Designed zwitterionic peptide combined with sacrificial Fe-MOF for low fouling and highly sensitive electrochemical detection of T4 polynucleotide kinase

Abstract Herein, an antifouling and sensitive electrochemical enzyme sensing platform was developed based on a self-designed zwitterionic peptide and sacrificial iron metal-organic framework (Fe-MOF). The designed zwitterionic peptide was hydrophilic and neutral in charge, and it was used to improve the antifouling capability of the sensing system. Fe-MOF with amine groups was loaded with Au nanoparticles and further functionalized with a specific DNA sequence, and it was used as a sacrificial label. The sensing target, T4 polynucleotide kinase (PNK), can catalyze the 5’-hydroxyl termini of a unique hairpin DNA to phosphate group, and the hairpin DNA can then be hydrolyzed by lambda exonuclease (λ-Exo) and release a single nucleotide. In the presence of the released DNA sequence, a sandwich-type hybridization reaction was triggered, and the DNA linked Fe-MOF was selectively attached to the electrode surface, which can react with K4Fe(CN)6 to form the electroactive Prussian blue and generate significantly enlarged current response. Based on the antifouling peptide and the sacrificial Fe-MOF, the biosensor exhibited satisfying analytical performance for the detection of T4 PNK, with a wide linear range from 1.0×10-3 to 10 U·mL-1 and a low detection limit of 3.5×10-4 U·mL-1. Moreover, the biosensor was capable of effectively eliminating nonspecific protein adsorption and assaying target in human serum, indicating its promising potential for practical application.