Development of chemically synthesized spherical plasmonic LaB6 nanoparticles for biomedical applications

Abstract LaB6 is a unique plasmonic material, for which the localized surface plasmon resonance (LSPR) absorption band intrinsically lies in the near infrared (NIR) region. In this work, we synthesized spherical LaB6 nanoparticles with a tunable size within 50–200 nm. The optical properties of these LaB6 nanospheres were found to be sensitive to the thickness of surface oxide layer that was formed during the synthesis, purification and dispersion processes. In order to enhance the stability of LaB6 nanoparticles in aqueous environment, LaB6@SiO2 with a core-shell structure was successfully prepared. Both LaB6 and LaB6@SiO2 demonstrated low cytotoxity in biomedical tests when their concentrations were limited to 0.2 mg mL−1. The in vitro photothermal therapy experiment showed that 4T1 cancer cells were eventually apoptotic after being exposed to a 980 nm laser for 5 min at a considerably low power density of 0.82 W cm−2 and a low dose of 0.1 mg mL−1 for LaB6@SiO2. The results suggest that these LaB6 nanospheres are viable photothermal agents for biomedical applications.