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

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 K 4 Fe(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.