Mesoporous Manganese Dioxide-Coated Upconversion Nanoparticles for Smart Photoluminescence and Drug Delivery

A novel multifunctional nanoplatform (UCNP@MnO2 NPs) is proposed by combining the upconversion luminescence with glutathione (GSH)-responsive performance of mesoporous MnO2. The active core-shell upconversion nanoparticles (UCNPs) were prepared by high-temperature pyrolysis and seed epitaxial growth methods. Subsequently, the UCNPs were modified and further coated with a mesoporous MnO2 shell. Moreover, the UCNP@MnO2 NPs were further supported by various forms of structural characterization methods. As an effective photoluminescence nanoplatform, relying on the fluorescence performance of UCNP, the mesoporous MnO2 shell was designed as a fluorescence quencher and served as a GSH/H2O2 recognizer. The results indicate that the UCNP@MnO2 NP has excellent fluorescence quenching and recovery performance. Additionally, the mesoporous MnO2 shell of the UCNP@MnO2 NP is conducive to drug loading and release as a nanocarrier for drug delivery. As a result, the UCNP@MnO2 NPs demonstrated satisfying drug-loading efficiency (ca. 55.98%) and GSH-responsive controlled drug release. The UCNP@MnO2 NPs cumulatively released up to ca. 56.49% at GSH concentrations of 10 mM within 24 h. Furthermore, the UCNP@MnO2 NPs exhibited an excellent degradation performance. Overall, this study suggests a novel nanoplatform for smart photoluminescence and drug delivery, which offers unique insights and guidance for fluorometric imaging, sensing, and treatment.