Preparation And Study Of Dual-Mode Imaging Magnetic Carbon-Based Composite Particles

Fe3O4 possess mature preparation technology,with morphology and size are controllable.It can obtain specific properties by surface modification.It is widely used in magnetic resonance imaging due to its unique magnetic properties and biocompatibility.Magnetic resonance imaging(MRI)is a safe and non-destructive detection technology with high spatial resolution,which can be used for whole body detection.But its sensitivity is insufficient,which causes certain limitations for the detection of small lesions.Carbon quantum dots are novel nanomaterials in fluorescence(FL)imaging,with wide sources,low cost,low toxicity,good optical stability,and easy functionalization.By combining them,a magnetic fluorescence dual-modal imaging platform can be constructed to achieve functional complementarity and improve the accuracy of early detection,and then can also utilize photothermal or magnetocaloric effects to achieve PDT,PTT and magnetocaloric therapy.In this thesis,carbon quantum dots doped with different nitrogen sources and iron tetroxide modified with different electrical molecules were prepared by hydrothermal method and co-precipitation method,respectively.Their structures and properties were studied and used to construct FL/MR dual-mode imaging platform.The main research contents of this thesis are as follows:Firstly,carbon quantum dots modified with different nitrogen sources were prepared by one-step hydrothermal method.It was found that PEI-NCQDs had better fluorescence properties.Dimethylformamide(DMF)and polyethylene imine(PEI)had synergistic effect on improving the fluorescence intensity of PEI-NCQDs quantum dots as dinitrogen source doping.Then,the structure and properties of Fe3O4 modified by different electrical molecules were studied by coprecipitation method.It was found that the magnetic properties of Fe3O4 were affected by the content of surface modifier,and the type of surface molecules affected its stability and surface potential.After that,high fluorescence intensity diazo-doped carbon quantum dots PEINCQDs and Fe3O4 were selected to construct FL/MRI dual-mode imaging platform through electrostatic interaction.In vitro MRI showed that it had T2 contrast effect with relaxation rate of 31.09 mM-1s-1,but the fluorescence intensity needed to be improvedIn order to improve this,FL/MRI dual-mode imaging platform was further constructed by emulsion method.Through fluorescence and in vitro MRI,the prepared magnetic fluorescence material has good fluorescence properties and T2 relaxation efficiency,and is a potential contrast agent for dual-mode imaging.In summary,carbon quantum dots doped with different nitrogen sources and Fe3O4 modified with different electrical molecules were synthesized in this thesis and successfully used to construct the magnetic fluorescence dual-mode imaging platform.The proposal and implementation of this concept has potential applications in the biomedical field.