Interaction between chlorophyll a and b-cyclodextrin derivatives in aqueous solutions

Cyclodextrins (CDs) are widely used as delivery systems of poorly water soluble drugs in pharmacological applications. The delivery system produces an increase of aqueous solubility of the drug and significant modifications in its physico-chemical and pharmacological properties. In this paper we report the results of our study on aqueous solutions of chlorophyll a, a natural pigment useful as sensitizer in the photodynamic therapy, and two CDs: hydroxypropyl- b-cyclodextrin and heptakis(2,6-di-O-methyl)-b-cyclodextrin. The interactions between chlorophyll and CDs and the effect produced by the presence of the CDs on the aggregation of chlorophyll were studied by calorimetric and UV-Vis spectrophotometric measurements respectively.