Biocompatible PEGylated bismuth nanocrystals: “All-in-one” theranostic agent with triple-modal imaging and efficient in vivo photothermal ablation of tumors

Biocompatible single-component theranostic agents integrating multimodal imaging and therapeutic functions (namely, "all-in one" agents) are highly desired for clinical cancer treatments. Herein, PEGylated pure metallic bismuth nanocrystals (Bi-PEG NCs) have been developed to be a competent theranostic agent for in vivo high-performance multimodal bio-imaging and photothermal ablation of tumors. The resultant Bi-PEG NCs show excellent physiological stability, biocompatibility, prolonged blood circulation half-life and preferential tumor accumulation. Thanking to the strong near-infrared (NIR) absorbance as well as the high photothermal conversion efficiency and conversion stability, highly effective in vivo photothermal ablation on tumors has been realized upon NIR irradiation, without noticeable toxicity. Impressively, the Bi-PEG NCs show ultrahigh X-ray computed topography (CT) enhancement efficiency (∼60.3 HU mL mg-1), overwhelming all CT contrast agents reported so far. Combining the strong CT contrast ability and photoacoustic/photothermal effect, high-contrast CT, photoacoustic (PA) and infrared thermal (IRT) triple-modal imaging have been demonstrated both in vitro and in vivo. This work highlights the potentials of such NCs as a powerful "all-in-one" theranostic nanoplatform for bioimaging and antitumor therapy, and may have provided a rather promising candidate for clinically-applied antitumor treatments based on single-component agents.