An electrochemical biosensor based on the enhanced quasi-reversible redox signal of prussian blue generated by self-sacrificial label of iron metal-organic framework.

We develop for the first time a new electrochemical biosensor for signal-on detection of T4 polynucleotide kinase (PNK) based on the enhanced quasi-reversible redox signal of prussian blue generated by self-sacrificial label of iron metal-organic framework (FeMOF). The DNA hairpin probe modified with FeMOF@AuNPs at the 3'-thiol end acts as the substrate of PNK. The presence of PNK enables the 5'-phosphorylation of hairpin probe, which may subsequently function as the substrate of lambda exonuclease. Lambda exonuclease removes the 5' mononucleotides from the stem, unfolding the hairpin structure and releasing the single-stranded DNA (ssDNA). The resultant FeMOF@AuNP-modified ssDNA may specifically hybridize with the capture probe to form the double-strand DNA (dsDNA) duplex, enabling the immobilization of FeMOF on the electrode surface. The reaction of Fe3+ in the MOF with K4Fe(CN)6 leads to the formation of prussian blue on the electrode surface and consequently the generation of a high electrochemical signal. This assay is very simple without the involvement of the pre-synthesized prussian blue which is unstable in neutral buffer, and the self-sacrificial label of FeMOF can achieve great signal amplification without the involvement of any extra functional materials. Due to the introduction of self-sacrificial label of FeMOF and the formation of prussian blue nanolayers with good quasi-reversible cyclic voltammetric electrochemical activity, this biosensor exhibits high sensitivity and a large dynamic range. Moreover, this biosensor can be used to screen the PNK inhibitors, holding great potential in disease diagnosis and drug discovery.