The Preparation Of Rare Earth Upconversion Fluorescence Materials And Their Applications In Biodetection

Rare earth upconversion fluorescence nanoparticles?upconversion nanoparticles,UCNPs?are the important and high-profile luminescence materials in recent years.They can absorb two or more low-energy photons and converted them into a higher energy photon.Compared with traditional biomolecule fluorescent markers such as organic fluorescent dyes and quantum dots,upconversion fluorescence nanomaterials not only exhibit low toxicity,high luminescence intensity,good light stability,and large Stokes shift,but also can effectively avoid the autofluorescence interference in biological samples because the excitation light is infrared light,thereby reducing the detection background,enhancing biodetection sensitivity.Based on the above advantages,UCNPs have played a huge potential in the field of biological assays as novel biomarkers.So far,UCNPs have been applied to a wide range of biological assays,such as protein detection,nucleic acid detection,and have made great progress.However,the high sensitivity,high specificity,and well stable detection methods still require further research and development.In this paper,a new method has been developed for improving the accuracy and repeatability of biodetection based on the NaYF₄: Yb,Er UCNPs.The main research contents are as follows:1.The preparation and characterization of NaYF₄: Yb,Er UCNPs.We have explored the rare earth chlorides as raw materials,butanetetracarboxylic acid,citric acid salts,polyacrylic acid,oleic acid,and so on as the surface modifiers,and used hydrothermal method and thermal decomposition to prepare NaYF₄: Yb,Er UCNPs,respectively.Then,the particles sizes,morphologies,fluorescence intensity,and the surface-modified groups of the synthesized UCNPs were characterized by scanning electron microscopy,transmission electron microscopy,fluorescence spectroscopy,fourier transform infrared spectroscopy,and so on,respectively.Finally,the oleic acid coated NaYF₄: Yb,Er UCNPs were choosen for biodetection,which have uniform sizes?about 25 nm?,good monodispersity,uniform spherical,and high fluorescent properties.2.The surface modification and characterization of NaYF₄: Yb,Er UCNPs.The carboxyl bovine serum albumin?BSA?was used for UCNPs surface carboxyl modification.The carboxyl groups of UCNPs and the amino groups of probe were combined to prepare the UCNPs modified with DNA probes through amide reaction.By the analysis of transmission electron microscopy,fourier transform infrared spectroscopy,and fluorescence spectroscopy,a large number of carboxyl functional groups were successfully modified on the surface of NaYF₄: Yb,Er UCNPs by strongly covalently bind,and the particles have good water-solubility and high fluorescence intensity.3.The biodetection application of NaYF₄: Yb,Er UCNPs.According to the principle of base stacking force,we have ultilized NaYF₄: Yb,Er modified probe,target DNA or miRNA,report DNA to hybridize together,and used the fluorescence of NaYF₄: Yb,Er UCNPs as a reference standard to quantitatively detect target DNA or miRNA concentration for the first time.Lots of experimental results show that this method for the detection of DNA or miRNA has higher accuracy than no reference fluorescence,and can reduce the operation and equipments errors during the experiment.Moreover,the detection limit of this method reaches 5 nmol/L?DNA?or 10 nmol/L?miRNA?without reverse transcription and amplification,and also has a high specificity and repeatability.