Research On Carcinoembryonic Antigen Immunosensor Based On Gold-Vertical Graphene

Carcinoembryonic antigen(CEA)is a broad-spectrum tumor marker associated with a variety of cancers,including lung cancer,gastric cancer,and rectal cancer.The development of accurate,fast,and low-cost CEA immunosensors has important life significance in clinical applications such as cancer screening and diagnosis.A sandwich-type electrochemical immunosensor based on gold-vertical graphene(Au-VG)and Au@Si O₂-methylene blue(MB)was developed in this paper to detect the tumor marker CEA in human serum.The Au-VG working electrode is used to fix one antibody and the tested CEA,and the Au@Si O₂carrier is used to load the MB probe and the other antibody at the same time.First,a chemical vapor deposition(CVD)method was used to vertically grow a graphene film on a tantalum substrate,and a multi-potential step process was used to deposit gold nanoparticles on the graphene film in situ to construct an Au-VG working electrode.The combination of gold nanoparticles and vertical graphene makes the working electrode have good biocompatibility,large specific surface area,and high electrical conductivity,which enables it to immobilize a large number of coated antibodies and effectively amplify the response signal.Second,the photoreduction reaction was used to combine tetrachloroauric acid with amphiphilic Si O₂to form a Au@Si O₂carrier with a core-shell structure.The probe MB was modified onto the Au@Si O₂carrier to obtain Au@Si O₂-MB.In Au@Si O₂-MB,because the MB nanodots are smaller than 5 nm in size and have a high distribution density,high electrochemical signals can be generated.The nano-size effect of Au@Si O₂and the binding effect of Au,Si O₂(-OH)and antibody(-NH₂)enable Au@Si O₂-MB to fix antibodies in a large amount firmly.And a high labeling effect occurs between the antibody and the MB probe.Therefore,in this paper,the best experimental conditions for constructing a reliable and high-performance electrochemical immunosensor are studied in detail and a CEA quantitative detection model is constructed.Based on the same specificity of coating and detection antibody,a novel double-antibody sandwich strategy was developed to identify CEA in serum,further improving the sensitivity and stability of electrochemical sensors.Optimal parameters of CEA quantitative detection model were obtained through experiments of p H optimization,antibody concentration optimization,CEA incubation time optimization,MB concentration optimization,and regeneration effect optimization.The electrochemical immunosensor developed in this experiment has a linear detection range of 1 fg m L^-1to 100 ng m L^-1,sensitivity of0.045 m A(log(pg m L^-1))^-1),and detection limit of 0.8 fg m L^-1(S/N=3).In addition,the repeatability,specificity,stability,and reproducibility of immunosensors were evaluated.The recovery rate of CEA content in serum by using the immunosensor was99.3%to 100.1%,and the RSD was less than 6%,which verified the reliability and feasibility of the immunosensor in clinical application.