Novel rapid coordination of ascorbic acid 2-phosphate and iron(III) as chromogenic substrate system based on FeO nanoparticle and application in immunoassay for the colorimetric detection of carcinoembryonic antigen.

This work for the first time reports on a simple and rapid colorimetric immunoassay with rapid coordination of ascorbic acid 2-phosphate (AAP) and iron (III) for determination of carcinoembryonic antigen (CEA, used as a model) by using FeO nanoparticle based-chromogenic substrate system. The signal was produced rapidly (1 min) from the coordination of AAP and iron (III) with color development of colorless to brown. TD-DFT calculation methods were employed to simulate the UV-Vis spectra of AAP-Fe and AAP-Fe complexes. Moreover, FeO nanoparticle could be dissolved with the aid of acid, thereby releasing free iron (III). Herein, a sandwich-type immunoassay was established based on FeO nanoparticle as labels. As target CEA concentration increased, the number of FeO labelled-antibodies (bound specifically) increased, resulting in loading more FeO nanoparticle on platform. The absorbance increased as the number of free iron (III), derived from FeO nanoparticle, increased. So, the absorbance of reaction solution is positively correlated with antigen concentration. Under optimal conditions, the current results showed good performance for CEA detection in the range 0.02-10.0 ng/mL with a detection limit of 11 pg/mL. Moreover, the repeatability, stability, and selectivity of the colorimetric immunoassay were also acceptable.