Rare Earth Upconversion Luminescent Nanomaterials Based On Energy Transfer For Biomolecular Fluorescence Detection And Biological Imaging

Nano-fluorescent materials have a wide range of applications in biomolecule fluorescence detection and imaging,among which rare earth ion-doped upconversion luminescent materials have a wide range of applications,such as large Stokes shift,high light stability,long fluorescence lifetime,good biological penetration and so on.In this thesis,rare earth nanoparticles with core-shell structure were prepared,and then two kinds of composite materials UCNP-PEG-NOF1 and UCNP@PEG@NDP were prepared by combining specific recognition probe with rare earth upconversion luminescence nanomaterials.Cysteine and hypochlorite upconversion luminescence detection and imaging were realized by energy transfer mechanism.The main research contents are as follows:Firstly,rare earth nanoparticles（UCNP:Na YF₄:20%Yb,2%Er@Na YF₄）with core-shell bilayer structure were prepared by thermal decomposition method.The amphiphilic polymer bisstearyl phosphatidylethanolamine-polyethylene glycol amine(DSPE-PEG₂₀₀₀-NH₂)was combined with oleic acid ligands on the surface of UCNP by hydrophobic interaction to form phospholipid-coated UCNP-PEG water-dispersible nanoparticles.Furthermore,the fluorescent probe NOF1 was assembled through the hydrophobic layer to form rare earth nanocomposite UCNP-PEG-NOF1.Based on the energy transfer mechanism,the rare earth upconversion nanocomposite UCNP-PEG-NOF1 could detect cysteine through the change of upconversion luminescence intensity.The structure of NOF1 was verified by NMR and high resolution mass spectrometry.The preparation of UCNP-PEG-NOF1 was proved by UV absorption spectra,upconversion luminescence spectra and Zeta potential measurements.The results of UV-absorption and upconversion luminescence spectra showed that UCNP-PEG-NOF1 had high sensitivity and selectivity for the detection of cysteine,and the detection limit was 83 n M.In addition,UCNP-PEG-NOF1 had good biocompatibility and had been successfully applied to cysteine upconversion fluorescence detection and imaging in vivo.Finally,UCNP-PEG was used for fluorescence imaging of schistosoma cercariae.The results of this study provided a certain experimental exploration for the use of rare earth up-conversion luminescent nanomaterials for fluorescence labeling of schistosoma cercariae.Secondly,phospholipid DSPE-PEG₂₀₀₀-NH₂ coated UCNP@PEG nanoparticles were prepared,and the hypochlorite recognition probe NDP was assembled to form rare earth nanocomposite UCNP@PEG@NDP.The developed UCNP@PEG@NDP can detect hypochlorite by upconversion luminescence intensity change.The structure of NDP was verified by NMR and high resolution mass spectrometry,and the detection properties of hypochlorite for NDP were tested by UV-absorption and fluorescence spectra.Furthermore,the experimental results of UV-absorption spectra and upconversion luminescence spectra showed that UCNP@PEG@NDP can detect hypochlorite and had high sensitivity and selectivity to hypochlorite,and the detection limit was 86 n M.More importantly,UCNP@PEG@NDP had been successfully applied to HCl O detection and fluorescence imaging in live cells and organisms,and could be used for hypochlorite fluorescence imaging of mouse arthritis model.