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 (η = 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.