A dual-fluorescent nano-carrier for delivering photoactive ruthenium polypyridyl complexes

Abstract

A dual-fluorescent nanocarrier was synthesized by coating human serum albumin (HSA) on lanthanide-doped upconversion nanoparticles (UCNPs). The HSA coating makes the particles highly biocompatible and well dispersed in aqueous solutions. This nanocarrier demonstrates two types of fluorescence: the blue upconversion fluorescence under excitation with a 980 nm light of the UCNP core, and the green fluorescence under the excitation with a 450 nm light of the polymerized HSA layer. This dual-fluorescence property makes the material more applicable in bio-imaging. A photo-sensitive ruthenium complex ([Ru(bpy)₂(dmbpy)₂]Cl₂, Ru-1) was loaded to generate the light-responsive Ru-HSA-UCNPs. This conjugate showed very low inhibitory effect on cell proliferation in the dark, while light irradiation significantly enhanced its cytotoxicity to cancer cells. Further investigations showed that irradiation activated Ru-1 and the product became highly reactive to DNA. This result suggests the potential application of this conjugate in the controlled release of active anticancer agents in tumor sites.