Factors
chemical_list: D002316:Cardiotonic Agents; D003505:Cyclodextrins; D020105:Milrinone