Abstract
We proposed a colorimetric immunosensor based on g-C3N4@Fe3O4 nanocomposite-mediated transformation strategy for sensitive detection of carcinoembryonic antigen (CEA). The g-C3N4@Fe3O4 nanocomposite was synthesized and characterized by the scanning electron microscope (SEM), energy dispersive X-ray spectra (EDX), X-ray powder diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR). Fe3+ derived from g-C3N4@Fe3O4 nanocomposite could combine with sodium salicylate to form purple complex products. Based on this color development, the sandwich colorimetric immunoassay was built by utilizing g-C3N4@Fe3O4 nanocomposite as nanolabels on the microplate. With the increasement of CEA concentration, the purple color showed a gradient change. Under optimal conditions, the linearity range is 0.001–50 ng/mL with the detection limit of 0.35 pg/mL for CEA. More importantly, the colorimetric immunoassay has good selectivity, specificity, repeatability, and stability.
Highlights
A key challenge for the development of colorimetric immunoassay is to transform the detection event into color change
G-C3N4@Fe3O4 generates a mass of Fe3+, which reacted with sodium salicylate and formed purple complex
After cooling to room temperature, the yellow g-C3N4 product was ground into powder for further use. en, 1 g of g-C3N4 powder was placed into a round-bottom flask with 100 mL of HNO3 (5 M), and backwash was performed for 24 h at 125°C
Summary
A key challenge for the development of colorimetric immunoassay is to transform the detection event into color change. G-C3N4@Fe3O4 nanocomposites were prepared as nanolabels to build colorimetric immunoassay for CEA detection. G-C3N4@Fe3O4 generates a mass of Fe3+, which reacted with sodium salicylate and formed purple complex. Based on this colorimetric phenomenon, CEA concentration in the serum is analyzed by semiquantitative analysis by naked eye and quantitatively analyzed by UV-vis absorption.
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