Accurate Tumor Imaging Of Functionalized Magnetic Nanodots

Magnetic nanomaterials(MNMs)have been widely studied in recent years because of their potential applications in biomedicine and catalysis.In biomedicine,MNMs can be used in magnetic resonance imaging,photothermal therapy,imaging guided therapy,etc.Among them,Magnetic resonance imaging(MRI)technology is one of the main clinical diagnostic methods in current medical practice.It has the advantages of non-invasive,high spatial resolution,high soft tissue contrast,etc.And the application of contrast agents has expanded the clinical application range of MRI,and has a very important value in the detection,qualitative and efficacy evaluation of lesions.Currently,the main contrast agent used to enhance longitudinal relaxation rate(r1)is paramagnetic gadolinium(Gd)-based chelating agent.However,gadolinium is not an essential element in humans,and due to its poor stability,uncontrolled pharmacokinetics,and toxicity,the U.S.Food and Drug Administration(FDA)has warned that gadolinium chelating is associated with renal systemic fibrosis(NSF),leading to impaired renal function.Therefore,it is still an urgent need to develop high sensitivity and high stability metal-based magnetic resonance contrast agents which are better than existing contrast agents.In addition to magnetic properties,some MNMs have enzyme-like activity due to their highly specific chemical composition and surface structure,which can overcome the shortcomings of natural enzymes such as high cost of preparation and purification,poor stability,sensitive catalytic conditions,etc.Therefore,it is of great significance to develop nanozymes with high stability and catalytic activity.In the second chapter,we prepared Fe-coordinated carbon dots(Fe-CDS)using food additives and amino acids as precursors to achieve T2 magnetic resonance imaging of tumors,based on that Fe(Ⅲ)can coordinate with weak-field ligands,resulting in high spin d5 complexes having the properties of Gd(Ⅲ)preparations.In addition,we found that it has peroxidase-like activity,due to the doping of Fe(Ⅲ).It can be used as a new nanozyme to realize the quantitative detection of glucose and ascorbic acid.In the third chapter,we further prepared carbonized paramagnetic complexes of manganese(II)(Mn@CCs),with ultra-high ri relaxation rate(22.1 mM-1s-1,9.4 T),and higher security and studies have shown that Mn@CCs could penetrate normal blood brain barrier(BBB),can be used for in situ super cerebellum glioma and multinodular orthotopic liver tumor magnetic resonance imaging.More importantly,Mn@CCs is effectively excreted from the host by renal clearance 4 hours after injection.The high tumor-normal ratio provided by Mn@CCs provides new opportunities for early molecular diagnosis and imaging guided biomedical applications.We provides new insights to study magnetic resonance contrast agents,and a new peroxidase was developed that brings bright prospects for diseases diagnosis.