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

• The intelligent composite nanoparticles of LNPs-Au were carefully constructed. • The LNPs-Au can act a nano temperature probe in living body using FIR technique. • The LNPs-Au achieved controllable PTT based on accurate temperature detection. • The LNPs-Au with emission in NIR II achieved fluorescence imaging of deep tissue. 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. [ABSTRACT FROM AUTHOR]