Construction Of Quantum Dot Fluorescent Aptamer Sensor And Its Application In Detecting Tumor Markers

Tumor biomarkers are a substance produced with changes in cellular genes.They are an important indicator for early detection,diagnosis,treatment,and prognosis evaluation of cancer,and have broad clinical application prospects.However,the content of tumor markers in body fluids is often low,and effective detection of tumor markers has always been an important research topic in the fields of biology and medicine.In recent years,fluorescent aptamer sensors using quantum dots labeled aptamers（QDs-Apt）as molecular recognition elements and fluorescent donors,as well as layered nanomaterials as receptors,have provided effective methods for detecting tumor biomarkers with a wide range and low detection limit.This article focuses on the tumor marker mucin 1（MUC1）as the detection object.Based on the principle of fluorescence resonance energy transfer（FRET）,two fluorescent aptamer sensors,g-CNQDs Apt/WS₂ and g-CNQDs-Apt/WS₂/Fe₃O₄,were constructed.The experimental conditions were optimized to achieve quantitative detection of serum MUC1,and the role of magnetic separation in improving the performance of the sensor in detecting MUC1 was clarified.The main content of the paper is as follows:（1）g-CNQDs-Apt/WS₂ fluorescent aptasensor for detecting MUC1.Graphite carbon nitride quantum dots（g-CNQDs）with blue fluorescence were prepared by thermal polymerization.After covalently linking Apt with amide bonds,the obtained g-CNQDs-Apt served as MUC1 molecular recognition elements and energy donors;The WS₂ nanosheets obtained by hydrothermal synthesis method serve as energy receptors,and the fluorescence intensity of g-CNQDs can be effectively quenched by adsorption of Apt,resulting in FRET between the two.When MUC1 is present in the system,Apt specifically recognizes and binds to it,causing g-CNQDs-Apt to detach from the surface of WS₂ nanosheets and restore the fluorescence intensity of the system.At a concentration of 10～80 ng/m L,there is a good linear correlation between the logarithmic concentration of MUC1 and the fluorescence relative recovery rate of the g-CNQDs-Apt/WS₂ system（R²=0.99068）,with a limit of detection（LOD）1.01 ng/m L,an RSD of 2.2～3.8%,and a recovery rate of 94.89～103.2%.（2）g-CNQDs-Apt/WS₂/Fe₃O₄ magnetic separation fluorescence aptasensor for detecting MUC1.In order to further improve the performance of fluorescence aptamer sensors for detecting MUC1,based on g-CNQDs-Apt/WS₂/Fe₃O₄ nanoparticles were loaded onto WS₂nanosheets,and magnetic separation was used to reduce the fluorescence background of the supernatant in the system,thereby improving the sensor performance.The experimental results indicate that MUC1 binds specifically to g-CNQDs-Apt,which directly leads to its adsorption on the surface of WS₂/Fe₃O₄ nanocomposites.After magnetic separation,the relative recovery rate of fluorescence in the system increases significantly.At 10～100ng/m L,the logarithmic concentration of MUC1 still maintained a good linear correlation with the fluorescence relative recovery rate of g-CNQDs-Apt/WS₂/Fe₃O₄ system（R²=0.99256）,with a LOD of 0.89 ng/m L,an RSD of 3.24～4.68%,and a recovery rate of94.99～112.39%.It can be seen that magnetic separation effectively reduces the fluorescence background of the g-CNQDs-Apt/WS₂ sensing system and improves the linear range performance of MUC1 detection.The research results have important reference value for the construction of fluorescent aptamer sensors for other tumor markers and even other targets,and have broad application prospects in the fields of biology and medicine.