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Non‐invasive theranostics that integrate the advantages of multimodality imaging and therapeutics have great potential in the field of biomedicine. Herein, a new nanohybrid based on Bi2Se3‐conjugated upconversion nanoparticles (UCNPs) has been successfully developed through a simple in situ growth strategy. Under 808 nm near‐infrared laser irradiation, the UCNPs can emit bright visible light, whereas the Bi2Se3 nanomaterial exhibits efficient photothermal conversion capacity. Moreover, the as‐synthesized UCNP–Bi2Se3 nanohybrid exhibits efficient cell upconversion luminescence (UCL), reasonable CT imaging, and admirable cancer cell ablation capacity, further emphasizing the efficiency of this strategy for simultaneous UCL imaging and photothermal therapy. The designed theranostic strategy guided by dual‐modal imaging endowed with real‐time dynamic monitoring, remote controllability, and non‐invasiveness makes the UCNP–Bi2Se3 nanohybrid an ideal candidate for non‐invasive multimodal imaging‐guided photothermal therapy for the precise diagnosis and treatment of cancer. [ABSTRACT FROM AUTHOR]

Lanthanide-doped upconversion nanoparticles (UCNPs)-based active targeting optical bioimaging has attracted tremendous scientific interest because of its noninvasive real-time signal feedback, superior tissue penetration depth and high spatial resolution in early diagnosis of disease. Herein, we synthesize a novel carboxy-terminated silica coated NaErF 4 : 10% Yb@NaYF 4 : 40% Yb@NaNdF 4 : 10% Yb@NaGdF 4 : 20% Yb UCNPs (termed as UCNP@SiO 2 -COOH) with 808 nm near-infrared (NIR) excitation and bright 655 nm upconversion luminescence (UCL) emission for realizing deep tissue imaging. Under 808 nm NIR laser excitation (1.5 W cm−2), the UCL of UCNP@SiO 2 -COOH with relative low concentration (2 mg mL−1) can be successfully visualized under a chicken breast slice with 10 mm thickness. After conjugated with various molecules including NH 2 -PEG 3400 -COOH, peptide D-SP5 and Uelx Europaeus Agglutinin-I (UEA-I), biodistributions, clearance pathways and tumor-targeting capacities of the UCNP@SiO 2 -COOH and corresponding bioconjugates (termed as UCNP@SiO 2 -PEG, UCNP@SiO 2 -D-SP5 and UCNP@SiO 2 -UEA-I, respectively) were investigated by tracking the UCL intensities of livers, kidneys and tumors. Both of in vitro and in vivo experimental results reveal that there is no significant difference for their in vivo biodistributions and clearance pathways. The UCNP@SiO 2 -UEA-I exhibits much higher SW480 tumor-targeting capacity than those of other bioconjugates. In particular, the as-prepared UCNP@SiO 2 -UEA-I even to visualize ultrasmall (c.a. 3 mm3 in volume) subcutaneous SW480 tumor in Balb/c nude mouse through intravenous administration. The study implies that the red UCL emitted UCNPs with a minimized heating effect is suitable for deep tissue biomedical imaging and UCNP@SiO 2 -UEA-I can serve as an efficient optical probe for early diagnosis of SW480 tumor. Image 1 [ABSTRACT FROM AUTHOR]