Preparation of Tetraamino-phthalocyanine-Zinc-Loaded Silica Nanoparticles and Study of Their Cytotoxicity

Positively charged silica nanoparticles, entrapping the hydrophobic photosensitizer 2,9,16,23-tetraamino-phthalocyanine zinc (ZnPc(NH2)4), have been synthesized in the nonpolar core of micelles by hydrolysis of triethoxyvinylsilane and 3-aminopropyltriethoxysilane. The surface morphologies, charge state, solublility in water and stability have been characterized using transmission electron microscopy, dynamic light scattering technique, and ultraviolet-visible absorption spectra. The as-prepared nanoparticles are highly monodispersed spheres with uniform diameter (about 20 nm), which are stable in an aqueous system. Their average ζ-potential value is (28.8 ± 2.79) mV, and they show strong absorption peaks at 714 nm. In addition, encapsulation of ZnPc(NH2)4 in silica nanoparticles prevents leakage of ZnPc(NH2)4 and enhances the resistance to photobleaching. The ZnPc(NH2)4-entrapped-silica nanoparticles (SiO2@ZnPc(NH2)4) can efficiently generate singlet oxygen, as measured using the chemical probe 1,3-diphenylisobenzofuran. The cytotoxicity of silica nanoparticles has been investigated by incubation of both the ZnPc(NH2)4-entrapped-silica nanoparticles and the nanoparticles without ZnPc(NH2)4 (SiO2-NH2) but containing living cancer cells (HeLa, U251 and PC-12). The experimental result shows that neither SiO2@ZnPc(NH2)4 nor SiO2-NH2 particles have significant cytotoxicity when the concentration of the particles is lower than 300 mg L−1.