O₂-Generating Fluorescent Carbon Dot-Decorated MnO₂ Nanosheets for "Off/On" MR/Fluorescence Imaging and Enhanced...

Imaging-guided photodynamic therapy (PDT) has emerged as a promising protocol for cancer theragnostic. However, facile preparation of such a theranostic system for simultaneously achieving tumor location, real-time monitoring, and high-performance reactive oxygen species generation is highly desirable but remains challenging. Herein, we developed a reasonable tumor-targeting strategy based on carbon dots (CDs)-decorated MnO₂ nanosheets (HA-MnO₂-CDs) with an active magnetic resonance (MR)/fluorescence imaging and enhanced PDT effect. Under light irradiation, the addition of HA-MnO₂-CDs increased the production of ¹O₂ by 2.5 times compared with CDs, providing favorable conditions for the PDT treatment effect on breast cancer. Moreover, HA-MnO₂-CDs exhibited excellent performance in producing O₂ in the presence of endogenous H₂O₂, which alleviated hypoxia in tumors and improved the therapeutic effect of PDT. In the presence of glutathione (GSH), the degraded MnO₂ nanosheets released CDs and Mn²⁺ from HA-MnO₂-CDs, restoring their fluorescence imaging function and increasing T₁ relaxivity (r₁) by 23 times. In vivo fluorescence and MR imaging suggested the excellent tumor-targeting property of HA-MnO₂-CDs. By combining the complementary properties of nanoprobes and tumor microenvironments, the in vivo PDT therapeutic effect was significantly improved under the action of HA-MnO₂-CDs. Overall, our reasonably designed HA-MnO₂-CDs may inspire the future development of the next generation of high-performance tumor-responsive diagnostic and therapeutic agents to further enhance the targeted therapy effect of tumors.