Preparation Of Mri-nirf Dual Mode Image Nanoprobe

Medical imaging technology plays an important role in tumor diagnosis,and combine magnetic resonance imaging technology with in vivo near-infrared fluorescence imaging technology can get better imaging results.In this paper,we chemically coupled Cy7 dye(Cyanine 7)on the surface of ultra-small superparamagnetic iron oxide(USPIO)which has the Ti-weighted MRI enhancement effect,and finally prepared a passive target tumor MRI-NIRF dual mode nanoprobe.This nanoprobe achieves passive targeting tumor and dual modal image enhance in mice with subcutaneous breast cancer.In this paper,the USPIO nanoparticles were prepared by high temperature pyrolysis method,and the PEG was modified on it by surface substitution method.The magnetic core size of PEGized magnetic nanoparticles was about 4.4 nm and the hydrodynamic size was about 15 nm.The surface of the PEGized nanoprobe has a negative charge(Zeta potential is about-15.4 mV)due to the terminal PEG carboxyl group;the magnetic core has a cubic spinel structure and superparamagnetic,and the saturation magnetization is about 64 emu/g Fe.Then,the EDC/NHS chemical coupling method was used to couple the Cy7 amine with the PEG terminal carboxyl groups on the surface of the nanoparticles to obtain a MRI-NIRF dual mode nanoprobe with similar super paramagnetism.Due to the modification of Cy7,the hydrodynamic size and Zeta potential respectively changed to about 16 nm and-3.7 mV.Fluorescence spectra and magnetic resonance relaxation measurements show that the dual mode nanoprobe had excellent fluorescence properties and high relaxation rate(r1= 10.6 mM-1 s-1).In the end,the animal experiments of tumor-bearing mice further confirmed that the dual-mode nanoprobe could be targeted to the tumor site,and the T1-weighted MRI and NIRF imaging of the tumor site were enhanced.The tumor site MRI signals and NIRF signals are changed similar,after tail vein injection the both of them rapidly enhanced,then within 8 hours after injection maintain a high level,with a long time sight window.Due to the high tissue interstitial pressure in the tumor,the fluorescence imaging signal of the passive target nanoprobe was significantly reduced 24 hours after the injection,but the contrast of fluorescence intensity of the tumor was still very strong due to the faster reduction of the background signal of the normal tissue.