Upconversion,Time-gated,Nuclear Magnetic Resonance Multimode Imaging Fluorescence Probe:Synthesis And Application

Fluorescence imaging technology is a kind of non-invasive imaging,which has high sensitivity and accuracy for invivo imaging.Therefore,fluorescence imaging has been widely used in biological and medical fields.Many fluorescent materials,such as organic fluorescent dyes,quantum dots and metal complexes,have been successfully used in fluorescence imaging.Upconversion materials have the advantages such as good chemical stability,strong tissue penetration and low cytotoxicity,therefore more and more upconversion materials are used in the biological imaging,cell marking,drug delivery,magnetic imaging and so on.Time-gated fluorescence is a kind of technology which using Eu³⁺,Tb³⁺,Sm³⁺as organic ligands to form chelates with long fluorescence lifetime,which can eliminate the interference of the short fluorescence lifetime of background fluorescence.Therefore,time-gated fluorescence imaging has the advantages such as high sensitivity,long fluorescence lifetime,low background fluorescence.In addition,nuclear magnetic resonance imaging is a common imaging method in the medical field.Nuclear magnetic contrast agents can improve the contrast and resolution of nuclear magnetic imaging.Most commonly used contrast agents are synthetic materials doped with Gd3+and magnetic iron oxide.Combining the advantages of three kinds of imaging,in this work we develop a multi-mode nanoscale fluorescence probe which can simultaneously have upconversion,time-gated and nuclear magnetic.According to the advantages of the three kinds of imagings,we designed and prepared a multi-mode imaging nanofluorescent probe including the following aspects:Firstly,the upconversion nanoparticles NaYF₄:Yb³⁺/Nd³⁺/Ho³⁺were synthesized by hydrothermal method.The results of scanning electron microscope show that the particle size were larger than 100 nm.Therefore,upconversion nanoparticles NaYF₄:Yb³⁺/Nd³⁺/Ho³⁺is not conducive to the application of biological imaging.The upconversion nanocrystalline NaGdF₄:Yb³⁺/Nd³⁺/Ho³⁺were prepared which has uniform dispersion and the particle size were less than 50 nm.The photoluminescence properties of the upconversion nanoparticle were characterized.The luminescence properties were optimized by adjusting the proportion of doped ions.Finally,it was found that when the doping ratios of Yb³⁺,Nd³⁺,and Ho³⁺were7.5%,4%,and 1%,respectively,the luminous efficiency of the upconversion nanoparticles was the best.Then,using the inverse microemulsion method:Igepal CO-520 was used as the surfactant,tetraethylorthosilicate?TEOS?was used as the silanization reagent,ammonia was used as the initiator to perform the polymerization reaction,and the upconversion nanoparticles NaYF₄:Yb³⁺/Nd³⁺/Ho³⁺were coated with the APTES-BHHBCB-Eu³⁺precursor to form core-shell nanoparticles?TUM-NPs?with amino groups on the surface,and its morphology and optical properties were characterized.The results showed that TUM-NPs have good conversion and luminescence properties,which can perform time-resolved fluorescence measurement and have uniform particle dispersion with an average particle size of less than 50 nm.Finally,TUM-NPs were covalently bonded with folate Folic acid?FA?which were used for time-gated and upconversion flourescence imaging of HeLa.The results of upconversion and time-gated fluorescence recognition imaging using TUM-NPs-FA as luminescent biological fluorescent probe was confirmed that in identification of the folate receptors on the surface of cancer cells was feasible.The NMR relaxation of TUM-NPs-FA was performed to demonstrate the magnetic properties of the TUM-NPs-FA,which can further apply to MRI in all probability...