Study Of Modular Magnetic Nanoprobe Construction And Tumor Theranostic Application

With the rapid development of nanotechnology,lots of nanomaterials have been applied in biomedical field,especially the emergence of some nanoprobes used in molecular imaging,which enables tumor diagnosis to achieve the better specificity and visualization.Magnetic nanoparticle is an important branch of nanomaterial and magnetic iron oxide(Fe₃O₄)nanoparticles have attracted widespread attention due to their inherent magnetic properties and good biocompatibility.In Magnetic Resonance Imaging(MRI)research,Fe₃O₄ nanoparticles can be used as contrast agents,which provide high sensitivity contrast enhancement effects.In general,most Fe₃O₄ nanoparticles are commonly used as negative(T2 enhanced)contrast agents.For ultrasmall sized Fe₃O₄ nanoparticles,due to their high r1 relaxation rate,it is expected to replace the Gadolinium agent to become a new generation of positive(T₁ enhanced)contrast agent.Therefore,it is significant to explore the preparation of Fe₃O₄ nanoparticles with T₁ enhanced magnetic resonance imaging and promote their further applications.Magnetic Fe₃O₄ nanoparticles can be used not only as a highly sensitive magnetic resonance contrast agent,but also as a carrier material for the construction of multifunctional intelligent nanoprobes.In the treatment of malignant cancer,compared with traditional drug treatment,tumor immunotherapy kills the tumor by activating the immune system,which effectively reduces the occurrence of toxic effect and drug resistant.Constructing an effective nanomaterials-based drug delivery system can enhance the immune killing effect in the tumor microenvironment and improve the effect of tumor immunotherapy.For the above aspects of the problem and based on the previous work,BSA modified ultra-small sized Fe₃O₄ nanoparticles were synthesized and they could be used as T₁-T2 dual-modal magnetic resonance imaging contrast agent in rabbit hepatic tumor.At the same time,the modular design of magnetic nanoprobe and their application in in vivo tumor imaging and therapy of non-Hodgkin lymphoma mouse model was presented,which further expanded the preparation and application methods of magnetic nanoprobes in this paper.The work of this paper is mainly divided into the following aspects:1.5 nm ultra-small superparamagnetic Fe₃O₄ nanoparticles(OAm@Fe₃O₄)coated with oleylamine molecules were prepared by high temperature thermal decomposition method.These nanoparticles had uniform particle size distribution,good dispersibility and high crystallinity.Then the bovine serum albumin(BSA)was coupled to the surface of nanoparticles to construct BSA@Fe₃O₄.BSA@Fe₃O₄ showed good magnetic properties with higher saturation magnetization(52.9 emu/g Fe)and relaxation rate(r1= 7.06 m M-1s-1).In vitro experiments it was proved that BSA @Fe₃O₄ had lower toxicity and good biocompatibility.In MRI of rabbit heaptic tumor,after injected with BSA@Fe₃O₄,due to the different method and number of nanoparticles taken by normal liver tissue and tumor tissue repectively,time-dependent T₁-T2 contrast effsct had been achieved.These dual-modal imaging improved the validation of tumor sites and provided new ideas for the application of such nanoparticles in MRI.2.The modular designed construction method of nanoprobe was proposed.The streptavidin was modified on the surface of Fe₃O₄ nanoparticles,and the biotin was modified on functional ligand.Then,due to the specific binding between biotin and streptavidin,the functional ligands were modified on the surface of the nanoparticles.The advantage of this method was that different ligands can be modularly combined to design nanoprobes with multiple functions.In the selection of different modules,CD3 monoclonal antibody which provides T cell activation,and CD20 monoclonal antibodies and E5 polypeptides which respectively capable of effectively targeting Raji cells and HL60 cells were used to construct the bispecific nanoprobes.These biospecific nanoprobes could target tumor cell and enhance immunotherapy at the same time.In vitro experiments,the constructed bispecific nanoprobes could effectively target and kill tumor cells.They could enhance the activity of T cells simultaneously,which increases killing effect of tumor cells.3.With a core size of 5 nm,CD20 and CD3 monoclonal antibody-modified bispecific modular magnetic nanoprobes were used in imaging and treatment of malignant lymphoma model mice.In magnetic resonance imaging and fluorescence imaging,the CD20 modified nanoprobes could effectively target tumor sites and exhibit better magnetic resonance-fluorescence dual-modal imaging.At the same time,in the treatment of tumor-bearing mice,after intravenous administration of humanized T cells and the nanoprobes,the tumor volume of the mice was significantly inhibited(the tumor suppression rate was 66.23%),and the survival time was effectively increased(from 39 day to 69 day),which proved that the nanoprobes have good therapeutic effect of malignant lymphoma.Thus,the bispecific nanoprobe can be used as theranostic nanoprobes in biomedical application.