DNA nanomachine-assisted magnetic bead based target recycling and isothermal amplification for sensitive fluorescence determination of interferon-γ

The authors describe a protein-triggered self-assembling DNA nanomachine for the detection of interferon-γ (IFN-γ), an important cytokine associated with immuno response. The DNA nanoprobe exhibits good specificity and sensitivity for interferon-γ (IFN-γ) detection. In the presence of the target (IFN-γ), four functional DNA probes are assembled to form a DNA nanocomplex. It promotes the release of the target for recycling. The captured DNA probe (biotinylated-C1) is then brought into contact with streptavidin-functionalized magnetic beads (sa-MB). These cause the dissociation of the B3 primer signal probe (S1) from the reaction solution which then is available for loop-mediated isothermal amplification (LAMP) analysis. As the deficiency of the B3 primer inhibits the LAMP reaction, the resulting point of inflexion (POI) value (the starting point of LAMP) is increased. In the absence of IFN-γ, the operation of the DNA nanomachine is not triggered, and the LAMP reaction remains unaffected. In this way, the POI values indirectly report the concentration of IFN-γ. The feasibility of the protein-driven DNA nanomachine was first demonstrated by the gel electrophoresis and real-time fluorescence analysis. Then, under optimal conditions, IFN-γ in concentrations as low as 5 ng·mL can be quantified, and the detection limit is 2.3 ng·mL. Besides, this strategy can effectively discriminate IFN-γ from other proteins and displayed acceptable recoveries even in serum samples. In our perception, this approach holds great promise as it may be adapted to detect numerous other proteins. [Figure not available: see fulltext.].