Gadolinium-chelate Functionalized Bismuth Nanotheranostic Agent For Diagnosis And Therapy In Cancer

ObjectiveMultifunctional gadolinium chelating bismuth nanotheranostic agent was prepared as the contrast agent for CT/PA/MR imaging and photothermal conversion agent,which was used for cancer treatment under the guidance of triple-modal imaging.Methods1.Peparation and Characterization:?1?A simple non-injection method was used to synthesize DT decorated hydrophobic Bi-NPs?DT-Bi NPs?.Then the outmost surface of DT-Bi NPs were further modified with amphipathic Gd-DTPA-BC6 and DSPE-PEG2000 by self-assembly method.?2?The morphology of nanoparticles was observed by TEM,the size distribution of nanoparticles was detected by DLS,and the near-infrared absorption capacity of nanoparticles was analyzed by ultraviolet absorption spectroscopy.?3?FTIR/XPS/XRD was used to characterize the structural characteristics of Gd-Bi-PEG NPs.?4?The toxicity of NPs in vitro was analyzed by MTT and hemolysis studies.2.Multi-modal imaging of CT/PAI/MRI imaging:?1?To evaluate the CT/PAI/MRI contrast efficiency in vitro,different concentration of Gd-Bi-PEG NPs was prepared and scanned by CT/PA/MR scanner.?2?To further study the contrast efficiency in vivo,Gd-Bi-PEG NPs was injected into tumor-bearing mice via tail vein.The mice were scanned at the different time.3.The efficiency of photothermal therapy:?1?Under irradiation,the temperature of different concentration of Gd-Bi-PEG NPs was recorded.After Gd-Bi-PEG NPs injection,the temperature of tumor area was measured at the different time point.?2?MTT and Live-dead staining evaluated the localized photothermal ablation capability of Gd-PEG-Bi NPs in vitro.?3?Tumor volume and tumor weight of tumor-bearing mice with different treatment methods were measured and TIR was calculated at the same time,and histochemical staining was performed on tumors and various important organs to analyze the photothermal treatment ability of Gd-Bi-PEG NPs.Results1.Preparation and Characterization:?1?Gadolinium chelated bismuth nanoparticles was synthesis successfully.?2?FTIR/XPS/XRD indicated the successful construction of Gd-Bi-PEG NPs from the chemical structure,which contained Bi elements and Gd elements.?3?TEM and DLS showed Gd-Bi-PEG NPs as a smooth spherical structure with an average hydration particle size of about 45 nm.Uv-vis absorption spectra demonstrated that the NPs had strong absorption in the near infrared region.?4?The cell viability of 200?g/mL Gd-Bi-PEG NPs was higher than 85%by MTT assay,and the hemolysis assay showed that the hemolysis rate of Gd-Bi-PEG NPs with higher concentration was lower than 5%.2.Multi-modal imaging of CT/PA/MR imaging:?1?The CT results in vitro showed that the X-ray absorption coefficient of Gd-Bi-PEG NPs was 38.4 HU mg/ml^-1,which was higher than Bi₂S₃ and iohexol,with better CT enhancement ability.The PAI results showed that Gd-Bi-PEG NPs with lower concentration?0.625 mg/mL?also had higher PA signal value?366 a.u?.In addition,the longitudinal relaxation rate of the NPs was 4.9mm^-1s^-1,which was similar to Magnevist and could improve the MRI enhancement effect.?2?The CT results in vivo showed that after 1 h Gd-Bi-PEG NPs injection,the CT value of tumor site in tumor-bearing mice reached the maximum value of 251.48±6.74 HU.The PAI in vivo results showed that after Gd-Bi-PEG NPs injection,the PAI effect of tumor site in tumor-bearing mice was significantly enhanced.The MRI in vivo results showed that the tumor-muscle ratio reached the maximum value of 2.56+0.10 after 1 h injection,and the MRI signal value was higher than the initial value even after 24 h,indicating that the NPs could significantly extend the imaging time window.3.The efficiency of photothermal therapy:?1?After 10 min irradiation,the temperature of 2 mg/mL Gd-Bi-PEG NPs increased⁴0?rapidly,and the photothermal conversion efficiency???was²8.4%in vitro.After Gd-Bi-PEG NPs injection?i.v?,the temperature of tumor area was increased from 26.2?to 53.2?.?2?in vitro MTT results showed that when C6 cells were co-cultured with 200?g/mL Gd-Bi-PEG NPs,the cell viability after NIR irradiation was 12.28%”:±0.71%.The results of living dead cells staining showed that most C6 cells were ablated when Gd-Bi-PEG NPs and NIR irradiation were combined to treat C6 cells.?3?Anti-tumor results showed that the TIR of tumor-bearing mice in the experimental group was101.72%±1.85%,and the tumor weight was 0.25±0.06 g,which had significantly difference with the control groups?p<0.0005,n=4?.In addition,HE staining results of the experimental group showed that there were almost no surviving tumor cells in the tumor area.Conclusion1.In this study,Gd-Bi-PEG NPs was successfully prepared,which had strong absorption capacity in the near infrared region,low toxicity and good biocompatible,and had great potential in application in vivo.2.In vitro and in vivo experiments confirmed that Gd-Bi-PEG NPs could significantly enhance the CT/PAI/MRI imaging effect,and was an ideal multi-modal imaging contrast agent.3.Gd-Bi-PEG NPs had significant photothermal conversion efficiency in vitro,and could achieve a better ability of photothermal ablation of C6 cells.In vivo,it could significantly increase the temperature of tumor site and obviously inhibited tumor growth in tumor-bearing mice,further indicating that this NPs can be applied to image-guided photothermal therapy and has potential clinical conversion potential.