Near-infrared photothermal therapy of Prussian-blue-functionalized lanthanide-ion-doped inorganic/plasmonic multifunctional nanostructures for the selective targeting of HER2-expressing breast cancer cells.

We report the synthesis, characterization, and application of Prussian blue (PB) functionalized CaMoO4:Eu@SiO2@Au nanorod hybrid nanoparticles (HNPs), with multimodal capabilities such as fluorescence imaging, surface-enhanced Raman spectroscopy (SERS) detection and photothermal therapy (PTT). The average size of CaMoO4:Eu@SiO2 NPs was 206 nm. The HNPs are highly dispersible in water for several weeks without settling and show a strong absorption in the near-infrared region, overlapping with the PB absorption between 600 nm and 1000 nm and the surface plasmon resonance of Au nanorods around 800 nm. Upon 808 nm laser excitation, HNPs show hyperthermia temperature (∼43 °C). Moreover, PB-functionalized NPs can be used in clinical trials for the treatment of radioactive exposure, and PB acts as a Raman reporter molecule (2152 cm-1 characteristic peak) with good biosafety and stability in the human body. In addition, coating the surface of CaMoO4:Eu NPs with both SiO2 and Au nanorods increases the biocompatibility of the HNPs. Furthermore, the PTT efficiency of human epidermal growth factor receptor 2 (HER2) antibody-conjugated HNPs on MDA-MB-435 cancerous cells was significantly higher than that of hepatocyte cells (noncancerous). This is due to the greater uptake of HNPs on cancerous cells than on noncancerous cells. Together, this study shows the potential applications of these HNPs in fluorescence imaging, SERS detection, and PTT functionalities with good photostability and biocompatibility.