Graphene Quantum Dots-Coated Bismuth Nanoparticles for X-ray CT Imaging-Guided Photothermal therapy of Cancer Cells

Introduction: Theranostic nanoparticles, which integrate both diagnostic and therapeutic capabilities into one nanoagent, has great promise to ablate more effective tumoral tissue by optimizing and real-time monitoring treatment interventions, as well as monitoring therapeutic response to corresponding effect. Multifunctional theranostic nanoagent based on graphene quantum dots (GQDs)-coated Bi nanohybrids (GQDs-Bi NPs) was developed and investigate their multimodal imaging and PTT performance. Materials and Methods: The GQDs-Bi NPs were fabricated by utilizing simple two-step synthesis: GQDs as shell and Bi NPs as core in presence of GQDs. By hemolysis and MTT test, blood compatibility and cellular toxicity of GQDs-Bi NPs were examined. For phantom CT imaging, the GQDs-Bi NPs aqueous solutions at various concentrations of Bi element scanned by a clinical CT scanner (GE HiSpeed) (160 mA, 80,120 and140 kV). The corresponding CT values (HU) were measured by imageJ software. To evaluate the photothermal effect, the GQDs-Bi NPs dispersions at different concentrations of active Bi metal were irradiated with an 808 nm-NIR-laser (1.7 W·cm-2) for 10 min and a thermocouple probe was used to record the temperature of suspensions. Results: The GQDs-Bi NPs showed satisfactory cytotoxicity and hemolysis behavior. The heavy metal Bi component (Z=83) in the GQDs-Bi NPs produced much higher Hounsfield units (173 HU) than the contrast agents based on small molecules iodine (134 HU), corresponding, 1 mg Bi/ml provided an equivalent X-ray attenuation as dotarem contain of 1.5 mg/mL Iodine. A strong and steady absorbance was found for GQDs-Bi NPs in the whole NIR range, as well as high photo-to-thermal conversion capability and photostability, encouraging a high antitumor PTT efficiency. The GQDs-Bi NPs could successfully kill in vitro MCF-7 and HeLa cancer cells under NIR irradiation with killing effect dependent on dose compared to those received laser only (3.0%). Conclusion: GQDs-Bi nanotheranostic may become an effective tool for CT imaging-guided therapy for personalized cancer treatment.