Construction And Characterization Of MR Molecular Probe USPIO-PEG-sLe~x Targeted Endothelial Cell Adhesion Molecule-1 And Imaging Study In Vivo And Vitro

Objectives: 1.To investigate the methods of preparing a specific molecular probe for magnetic resonance imaging targeting endothelial cell adhesion molecule-1(ELAM-1)with ultrasmall superparamagnetic particles of iron oxide(USPIO)chelating sialyl-Lewis x(s Lex),and research its physicochemical properties.2.Nude mice were used to form Nasopharyngeal Carcinoma xenografts models.Use USPIO conjugated sialylase x(s Lex)to form a specific magnetic molecular probe(USPIO-PEG-s Lex)targeting endothelial cell adhesion molecule-1(ELAM-1),and explore the value of the molecular probe in nude mice model of nasopharyngeal carcinoma xenograft.Methods: Using physical deposition method to synthesis USPIO nanoparticles.By hydrophobic interactions,preferable water-soluble PEG-SPIO was synthesized and the surface-COOH was sufficiently activated,then incubated with sufficient s Lex at room temperature,purified by centrifugal ultrafiltration and washed with deionized water.Then the magnetic resonance molecular probe USPIO-PEG-s Lex was prepared.The morphology and particle sizes were observed with transmission electron microscope(TEM),and the average hydrodynamic size was detected by dynamic light scattering(DLS)before and after coupling.The Zeta potential of USPIO-PEG-s Lex was detected by particle size analyzer before and after coupling.The 10 nude mice model of nasopharyngeal carcinoma xenograft were randomly divided into experimental groups and control groups.USPIO-PEG-s Lex and USPIO-PEG was injected into nude mice of experimental groups and control groups by caudal vein,respectively.MR T2 mapping imaging was scanned before and after the injection,which aimed at analyzing the changes of T2 values between experimental and control groups.After scanning MR T2 mapping imaging,immunohistochemical SP method was used to analyze the expression of ELAM-1 in new vascular endothelial in xenograft.Results: TEM results revealed that the PEG-SPIO had a size of(10 ± 2.6 nm)with good dispersibility and suitable size.DLS study showed that before and after coupling,the hydrodynamic mean diameter were(34.06 ± 9.95)nm and(53.35 ± 16.99)nm,respectively;Zeta potential study showed that before and after coupling the potential of PEG conjugated magnetic nanoparticles potential were(11.6 ± 3.96)m V and(-12.6 ± 5.33)m V,respectively.USPIO-PEG-s Lex had a good representation.The difference of unenhanced tumor T2 values between control group and experimental group had no statistical significant(P>0.05).However,the difference of T2 values between two groups after injections was statistically significant(P<0.05),and the experimental group's T2 values were much lower than the control group's T2 values.The difference of enhanced rate between the two groups was statistically significant(P<0.05).The results of immunohistochemistry showed that E-selectin was expressed in the cytoplasm or membrane of vascular endothelial cells.HE staining showed that the nucleus was dark blue,showing obvious atypia,cytoplasm and fibrous tissue were stained ranging from light red to dark red.Conclusion: The method of chemical conjugation can be successfully prepared MRI molecular probe USPIO-PEG-s Lex,which has a well-characterized molecular probe,and it is expected to meet vivo experiments specifically binds to ELAM-1 requirements.USPIO-PEG-s Lex magnetic nanoparticles may expect to be used as a targeted contrast agent to ELAM-1 expression of nasopharyngeal carcinoma,indicating that USPIO-PEG-s Lex have good potential prospects.