A Colorimetric Immunoassay Based on Coordination Polymer Composite for the Detection of Carcinoembryonic Antigen

Coordination polymers (CPs) as fascinating materials have been explored in a number of fields due to their diverse properties. In this work, we demonstrate the feasibility of CPs in the facile fabrication of multifunctional composites for establishing an immunoassay. To this end, a zinc(II)-based CP (ZnCP) with adenine as a bridge ligand was employed to integrate with alkaline phosphatase (ALP) and anticarcinoembryonic antigen (anti-CEA) antibody, which produces ALP/anti-CEA@ZnCPs. Benefiting from the adaptive inclusion property of ZnCPs, the integrated ALP and anti-CEA can maintain their original catalytic activity and capture ability to target antigen, respectively. This allows the ALP/anti-CEA@ZnCPs to be a detection antibody for performing an immunoassay. Meanwhile, ZnCP as a host can effectively protect the loaded ALP and anti-CEA against harsh environments. On this basis, by using iron(II)-phenanthroline complex as a signal amplifier, a colorimetric immunoassay for CEA detection was developed, and a low detection limit of 21.1 pg/mL has been achieved. This immunoassay was successfully applied to determine CEA levels in serum samples with good recovery and precision. We believe that this study can not only provide a new method for CEA detection but also open up a new way for the rational design and fabrication of multifunctional composites.