Robust emission in near-infrared II of lanthanide nanoprobes conjugated with Au (LNPs-Au) for temperature sensing and controlled photothermal therapy

To address the poor activity and inaccurate in situ temperature measurements of composite photothermal probes, herein we report lanthanide nanoparticles-gold (LNPs-Au) nanoprobes for fluorescence temperature sensing and controlled photothermal therapy (PTT). The conjugation between LNPs and Au is done via electrostatic interactions. LNPs doped with rare earth cations (Yb3+, Ho3+, Er3+, and Ce3+) fluoresce strongly in the NIR-II region and their emission spectrum does not overlap with the absorption spectrum of Au. The intensities of LNPs-Au emission peaks at 1185 and 1560 nm highly depend on temperature, which is utilized in this study for the non-contact temperature measurements in the biologically relevant range. Deep tissue penetration of NIR-II radiation is observed, which is favorable for real-time temperature sensing. In addition, this radiation does not damage the normal tissue. Moreover, LNPs-Au nanoparticles reduce HeLa cell viability below 40 % and adequately inhibited tumor tissue in mice upon 808-nm irradiation. The results of this study will motivate the development of multifunctional photothermal probes for safer, controllable PTT of cancers with simultaneous temperature monitoring.