Low Toxicity, High Resolution, and Red Tissue Imaging in the Vivo of Yb/Tm/GZO@SiO Core-Shell Upconversion Nanoparticles.

Lanthanide-doped upconversion nanoparticles (UCNPs) have attracted great attention in bioimaging applications. However, the stability and resolution of bioimaging based on UCNPs should be further improved. Herein, we synthesized SiO-coated Ga(III)-doped ZnO (GZO) with lanthanide ion Yb(III) and Tm(III) (Yb/Tm/GZO@SiO) UCNPs, which realized red fluorescence imaging in heart tissue. With increasing injection concentrations of Yb/Tm/GZO@SiO (1-10 mg/kg), the red fluorescence imaging intensity of heart tissue gradually increased. Moreover, the experimental results of toxicity in vitro and histological assessments of representative organs in vivo were studied, indicating that Yb/Tm/GZO@SiO UCNPs had low biological toxicity. These results proved that Yb/Tm/GZO@SiO can be used as a probe for fluorescence imaging in vivo.