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.