Designed multifunctional peptides with two recognizing branches specific for one target to achieve highly sensitive and low fouling electrochemical protein assay in human serum

Herein, an antifouling electrochemical biosensor based on designed multifunctional peptides with two recognizing branches specific for one target was proposed to improve the target recognition efficiency and sensitivity. The designed multifunctional peptide contains two different recognizing branches (with sequences FYWHCLDE and FYCHTIDE) for immunoglobulin G (IgG), an antifouling sequence (EKEKEK) and an anchoring sequence (CPPPP), which can be immobilized onto the gold nanoparticles (AuNPs) and poly(3,4-ethylenedioxythiophene) (PEDOT) modified electrode surface. Owing to the synergistic effect of the two recognizing branches, the dual-recognizing peptide-based biosensor exhibited significantly enhanced sensitivity. Under the optimal experimental conditions, the biosensor for IgG exhibited a linear response range of 0.1 pg/mL to 0.1 μg/mL, with a limit of detection of 0.031 pg/mL (about 2 orders of magnitude lower than that of the normal biosensor). Moreover, the biosensor was also capable of assaying IgG in real biological samples such as human serum without suffering from significant biofouling. This strategy for biosensor construction not only ensures the ultra-sensitivity for target detection, but also effectively avoids biofouling on sensing interfaces in complex biological media.