| Carcinoembryonic antigen(CEA)is one of the most frequently studied tumor markers,which is associated with many types of cancer.CEA is a cell surface glycoprotein with a molecular weight of about 200 k Da,which participates in cell adhesion and plays a part in cell recognition and interaction.It is considered as a reliable broad-spectrum tumor marker.The determination of tumor markers plays a vital role in tumor screening,diagnosis and prognosis evaluation.Among the many detection methods,the colorimetric immunoassay method has attracted much attention due to its low cost,easy operation and visual detection.Nanomaterials have a wide applications in immunoassays due to their excellent physical and chemical properties.Among them,two-dimensional nanomaterials have the advantages of large specific surface area,multiple active binding sites,excellent thermal stability and chemical stability,which make it play an important role in colorimetric immunoassay.In this study,g-C3N4/Ce O2,g-C3N4/Cu O,g-C3N4/Fe3O4composite nanomaterials were prepared,and colorimetric immunoassay methods were constructed based on those nanomaterials as labels for quantitative detection of CEA.The main research content and results are as follows:(1)The g-C3N4/CeO2composite nano material was prepared by hydrothermal method based on g-C3N4 and cerium nitrate.Under visible light irradiation,the g-C3N4/Ce O2materials undergo electronic transitions and form photo-generated holes(h+).h+can catalyze the oxidation of TMB into blue oxide TMB(TMBOX).Based on this principle,using g-C3N4/Ce O2as nanolabels,a visible light-excited colorimetric immunoassay method was constructed to detect CEA.Under optimal conditions,there was a linear relation between absorbance and target protein concentration in the range of 0.5 ng/m L–8.0 ng/m L with the detection limit of 20 pg/m L.(2)The g-C3N4/CuO composite material was prepared by calcineing of melamine and copper nitrate at high temperature,and the antibody was cross-linked on the surface of the composite material through chitosan(CS)to construct a sandwich immunoassay system.Due to the excellent photocatalytic properties of g-C3N4/Cu O composite nanomaterials,it catalyzes the oxidation of TMB to form blue oxide TMB(TMBOX).Under optimal conditions,the absorbance of the colorimetric immunoassay was linearly correlated with the CEA concentration in the range of 0.001-20 ng/m L,and the lowest detection limit was 0.001ng/m L.The immunosensor has a wider detection range and a lower detection limit.(3)The g-C3N4/Fe3O4composite was prepared by the hydrothermal method in ethylene glycol soultion.A sandwich colorimetric immunoassay in a 96-well plate was constructed by using g-C3N4/Fe3O4as labels for detection of CEA.Under concentrated acid conditions,g-C3N4/Fe3O4was decomposed to form Fe3+,and Fe3+reacts with sodium salicylate to form a purple complex.Under the optimal conditions,the absorbance of the color-developing system has a good linear relationship with the concentration of CEA in the range of 0.001 ng/m L to50 ng/m L,and the limit of detection(LOD)is 0.001 ng/m L.Meanwhile,the colorimetric sensor has good stability,specificity and anti-interference. |
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