O₂-Generating Fluorescent Carbon Dot-Decorated MnO₂ Nanosheets for “Off/On” MR/Fluorescence Imaging and Enhanced Photodynamic Therapy

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 MnO 2 nanosheets (HA-MnO 2 –CDs) with an active magnetic resonance (MR)/fluorescence imaging and enhanced PDT effect. Under light irradiation, the addition of HA-MnO 2 –CDs increased the production of 1 O 2 by 2.5 times compared with CDs, providing favorable conditions for the PDT treatment effect on breast cancer. Moreover, HA-MnO 2 –CDs exhibited excellent performance in producing O 2 in the presence of endogenous H 2 O 2, which alleviated hypoxia in tumors and improved the therapeutic effect of PDT. In the presence of glutathione (GSH), the degraded MnO 2 nanosheets released CDs and Mn 2+ from HA-MnO 2 –CDs, restoring their fluorescence imaging function and increasing T 1 relaxivity ( r 1 ) by 23 times. In vivo fluorescence and MR imaging suggested the excellent tumor-targeting property of HA-MnO 2 –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-MnO 2 –CDs. Overall, our reasonably designed HA-MnO 2 –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.