Complexes of functionalized quantum dots and chlorin e6 in photodynamic therapy

Abstract

Recently, it has been suggested that quantum dots (QDs) could be used in the photodynamic therapy of cancer as resonance energy donors for conventional porphyrin type photosensitizers. Here we present the results of the spectroscopic studies on the formation of a non-covalent complex between QDs and photosensitizer chlorin Ce6 in an aqueous medium and in the presence of bovine serum albumin (BSA). Changes in the absorption and fluorescence spectra of QDs and Ce6 revealed the formation of a QD-Ce6 complex which occurs due to hydrophobic interaction between the nonpolar moiety of an amphiphilic photosensitizer and the hydrophobic part of the lipid-based coating of the QD. The photosensitizer conjugated with the QD could be indirectly excited by the Forster resonance energy transfer (FRET) from the QD to Ce6. The investigation on the capacity of such complex to generate 1O2 showed that the QD-Ce6 complex irradiated by visible light is able to produce 1O2 more efficiently than QDs or Ce6 taken separately. The photoinactivation of cells incubated with the QD-Ce6 complex and irradiated in the spectral region where the photosensitizer does not absorb provided evidence that such complex could induce FRET-mediated cell destruction.