Core–Shell Rare Earth Nanoparticles for Photochemo-Dynamic Cancer Theranostics under NIR Excitation

Photodynamic therapy (PDT) is an effective strategy for cancer treatment, which offers advantages such as rapid effectiveness, low toxicity, and minimal trauma. However, one of the key components of PDT, photosensitizers, typically requires excitation by ultraviolet or visible light to function, which limits the application of this therapy to some extent. To address the above issues, in this research, a composite material UCNPs@SiO2–ZnPc-Fe(OH)3 (USZ-Fe(OH)3) was prepared for photochemo-dynamic therapy (PCDT) based on rare earth upconversion nanoparticles (UCNPs). To enhance the upconversion fluorescence intensity, a layer of inert shell was coated on the original nanoparticles, resulting in core–shell–shell-structured UCNPs of NaYF4:Yb,Er@NaYF4:Nd@NaYF4. A layer of SiO2 was coated on the above UCNPs in order to improve their biocompatibility, followed by loading the photosensitizer ZnPc to prepare UCNPs@SiO2–ZnPc (USZ) for PCDT of oral squamous cell carcinoma (OSCC). Finally, Fe(OH)3 was loaded on the surface of USZ through electrostatic adsorption to obtain USZ-Fe(OH)3, with the aim of improving the hypoxic environment in solid tumors and achieving the effectiveness of PCDT. In vitro and in vivo experiments demonstrated the composite material USZ-Fe(OH)3 exhibited excellent therapeutic effects in PCDT for OSCC. Moreover, a deep learning model of the ResNet18 network was used to detect the pathology of the tumor area from mice treated with PCDT and those from the control group. All of the results indicate the proposed PCDT platform in this work presented excellent performance in tumor treatment.