Luminescent Ru(bpy)-doped silica nanoparticles for imaging of intracellular temperature.

Silica nanoparticles doped with the luminescent temperature probe Ru(bpy) were prepared by a modified Stöber method and are shown to enable optical sensing of intracellular temperatures. Based on the regrowth of silica nanoseeds, the ruthenium probe was easily incorporated and then covered with a shell of pure silica. The resulting nanothermometers were immune to the quenching by oxygen owing to the outer silica layer. The nanoparticles were further coated with poly-L-lysine in order to reduce cytotoxicity and to warrant cellular uptake. The luminescence of these nanosensors is rather sensitive to temperature in the physiological range (25-45 °C), with a decrease of −1.26 % in intensity per °C increase in temperature. The nanosensors were internalized into living cells of a hepatocellular carcinoma cell line along with gold nanorods. These display longitudinal surface plasmon resonance absorption at ~808 nm that causes a local rise in temperature. The microscopically captured luminescence intensity of the nanosensors after 808 nm irradiation of the gold nanorods decayed with increasing temperature, thereby indicating successful imaging of temperature. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]