Detection Of Carcinoembryonic Antigen （CEA） By Near Infrared Nanoparticles NaYF₄:Yb,Nd@CaF₂

Colorectal cancer is one of the most common cancers of the digestive tract.With the improvement of people’s living standards,the intake of high-fat food and lack of physical exercise and other factors that induce colorectal cancer increase,leading to the increasing incidence and mortality rate.In view of this situation,we should not only strengthen the health education of cancer prevention,but also increase the strength of advance screening,so as to gain time for the early treatment of cancer.Therefore,it is particularly important to develop a rapid and convenient method for the detection of colorectal cancer.NIR rare earth luminescent materials can effectively exclude the interference of visible light and colored samples because the wavelength of excitation light and emission light are in the NIR region,and the luminescent intensity can be tuned according to the doping ratio of rare earth ions,so it has great development potential in the field of immune detection.In this study,the near-infrared down-converted nanocrystalline NaYF₄:Yb,Nd@CaF₂ was combined with immunochromatography to establish a highly sensitive and anti-interference fluorescence immunoassay platform,which can realize the clinical real-time and rapid detection of carcinoembryonic antigen（CEA）,a common marker of colorectal cancer.Firstly,in order to obtain a biocompatible fluorescent probe of nanocrystals with high luminescence,the influencing factors of the luminescence properties of nanocrystals were explored in this study,and ligand modification was carried out on the surface of the nanocrystals.The results show that the fluorescence intensity of mononuclear NaYF₄:Yb,Nd nanocrystals coated with Ca F₂ shells increases by about64 times.The doping ratio of rare earth ions in nanocrystals was further investigated.When the doping ratio of Nd³⁺ions was 30%,the luminescence intensity of both single core and core-shell structure was the strongest.In addition,hydrophilic ligand polyacrylic acid（PAA）was modified on the surface of NaYF₄:10%Yb,30%Nd@Ca F₂nanocystalline,which laid a foundation for the further application of fluorescent probe in biology.Secondly,an optimized Near-Infrared down-conversion Nay F₄:Yb,Nd@Ca F₂nanometer fluorescent probe was used to establish the immunoassay platform for flow measurement,and CEA was detected after the detection environment was regulated.The results show that the linear concentration range of the detection platform established in this project is 0.5-10 ng/m L,and the linear regression equation is as follows:T/C=0.32869+0.06889×c（CEA）（R²=0.998）,and the limit of detection（LOD）was 0.5 ng/m L.The specificity test showed that the specificity of the method was good,and the accuracy of the detection was within an acceptable range.The normal concentration of CEA in human body for clinical medical detection is below 4 ng/m L.The detection platform prepared in this project includes the concentration in the detectable linear range,so clinical instant medical detection can be realized.Sensitive immunochromatographic dipstrips allow medical personnel to quickly diagnose patients in the early stages of colorectal cancer and select appropriate treatment options as soon as possible.