Electrochemical detection of carcinoembryonic antigen in human serum based on designed anti-fouling and anti-enzymolysis peptides conjugated with silk sericine-inspired beta-homoserine

Zwitterionic peptides with strong water binding ability have drawn much attention in the biomedical diagnosis field as antifouling materials. However, the proteolytic susceptibility of natural peptides in human serum or blood greatly limited their practical application. Herein, inspired by the strong stability and biocompatibility of sericin, an extended zwitterionic peptide containing unnatural β-homoserine (pβ-peptide) was designed to construct antifouling biosensors with enhance stability in complex biological fluids. The molecular dynamic simulation illustrated the strong water binding capability of the pβ-peptide owing to the formation of a large quantity of hydrogen bonds with water. Compared with the electrodes modified with normal peptide, ones modified with the designed peptide demonstrated much stronger antifouling capability and significantly enhanced stability when evaluated in human serum and blood. Furthermore, the constructed biosensor integrating the designed antifouling peptide with carcinoembryonic antigen (CEA) aptamer exhibited a great sensitivity for detecting CEA protein, with a broad linear range of 1.0 fg·mL−1-1.0 ng·mL−1 and a low detection limit of 0.33 fg·mL−1. The biosensor was competent to accurately assay CEA in clinical serum samples when compared with the commonly adopted ELISA method, which indicates a promising potential for practical applications.