Application of Antibody-Powered Triplex-DNA Nanomachine to Electrochemiluminescence Biosensor for Detection of Anti-Digoxigenin with Improved Sensitivity versus Cycling Strand Displacement Reaction.

The accurate and rapid quantitative detection of antibodies had a significant influence in controlling and preventing diseases or toxins outbreaks. In this work, we first introduce the antibody-powered triplex-DNA nanomachine to release cargo DNA as substitute target for sensitive electrochemiluminescence (ECL) detection of anti-digoxigenin based on a novel ternary ECL system. It is worth noting that the cargo DNA as a substitute target of antibody can further participate in an enzyme-assisted cycling strand displacement reaction (CSDR) to achieve ECL signal amplification and improve the sensitivity of antibody detection. Additionally, porous palladium nanospheres (pPdNSs) with considerably catalytic activity were first applied as co-reaction accelerator to efficiently enhance the intensity of the ECL system of rubrene microblocks (RubMBs) as luminophore and dissolved O2 as endogenous co-reactant. With the resultant ternary ECL system as biosensing platform, a significantly enhanced initial signal was achieved in advance. Then the ferrocene labeled quenching probes were employed to reduce initial signal and obtain the low background signal. Eventually, the cargo DNA made the quenching probes release and recover the signal in the presence of anti-digoxigenin. Thereupon the wide linear range (0.01-200 nM) and low limit of detection (6.7 pM) were obtained, and this method not only reduces conjugation steps, but also provides a sensitive and novel ECL analysis platform for trace detection of other antibodies and antigen.