Generation of cytotoxic singlet oxygen via phthalocyanine-stabilized gold nanoparticles: A potential delivery vehicle for photodynamic therapy

Gold nanoparticles have been stabilized with a phthalocyanine (Pc) photosensitizer. Transmission electron microscopy confirmed that the coated particles were in the 2-4 nm size regime. Energy-dispersive X-ray analysis revealed that the Pc macrocycle was present on the gold surface and also that the TOAB phase transfer reagent, used during the synthesis, was associated with the nanoparticles. The three-component (photosensitizer/gold/phase transfer reagent) nanoparticles were shown to generate singlet oxygen with enhanced quantum yields as compared to the free Pc. Additionally, the association of the transfer reagent promoted the solubility of the surface-bound hydrophobic sensitizer in polar solvents which would facilitate their systemic injection. The results suggest that these three-component structures have potential as a useful vehicle for the delivery of photosensitizer agents in photodynamic therapy.