Chlorophyllide a/Cyclodextrin Interaction in Aqueous Solution

The interactions between Chlorophyllide a (Chlide), a pigment having the same structure of Chl a without the phytilic tail, and two CDs having the same moieties but different cavity size, the hydroxypropyl-β-cyclodextrin and the hydroxypropyl-γ-cyclodextrin, were studied in aqueous solutions by means of absorption, fluorescence spectroscopy, circular dichroism and isothermal titration calorimetry. The results obtained indicate that both cyclodextrins are able to modify the aggregation equilibrium of the pigment favouring the monomeric form

Cyclodextrin/chlorophyll a complexes as supramolecular photosensitizers

The interactions between chlorophyll a, and three cyclodextrins, hydroxypropyl-β-cyclodextrin heptakis(2,3,6-tri-O-methyl)-β-cyclodextrin and hydroxypropyl-γ-cyclodextrin, were studied in aqueous solutions by means of absorption, emission and circular dichroism spectroscopy. Nanosecond laser flash photolysis and steady-state singlet oxygen generation experiments were performed to clarify the photoactivity of chlorophyll a in these systems. Moreover the photosensitizing activity of these complexes towards human leukemia T-lymphocytes (Jurkat cells) was tested and compared with that of the free sensitizer, chlorophyll a. The results obtained indicate that each cyclodextrin is able to carry the pigment in monomeric form inside of cells producing singlet oxygen

Tetrakis(4-pyridyl)phorphyrin supramolecular complexes with cyclodextrins in aqueous solution

The formation of inclusion complexes of hydroxypropyl-bcyclodextrin, heptakis(2,6-di-O-methyl)-b-cyclodextrin and heptakis(2,3,6-tri-O-methyl)-b-cyclodextrin with 5,10,15,20- tetrakis(4-pyridyl)porphyrin (TpyP) has been studied in aqueous buffer solution (phosphate buffer pH 5 7 and I 5 0.01 M) to give a structural and spectroscopic characterization of a new class of potential sensitizers for photodynamic therapy. The interaction was investigated by a combination of UV/Vis absorption, fluorescence anisotropy, time-resolved fluorescence and circular dichroism. The experimental results point to the presence of the pigment in water in a monomeric complexed form. The fluorescence anisotropy measurements suggest that TpyP forms 1:1 complexes with heptakis(2,3,6-tri- O-methyl)-b-cyclodextrin and hydroxypropyl-b-cyclodextrin, while 1:2 complexes are obtained with heptakis(2,6-di-Omethyl)- b-cyclodextrin

“The effect of Cyclodextrines on the physicochemical properties of Chlorophyll a in aqueous solution”

The interactions between chlorophyll a and two â-cyclodextrins, that have the same cavity size but different substituents, were studied in aqueous solutions. These supramolecular host-guest complexes were examined by a combination of UV/vis absorption, circular dichroism, NMR, and steady-state and time-resolved fluorescence measurements. The results indicate that all cyclodextrins solubilize the pigment mainly in monomeric form in water. The pigment forms 1:1 complexes with the heptakis(2,3,6-tri-O-methyl)-â- cyclodextrin and 1:2 complexes with the hydroxypropyl-â-cyclodextrin. In such complexes the methyl groups of the cyclodextrin inner cavity are involved in the interaction with the pigment as evidenced by NMR measurements. We also measured the luminescence of singlet oxygen photosensitized by chlorophyll a in the inclusion complexes