Size-Dependent Photodynamic Activity of Gold Nanoparticles Conjugate of Water Soluble Purpurin-18-N-Methyl-D-Glucamine

Gold nanoparticles (GNPs) conjugates of water soluble ionic photosensitizer (PS), purpurin-18-N-methyl-D-glucamine (Pu-18-NMGA), were synthesized using various molar ratios between HAuCl4 and Pu-18-NMGA without adding any particular reducing agents and surfactants. The PS-GNPs conjugates showed long wavelength absorption of range 702–762 nm, and their different shapes and diameters depend on the molar ratios used in the synthesis. In vitro anticancer efficacy of the PS-GNPs conjugates was investigated by MTT assay against A549 cells, resulting in higher photodynamic activity than that of the free Pu-18-NMGA. Among the PS-GNPs conjugates, the GNPs conjugate from the molar ratio of 1 : 2 (Au(III): Pu-18-NMGA) exhibits the highest photodynamic activity corresponding to bigger size (~60 nm) of the GNPs conjugate which could efficiently transport the PS into the cells than that of smaller size of the GNPs conjugate.