The Synthesis Of Fluorescence/Magnetic Resonance Imaging Dual Functional Materials Based On CdTe Quantum Dots

Because single imaging technology has its own advantages and disadvantages in imaging depth,spatial-temporal resolution and sensitivity,the combined use of multiple imaging technologies,that is,the integration of multiple imaging diagnostic modes to achieve complementary advantages,can obtain more real,accurate and comprehensive diagnostic results.In recent years,with the development of medical science,multi-modal fusion technology has widely studied in the field of biomedical imaging.At the same time,dual-mode optical imaging materials with fluorescence/magnetic resonance imaging function have excellent optical imaging performance,superparamagnetism,biocompatibility and effective drug loading,which greatly improve the sensitivity and accuracy of detection,can be used in cell marking and separation,drug targeting delivery,cancer diagnosis and treatment and so on.Most of magnetic center materials reported are superparamagnetic nanoparticles,such as Fe₃O₄,Fe₂O₃ and gadolinium compounds.Because magnetic materials?Fe₃O₄?are easy to agglomerate and have poor corrosion resistance,difficult to wash and could quench fluorescence emission of luminescent particles,and fluorescence intensity of luminescent particles will decrease obviously,which limits its further application.The 4f layer of Gd³⁺with seven unpaired electrons has strong paramagnetism,which could not cause obvious quenching of fluorescence emission intensity of luminescent particles,therefore gadolinium compounds have been widely used in magnetic resonance imaging?MRI?.In particular,gadolinium oxide?Gd₂O₃?modified with polyacrylic acid,D-glucuronic acid and bovine serum albumin have been used in MRI image diagnosis of cancer.However,studies found that gadolinium-based contrast agents had the risk of inducing renal fibrosis,in order to improve the clinical safety of contrast agent,Mn²⁺has been used to replace Gd³⁺.At present,MnCl₂?LumenHance??and[Mn-DPDP]^4-?Teslascan??have been used in clinical diagnosis for enterography and hepatography.However,free Mn²⁺may be hazardous to the human body,in recent years,manganese oxides?MnO and Mn₃O₄?have been widely studied as a T₁ contrast material.In this paper,zero-valent iron,gadolinium fluoride and manganese tetroxide have been used as magnetic resonance imaging materials,CdTe quantum dots have been used as fluorescence imaging materials,and both two materials have been compounded into silica microspheres to form stable spherical or vesicle structures,and multimodal optical imaging materials with good magnetic resonance,fluorescence tracer and drug-loading properties have been successfully prepared.A zero-valent iron amorphous calcium phosphate composite?Fe⁰/ACP composites?,Fe⁰/ACP/CdTe quantum dots microspheres,CdTe@SiO₂@GdF₃ microspheres,CdTe/Mn₃O₄/SiO₂ microspheres fluorescence/magnetic resonance imaging dual functional microsphere with core/shell structure have been successfully synthesized,and of which structure,magnetic resonance imaging and fluorescence property were characterized by EDXA,TEM,MRI and fluorescence spectra.SEM and TEM analysis showed that the particle size of Fe⁰/ACP microspheres was about 300 nm,and hysteresis loops indicated that Fe⁰/ACP microspheres could be separated from the nonmagnetic materials in a magnetic field.Nitrogen adsorption-desorption isotherm showed that the Fe⁰/ACP microspheres have adsorption capacity and could absorb CdTe quantum dots,of which absorption process has been analyzed by the pseudo-second-order rate equation.The XRD,FTIR,fluorescence spectrum and hysteresis loops were also used to characterize this absorption product Fe⁰/ACP/CdTe quantum dots microspheres,results indicated that these adsorption products Fe⁰/ACP/CdTe quantum dots microspheres not only maintained the magnetic properties,but also exhibited good fluorescence emission ability.TEM images indicate that as-prepared CdTe@SiO₂@GdF₃microspheres have obvious spherical core/shell structure,and a large number of GdF₃dispersed well on the surface of silica in the form of small particles with the particle size of5-8 nm.EDXA analysis indicates that there are Si,O and Gd elements on the surface of CdTe@SiO₂@GdF₃ microspheres,and Gd has successfully doted in the CdTe@SiO₂composite.Fluorescence spectra of CdTe@SiO₂@GdF₃ microspheres indicated that these microspheres had good fluorescence property with a red shift of fluorescence emission wavelength.Basis on the slope of magnetic resonance imaging analysis,the value of r₁ at 3 T magnetic strength of 3.48 s^-1?mm?^-1could be obtained,indicated that as prepared CdTe@SiO₂@GdF₃ microspheres could be applied on magnetic resonance imaging.The cytotoxicity experiment of CdTe@SiO₂@GdF₃ microspheres shown that the cell viability could reach above 90%,when concentration of as prepared CdTe@SiO₂@GdF₃ microspheres reached 200?g/mL,indicated that the toxicity on cells was weak.TEM images indicated that as-prepared CdTe/Mn₃O₄/SiO₂ composites had obvious spherical core/shell structure,EDXA analysis indicated that there were Si,O and Gd elements on the surface of CdTe/Mn₃O₄/SiO₂microspheres,all these results indicated that CdTe quantum dots and Mn₃O₄ nanocubes had been successfully encapsulated in silica microspheres.Fluorescence spectra indicated that CdTe/Mn₃O₄/SiO₂ microspheres had good fluorescence property with a blue shift of fluorescence emission wavelength.Basis on the slope of magnetic resonance imaging analysis,the value of r₁ at 3 T magnetic strength 3.88 s^-1?mm?^-1 could be obtained,indicated that as prepared CdTe/Mn₃O₄/SiO₂ microspheres could be applied on magnetic resonance imaging.The cytotoxicity experiment showed that the cell viability could reach above 90%,when concentration of as prepared material was 300?g/mL,indicated that The cytotoxicity experiment of CdTe/Mn₃O₄/SiO₂ microspheres shown that the cell viability could reach above90%,when concentration of as prepared CdTe/Mn₃O₄/SiO₂ microspheres 300?g/mL,indicated that the toxicity on cells was weak.The fluorescence/magnetic resonance imaging bifunctional microspheres we have synthesized could be used in fluorescence detection and biological detection.