Highly sensitive electrochemiluminescence biosensor for Dam methyltransferase based on target-response DNA hydrogel

A highly sensitive electrochemiluminescence (ECL) biosensor for Dam methyltransferase (MTase) detection based on target-response DNA hydrogel has been designed. The hydrogel is composed of hyaluronic acid sodium salt (HA), double strands DNA (dsDNA) that formed from two amine modified oligonucleotides, a little polyethylenimine (PEI) and plenty of ECL signal probes (Ru(bpy)32+-doped SiO2 nanoparticles (Ru@SiO2 NPs)). The dsDNA has been carefully designed, which can be recognized and methylated by Dam MTase and be specifically decomposed by DpnI in turn. When target (Dam MTase) existed, DNA in hydrogel was destroyed by DpnI,which results in the leakage of signal probes into the supernatant and strong ECL signal can be obtained. Without target, DpnI enzyme cannot cut unmethylated DNA, signal probes cannot be released, and low ECL signal can be detected from the supernatant. The ECL intensity detected has a good linear relationship with the target concentration in the range of 0.05–40U/mL, and the limit of detection is 0.02U/mL. The proposed method shows good selectivity and reproducibility, and the prepared hydrogel has good storage stability. The biosensor has been successfully applied for Dam MTase detection in human serum samples and potential inhibitor screening with satisfactory results.