NIR-to-NIR Deep Penetrating Nanoplatforms Y₂O₃:Nd³⁺/Yb³⁺@SiO₂@Cu₂S toward Highly Efficient Photothermal Ablation

A difunctional nano-photothermal therapy (PTT) platform with near-infrared excitation to near-infrared emission (NIR-to-NIR) was constructed through core-shell structures Y₂O₃:Nd³⁺/Yb³⁺@SiO₂@Cu₂S (YRSC), in which the core Y₂O₃:Nd³⁺/Yb³⁺ and shell Cu₂S play the role of bioimaging and photothermal conversion function, respectively. The structure and composition of the present PTT agents (PTAs) were characterized by powder X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectra. The NIR emissions of samples in the biological window area were measured by photoluminescence spectra under the excitation of 808 nm laser; further, the penetration depth of NIR emission at different wavelengths in biological tissue was also demonstrated by comparing with visible (vis) emission from Y₂O₃:Yb³⁺/Er³⁺@SiO₂@Cu₂S and NIR emission from YRSC through different injection depths in pork muscle tissues. The photo-thermal conversion effects were achieved through the outer ultrasmall Cu₂S nanoparticles simultaneously absorb NIR light emission from the core Y₂O₃:Nd^3+/Yb³⁺ and the 808 nm excitation source to generate heat. Further, the heating effect of YRSC nanoparticles was confirmed by thermal imaging and ablation of YRSC to Escherichia coli and human hepatoma (HepG-2) cells. Results indicate that the YRSC has potential applications in PTT and NIR imaging in biological tissue.