Synthesis And A Preliminary In Vivo Study Of Tf-SPION:as A MR Molecular Probe For Transferrin Receptor

Part Ⅰ:Preparation and characterization of the magnetic resonance molecular imaging probes:transferrin (Tf)-superparamagnetic iron oxide nanoparticles (SPION)Objective:To synthesis the MR molecular imaging probes Tf-SPION and characterize the physicochemical properties of the prepared probes.Materials and Methods:Tf-SPION is synthesized according to the principle of the amidation reaction. The carboxyl groups in the surface of SPION are actived by the activating agent1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDAC) and protective agent N-hydroxy succinimide (NHS). The actived SPION particles are separated as the form of precipitation with a magnetic plate. The precipitation is washed with phosphate buffer solution (PBS) to remove the unreacted EDC and NHS. Then the precipitation is dispersed in the PBS. Transferrin is added into the actived SPION solution and reactived overnight at room temperature. Adsorb the precipitation with a magnetic plate, and remove the supernatant. The concentration of Tf-SPION is adjusted to5mg/ml with PBS.The infrared spectroscopy is used to identify the compounds of the synthesized precipitation which is a single component of Tf-SPION but not a mixture. The surface morphology is detected by the transmission electron microscopy (TEM) and dynamic light scattering (DLS). Then the T2relaxation rate is tested respectively by MR.Results:The MR molecular imaging probes Tf-SPION is synthesized successfully with the amidation reaction method.The precipitation is conformed to be the single compound of Tf-SPION but not the mixture of the Tf and SPION by infrared spectroscopy. Tf-SPION particles are spherical and uniform in the image of TEM and DLS, with a particle mean size is18.3±1.1nm,143.5±49.36nm respectively, and the SPION is7.9±0.5nm,71.45±29.80nm respectively. The Tf-SPION relaxation rate is94.618mM/s and the SPION relaxation rate is173.39mM/s.Conclusion:The chelate Tf-SPION we have synthesized shows the conditions for MR molecular image probes and can be used for MR molecular imaging. Part Ⅱ:In vivo study of Tf-SPION for MR molecular imaging in a rat liver cancer modelObjective:To investigate the characteristic of Tf-SPION for molecular imaging in a rat hepatic tumor model via artery or vein route. Materials and methods:Fourty Spraque-Dawley(SD) rats implanted with Walker-256tumors in the hepatic left lateral lobes were randomly divided into five groups (A, B, C, D and E) with8rats each. Retrograde gastroduodenal arterial catheterization with polyethylene microcatheter was performed under the surgical microscope in the group D and E.0.2ml Tf-SPION and0.2ml SPION was injected into hepatic artery in the group D and group E respectively.0.2ml saline,0.2ml SPION and0.2ml Tf-SPION was injected into tail vein in the group A, B and group C respectively. Abdominal MRI was performed at1hour,4hours,1day and4days after the injection of Tf-SPION or SPIO in each group. T2signal intensity of the tumor and the back muscle tissue was measured in the maximum tumor diameter section, and the relative signal intensity ratio(RR) was calculated. Four rats were sacrified at1hour and4days after MRI in each group, iron particles in the liver were tested by Prussian blue staining.Results:The rat liver cancer model was established successfully. There was no significant difference of RR between group A and group B (P<0.01). And there was significant difference of RR between group C and group B (P<0.01) at each timepoint after intervention, and the same difference between group D and group C(P<0.01). The statistics difference was found between group D and group E at the first timepoint (P<0.01). Group D showed the most efficient hepatic tumor uptake of iron particles compared with other groups by Prussian blue staining. Conclusion:The results suggested Tf-SPION as a potential MR imaging probe for cell tracking. Introduction of Tf-SPION via artery may be used as a new novel method for the diagnosis evaluation of hepatic tumor.