Ultrafast Synthesis of Ultrasmall Poly(Vinylpyrrolidone)-Protected Bismuth Nanodots as a Multifunctional Theranostic Agent for In Vivo Dual-Modal CT/Photothermal-Imaging-Guided Photothermal Therapy

To elaborately fabricate real-time monitoring and therapeutic function into a biocompatible nanoplatform is a promising route in the cancer therapy field. However, the package of diagnosis and treatment into a single-"element" nanoparticle remains challenge. Herein, ultrasmall poly(vinylpyrrolidone)-protected bismuth nanodots (PVP-Bi nanodots) are successfully synthesized through an ultrafacile strategy (1 min only under ambient conditions). The nanodots are easy to synthesize in both laboratory and large scale using low-cost bismuth ingredients. PVP-Bi nanodots with ultrasmall size show good biocompatibility. Due to the high X-ray attenuation ability of Bi element, PVP-Bi nanodots have prominent performance on X-ray computed tomography (CT) imaging. Moreover, PVP-Bi nanodots exhibit a high photothermal conversion efficiency ( eta = 30%) because of the strong near-infrared absorbance, which can serve as nanotheranostic agent for photothermal imaging and cancer therapy. The subsequent PVP-Bi-nanodot-mediated photothermal therapy (PTT) result shows highly efficient ablation of cancer cells both in vitro and in vivo. PVP-Bi nanodots can be almost completely excreted from mice after 7 d. Blood biochemistry and histology analysis suggests that PVP-Bi nanodots have negligible toxicity. All the positive results reveal that PVP-Bi nanodots produced through the ultrafacile method are promising single-"element" nanotheranostic platform for dual-modal CT/photothermal-imaging-guided PTT.