Multifunctional nanomaterials with integrated diagnostic and therapeutic functions, combination therapy to enhance treatment efficacy, as well as low toxicity have drawn tremendous attentions. Herein, we report a multifunctional theranostic agent based on peptide (LyP-1)-labeled ultrasmall semimetal nanoparticles of bismuth (Bi-LyP-1 NPs). Ultrasmall Bi NPs (3.6 nm) were facilely synthesized using oleylamine as the reducing agent and exhibited a higher tumor accumulation after being conjugated with the tumor-homing peptide LyP-1. The abilities to absorb both ionizing radiation and the second near-infrared (NIR-II) window laser radiation ensured that Bi-LyP-1 NPs are capable of dual-modal computed tomography/photoacoustic imaging and efficient synergistic NIR-II photothermal/radiotherapy of tumors. Moreover, Bi-LyP-1 NPs could be rapidly cleared from mice through both renal and fecal clearance and almost completely cleared after 30 days. Such multifunctional nanoparticles as efficient cancer theranostic agents, coupled with fast clearance and low toxicity, shed light on the future use of semimetal nanoparticles for biomedicine.
Keywords: bismuth; multimodal imaging; semimetal nanoparticles; the second near-infrared (NIR-II) window; thermoradiotherapy.