Preparation And Application Of Nuclear Medicine Imaging Nanoprobes Based On Functional Inorganic Nanoparticles

Background:Nuclear medicine imaging(NMI)has garnered great attention since its enormous potentials as part of multimodality imaging in the accuracy diagnosis of tumors have been well demonstrated.An appropriately designed radioactive nanoprobe acting as the signal source is always in need in this scenario.Hence,to develop an advanced radiolabeling method for better construction of nanoprobes is of paramount significance.Among the various reported methods for radiolabeling nanomaterial,Ligand Anchoring Group MEdiated RAdioLabeling(LAGMERAL)method stands out because of its easy operability,high efficiency and excellent stability,which endows it with great possibility on further exploration and application.Nevertheless,for this innovative labeling method,the suitable ranges of radionuclides and nanoparticles remain unclear,and the potentials of resulting radioactive nanoprobes for disease diagnosis still need to be carefully evaluated,which is of great significance to improve the development and clinical translation of radioactive nanoprobes.Additionally,it is worth noticing that the large accumulation of nanoparticles in liver after intravenous administration will not only greatly suppress the effective delivery to target lesions,but also lead to increased toxicity to the cells,and this case is especially true for the radiolabeled nanoprobes.However,to the best of our knowledge,the distribution of nanoparticles on cell level in the liver have been barely studied,and much less about the complicated regulation of the cellular uptake of nanoparticles regarding the distinctive physicochemical properties such as the size and surface modification of nanoparticles.Objective:To explore the scope of the LAGMERAL method in metal radionuclides and functional inorganic nanoparticles,ecaluate the in vivo imaging performance and application prospect of the resulting radioactive nanoprobes,and lay experimental foundation for the clinical translation.To investigate the effect regularity of size and PEG chain length on the hepatocellular uptake of Fe3O4 nanoparticles,to provide theoretical basis for the construction of high performance radioactive nanoprobes.Method:Firstly,to explore the universality of LAGMERAL in inorganic nanoparticles composed of different metal elements and metal radionuclides distinct chemically,we firstly chose Fe3O4,NaGdF4:Yb,Tm,and Cu2-xS nanoparticles with inherent functions and broad application prospects in magnetic resonance imaging(MRI),upconversion luminescence(UCL)imaging and photoacoustic imaging(PAI),respectively.Followed synthesis through high temperature thermal decomposition,based on the strong binding affinity of bisphosphonate to metal ions,the abovementioned hydrophobic nanoparticles were successfully transferred to the aqueous phase via ligand exchange,followed by radiolabeling of transition metal radionuclide 99mTc,main group metal radionuclide 68Ga and lanthanide Metal radionuclide 177Lu,which are widely used in SPECT imaging,PET imaging and radiotherapy in clinic.Meanwhile,the influence of the radiolabeling process on the physicochemical properties of nanoparticles,the effect regularity of radionuclide type on the radiolabeling rate,and the radiolabeling stability of the obtained nanoprobes were also studied.In the second part,we further evaluated the synergistic diagnostic effect of the prepared radioactive nanoparticles in passive targeting SPECT/MRI of glioma tumor,active targeting SPECT/UCL of colorectal cancer,and SPECT/PAI of lymphatic metastasis.In the final part of the paper,we designed and synthesized different sized(i.e.,3.6 nm and 12.0 nm)Fe3O4 nanoparticles with different surface modifications(i.e.,PEG 1K,PEG 2K,and PEG5K with molecular weights of 1000,2000,and 5000,respectively,diphosphonate terminated),and effectively labeled the resulting nanoparticles with 99mTc based on LAGMERAL method.Subsequently,the uptake of nanoparticles by the main primary cells of the liver was quantitatively detected and analyzed,including hepatic parenchymal cells(Hepatocyte,HCs),liver sinusoidal endothelial cells(LSECs),and hepatic macrophages(Kupffer cells,KCs).Results:Through the LAGMERAL method,we achieved efficient radiolabeling of 99mTc,68Ga,and 177Lu on Fe3O4,NaGdF4:Yb,Tm,and Cu2-xS nanoparticles.The results show that this facile radiolabeling process has negligible effect on the phytochemical properties of the underlying nanoparticles with a negative correlation of radiolabeling rate and half-lives of radionuclides being disclosed,demonstrating the universality of LAGMERAL method in versatile inorganic nanoparticles and metal radionuclides.The in vivo imaging results show that the radioactive tracers are capable of forming diagnostic images as expected,in which the NMI matches well with the other modality imaging of nanoparticles,exhibiting the satisfied stability of all the asconstructed radiolabeled nanoprobes and their outstanding potential in sensitive diagnosis of tumor.Additionally,benefiting from the accurate quantitative characteristics of radionuclides,dynamic information about the pharmacokinetic behavior and biodistribution of nanoparticles can be conveniently obtained for providing guidance for further design and clinical translation of NMI nanoprobes.The uptake results show that when the PEG chain length was fixed,the cell uptake of 12.0 nm Fe3O4 nanoparticles was more than that of 3.6 nm counterparts for all three types of cells,while when the size of nanoparticles was the same,the PEG chain length dependence of different cells was never the same again.For HCs,PEG 2K modified nanoparticles exhibited lower uptake in both sized nanoparticles,while LSECs and KCs showed increased uptake with the increase of PEG chain length for 3.6 nm nanoparticles,but exact opposite for 12.0 nm ones.Moreover,we found a tendency that the uptake of nanoparticles at single cell level decreased from HCs to LSECs to KCs,regardless of the size and surface modification.The difference in uptake capacity may be closely related to the type of the receptors and density of clathrin-coated pits on the cell surface,as well as the type of protein corona on the nanoparticle.Conclusion:We demonstrate the universality of the LAGMERAL method based on representative functional inorganic nanoparticles and radionuclides,and verifies the great potential of the resulting radioactive nanoprobes for tumor imaging.Meanwhile,the interaction of major cells in the liver with Fe3O4 nanoparticles with different sizes and surface modifications was systematically investigated in vitro for the first time based on LAGMERAL method,which not only provides valuable information for deeper understanding of the distribution behaviour of nanoparticles in vivo,but also provides new ideas for the design and construction of nanoprobes.