Core-Shell Colloidal Nanocomposites for Local Temperature Monitoring during Photothermal Heating

Determining temperature changes at the heating site to accurately control thermal treatments has been a major goal in the field of nanothermometry. In this study, we address the need to effectively monitor local temperature during the application of photothermal therapies, which is essential to prevent uncontrolled heating induced by nanoparticle sensitizers used in such treatments. For this purpose, we developed a synthetic protocol to produce a nanocomposite probe that allows local photothermal heating and simultaneous in situ optical nanothermometry, within the biological transparency windows. The nanocomposite material comprises gold nanorods for light-to-heat conversion and neodymium (Nd3+)-based nanoparticles for local temperature monitoring. An inert spacer made of mesoporous silica provides a core-shell structure and ensures uniform separation between both functionalities to prevent photoluminescence quenching. By using an 808 nm laser as the source for both heating and photoluminescence excitation, we demonstrate a direct correlation between local temperature and near-infrared Nd3+ emission intensities, thereby providing precise local temperature monitoring. Different levels of local heating were studied by varying the incident laser power, resulting in a maximum temperature increase of 47 degrees C detected with the nanothermometers. Albeit presented here as a proof of concept, this configuration can be translated to the design of materials for photothermal therapy.