Identification of ROS produced by photodynamic activity of chlorophill/cyclodextrin inclusion complexes

Photodynamic therapy (PDT) is a way of treating malignanttumors and hyperproliferative diseases. It is based on the useof photosensitizer, herein the chlorophyll a (chl a), and alight of an appropriate wavelength. The interaction of thephotosensitizer (PS) with the light produces reactive oxygenspecies (ROS), reactive oxygen species, powerful oxidizingagents, which cause critical damage to the tissue. To solubilizechl a in aqueous solution and to obtain it as monomer,we have used cyclodextrins, carriers which are able to interactwith the pigment and form the inclusion complex. Theaim of this study is to examine which types of ROS areformed by Chl a/cyclodextrin complexes in phosphate bufferedsolution and cell culture medium, using specic molecules,called primary acceptors, which react selectively withthe reactive species. In fact the changes of the absorptionand the emission spectra of these molecules after the illuminationof the PS provide information on the specic ROS formation.The 1O2 formation has been tested using chemicalmethods based on the use of Uric Acid (UA), 9,10-diphenilanthracene(DPA) and Singlet oxygen sensor green (SOSG) andby direct detection of 1O2 luminescence decay at 1270 nm.Moreover, 2,7-dichlorouorescin and ferricytochrome c (CytFe3+) have been used to detect the formation of hydrogenperoxide and superoxide radical anion, which reduces Fe3+ ofthe ferricytochrome to Fe2+, respectively.