An electrochemical biosensor for alpha-fetoprotein detection in human serum based on peptides containing isomer D-Amino acids with enhanced stability and antifouling property.

The development of antifouling biosensors capable of detecting biomarkers at low concentrations in complex bio-fluids with many interference components is of great importance in the diagnosis and treatment of diseases. Certain zwitterionic peptides composed of natural L-amino acids have been used for the construction of low fouling biosensors and demonstrated excellent antifouling performances, but they are prone to enzymatic degradation in biological media, such as serum that contains a variety of enzymes. In this work, a novel antifouling peptide with the sequence of cppPPEKEKEkek was designed, and three unnatural D-amino acids were set at both ends of the peptide to enhance its tolerance to enzymatic degradation. An electrochemical biosensor was constructed by coupling the antifouling peptide with a conducting polymer polyaniline (PANI) to achieve accurate detection of alpha-fetoprotein (AFP) in clinical samples. Owing to the presence of the designed peptide with partial D-amino acids (pD-peptide), the biosensing interface showed significantly high antifouling performance and enhanced stability in human serum. Meanwhile, the pD-peptide based biosensor exhibited high sensitivity toward the target AFP, with the linear range from 0.1 fg mL-1 to 1.0 ng mL-1 and the limit of detection of 0.03 fg mL-1 (S/N = 3). This strategy of enhancing the stability (tolerance to enzymolysis) of antifouling peptides in biological samples provided an effective way to develop antifouling biosensors for practical applications.