Hollow Mesoporous Prussian Blue Nanoparticles for In Vivo Synergistic Chemo-Photothermal Cancer Therapy and Dual-Mode Magnetic Resonance/Fluorescence Imaging

The development of a theranostic platform that integrates multiple modalities into a single entity is a hopeful approach for effective cancer treatment but still a challenge. This study presents a smart and versatile theranostic nanoplatform for remarkably potent in vivo synergistic chemo-photothermal tumor treatment, guided by MR/fluorescence dual-mode imaging utilizing a pH-responsive strategy. We encapsulated Gd3+-based carbon quantum dots (GCDs) and doxorubicin (DOX) within hollow mesoporous Prussian blue nanoparticles (HMPB NPs). This innovative theranostic platform, named DOX/GCDs-HMPB NPs, facilitates targeted drug release and simultaneous MR/fluorescence imaging, specifically at the tumor site. At physiological pH, both GCDs and DOX molecules are encapsulated within the mesoporous hollow network of the nanoparticles, with the metal–ligand coordination bonding between Gd species and DOX molecules, to restrict water molecules' access to the Gd3+ center, thus minimizing proton relaxivity. In the acidic tumor microenvironment, GCDs and DOX drug molecules are released simultaneously from the nanoparticles and enhance both MR contrast and fluorescence, leading to an increase in chemotherapeutic activities. This system reveals strong pH-switching theranostic performance for 4T1 cells, with high-efficiency chemotherapy and considerable photothermal conversion, indicating practical application for synergistic chemo-photothermal treatment of tumors. A promising strategy for developing a theranostic platform for cancer treatment and diagnosis is introduced.