Enhancing Osteosarcoma Killing and CT Imaging Using Ultrahigh Drug Loading and NIR-Responsive Bismuth Sulfide@Mesoporous Silica Nanoparticles.

Despite its 5-year event-free survival rate increasing to 60-65% due to surgery and chemotherapy, osteosarcoma (OS) remains one of the most threatening malignant human tumors, especially in young patients. Therefore, a new approach that combines early diagnosis with efficient tumor eradication and bioimaging is urgently needed. Here, a new type of mesoporous silica-coated bismuth sulfide nanoparticles (Bi2 S3 @MSN NPs) is developed. The well distributed mesoporous pores and large surface areas hold great promise for drug protection and encapsulation (doxorubicin (DOX), 99.85%). Moreover, the high photothermal efficiency of Bi2 S3 @MSNs (36.62%) offers great possibility for cancer synergistic treatment and highly near-infrared-triggered drug release (even at an ultralow power density of 0.3 W cm-2 ). After covalently conjugated to arginine-glycine-aspartic acid (RGD) peptide [c(RGDyC)], the NPs exhibit a high specificity for osteosarcoma and finally accumulate in the tumor cells (tenfold more than peritumoral tissues) for computed tomography (CT) imaging and tumor ablation. Importantly, the synergistic photothermal therapy-chemotherapy of the RGD-Bi2 S3 @MSN/DOX significantly ablates the highly malignant OS. It is further proved that the superior combined killing effect is achieved by activating the mitochondrial apoptosis pathway. Hence, the smart RGD-Bi2 S3 @MSN/DOX theranostic platform is a promising candidate for future applications in CT monitoring and synergistic treatment of malignant tumors.