| Breast cancer leads the world in both incidence and mortality among women with cancer.Early diagnosis and early treatment can greatly improve the cure rate of breast cancer.The deficiencies of existing clinical detection methods have prompted researchers to find a new method for rapid,effective and sensitive detection of the molecular level biomarkers at the initial stage of breast cancer.Colorimetric biosensors have attracted wide attention from researchers because of their simple operation,rapid response,good reproducibility,low cost and other advantages.However,low sensitivity limits their applications.Signal amplification is often used to solve this problem.Bismuth selenide nanosheets(Bi2Se3)have high specific surface area,easy surface functionalization,high carrier mobility etc.As a typical topological insulator,Bi2Se3 has the unique properties of internal insulation and surface conductivity.Gold nanoparticles(AuNPs)have been widely used in biomedical fields due to their good biocompatibility,unique photoelectric properties and catalytic activity.Therefore,the combination of those two can produce Bi2Se3-AuNPs nanocomposites with superior properties.In this paper,Bi2Se3 and HAuCl4 were directly used to produce the Bi2Se3-AuNPs nanocomposites by in-situ growth of AuNPs on the surface of Bi2Se3 nanosheets.The nanocomposites were used as catalysts to fabrication of colorimetric biosensor for the detection of biomarkers of breast cancer,furthermore the signal amplification mechanism was discussed.The main results are as follows:1.Bi2Se3 was prepared from bismuth nitrate and sodium selenite by solvent thermal method.The Bi2Se3-AuNPs nanocomposites were prepared by ultrasonic reaction with HAuCl4,and AuNPs grew in-suit on Bi2Se3.2.The sulfhydryl modified capture probe and signal probe were respectively fixed on the gold-plated substrate and surface of nanocomposites by gold-sulfur bond.The sandwich structure was formed by the specific combination of the target-biomarker and the probe to connect Bi2Se3-AuNPs nanocomposites.The nanocomposites were used to catalyze the reduction reaction of 4-nitrophenol(4-NP).The color changed from yellow to colorless,which was used as a visual signal for the color reaction to construct a colorimetric biosensor.3.The biomarkers of breast cancer were detected by the colorimetric sensor and the kinetic constants of the catalytic reaction were positively correlated with the concentration of the target-substance.The limit of detection for the DNA fragments of breast cancer-related gene mutations can reach up to 10-18 M and there is a good linear relationship between the reaction kinetics constant and the DNA concentration to be tested at 10-12-10-18 M.The limit of detection for other breast cancer biomarkers such as miR-21,mRNA and MCF7 is 10-12 M,10 ng?L-1 and 1000 cells mL-1.The limit of detection for small molecule ATP can reach 10-7 M.All the above detections had good specificity.4.The signal amplification mechanism of the colorimetric sensor was studied.It can be found that AuNPs can amplify the detection signal by 102 times,graphene oxide-UuNPs further amplify the signal by 104 times,black phosphorus-AuNPs can amplify signal 107 times while Bi2Se3-AuNPs can amplify signal upto 1010 times.It was found that Se was oxidized by comparing before and after catalysis of the nanocomposites material,which proved that the electrons were lost in the reaction process.Illumination can promote the oxidation of bismuth selenide to remove electrons and improve the catalytic efficiency.However,the catalytic efficiency of Bi2Se3 coated with dopamine was decreased,indicating that the inhibition of electron transport would affect the signal amplification.Bi2Se3 acts as an electron donor and provides electrons for the catalytic reaction,thus improving the catalytic efficiency. |
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