A Sensitive Electrochemical Assay for T4 Polynucleotide Kinase Activity Based on Fe3O4@TiO2 and Gold Nanoparticles Hybrid Probe Modified Magnetic Electrode

An ultrasensitive electrochemical assay for T4 polynucleotide kinase (T4 PNK) activity and inhibition was developed based on magnetic Fe3O4@TiO2 core–shell nanoparticles and gold nanoparticles hybrid probe (Fe3O4@TiO2-dsDNA-AuNPs) modified magnetic gold electrode (MGE). Fe3O4@TiO2-dsDNA-AuNPs hybrid probe was formed via DNA hybridization between phosphorylated DNA S1 modified Fe3O4@TiO2 and complementary DNA S2 assembled AuNPs. [Ru(NH3)6]3+ was used as an electrochemically active indicator to enhance the electrochemical signal. The proposed method is sensitive for T4 PNK activity assay with a linear range of 0.0001 to 10 U ml−1 and low detection limit of 0.00003 U ml−1. This strategy can be used to screen the T4 PNK inhibitors, holding a great potential for discovery of nucleotide kinase-target drug and early clinical diagnosis of cancer.