`Folate-Conjugated Phosphorescent Silica Nanoparticles for Bioimaging and Cancer Cell Targeting.

Besides their superior photophysical properties, phosphorescent transition-metal complexes have some drawbacks for biological applications because of their poor solubility in aqueous solutions and toxicity. In order to avoid the biological environmental impacts on their optical function and solve the problems of water-solubility and toxicity in sensing and bioimaging, two biocompatible organic/inorganic hybrid phosphorescent nanoprobes (Ir-MSN) by using mesoporous silica nanoparticles (MSN) as carriers and an iridium(III) complex as signaling unit were prepared in the present study. In addition, folic acid (FA) was covalently attached to them to endow the particles with characteristic of tumor targeting. The photophysical properties, cell staining and tumor cell targeting functions of FA-ligated Ir-MSN were investigated. These results demonstrated that such a design strategy of phosphorescent nanoprobes is an effective way to develop excellent phosphorescent cellular probes for living cell applications.