Engineering Near-Infrared-Excitable Metal-Organic Framework for Tumor Microenvironment Responsive Therapy

Luminescent metal-organic frameworks (MOFs), which incorporate some guest luminescent molecules/ions into MOFs, have attracted extensive attention because of their exceptional optical properties. However, traditional luminescent MOFs are mainly responsive to ultraviolet (UV) or visible light, which has limited their bioapplications due to the restrained tissue penetration depths. In this study, we have constructed a diagnostic nanoplatform UCNP@MOF consisting of upconverting metal-organic frameworks, which combine the photo-upconverting characteristics of the upconversion nanoparticles (UCNPs) with the unique physicochemical properties of Al-MOFs. Specifically, the core-shell structured UCNP@MOF nanocomposites were prepared by poly(vinylpyrrolidone) (PVP)-regulated nucleation of Al-MOF layer on the UCNP surface. When excited by a 980 nm laser light, the green signal released from UCNPs can trigger the photosensitive Al-MOFs to produce a large amount of singlet oxygen (¹O₂) for photodynamic therapy (PDT). Meanwhile, the anticancer drug, doxorubicin hydrochloride (DOX), was further incorporated into the porous structures of Al-MOFs and demonstrated the pH-responsive drug release behavior. Our results show that the near-infrared (NIR) light-induced PDT with chemotherapy (CMT) exhibits excellent antitumor effects. It is believed that the present work highlights the potential of the combination of UCNPs and MOFs and holds great promise for biomedical applications.