Prussian blue-coated lanthanide-doped core/shell/shell nanocrystals for NIR-II image-guided photothermal therapy

Lanthanide-doped nanoparticles have long been stereotyped for optical luminescence bioimaging. However, they are known to be unable to produce therapeutic abilities. Here, we describe a lanthanide-based theranostic agent, namely, prussian blue (PB)-coated NaErF4@NaYF4@NaNdF4 core/shell/shell nanocrystals encapsulated in a phospholipid PEG micelle (PEG-CSS@PB), which showed switched imaging and hyperthermia abilities under distinct near infrared (NIR) light activation. The erbium (Er3+)-enriched inner core nanocrystals (NaErF4) enabled the emission of tissue-penetrating luminescence (1525 nm) in the second biological window (NIR-II, 1000-1700 nm), which endowed high-resolution optical imaging of the blood vessels and tumors under similar to 980 nm excitation. High neodymium (Nd3+) concentrations in the epitaxial outer NaNdF4 shell introduced maximum cross relaxation processes that converted the absorbed NIR light (similar to 808 nm) into heat at high efficiencies, thus providing abilities for photothermal therapy (PTT). Importantly, the coated Prussian blue (PB) increased light absorption by about 10-fold compared to the composite free of PB, thus entailing a high light-to-heat conversion efficiency of similar to 50.5%. This commensurated with that of well-established gold nanorods. As a result, the PEG-CSS@PB nanoparticles with MTT-determined low toxicities resulted in similar to 80% death of HeLa cells at a dose of 600 mu g mL(-1) under 808 nm laser irradiance (1 W cm(-2)) for 10 min. Moreover, utilizing the same light dose, a single PTT treatment in tumor-bearing BALB/c mice shrunk the tumor size by similar to 12-fold compared to the tumors without treatment. Our results, here, constituted a solid step forward to entitle lanthanide-based nanoparticles as theranostic agents in nanomedicine studies.