Determination of Transcription Nuclear Factor-Kappa B Using an Electrochemical, DNA-Based Nanoswitch

Highly sensitive electrochemical nuclear factor kappa B aptasensor based on target-induced dual-signal ratiometric and polymerase-assisted protein recycling amplification strategy

In this work, an amplified electrochemical ratiometric aptasensor for nuclear factor kappa B (NF-κB) assay based on target binding-triggered ratiometric signal readout and polymerase-assisted protein recycling amplification strategy is described. To demonstrate the effect of "signal-off" and "signal-on" change for the dual-signal electrochemical ratiometric readout, the thiol-hairpin DNA (SH-HD) hybridizes with methylene blue (MB)-modified protection DNA (MB-PD) to form capture probes, which is rationally introduced for the construction of the assay platform. On the interface, the probes can specifically bind to target NF-κB and expose a toehold region which subsequently hybridizes with the ferrocene (Fc)-modified DNA strand to take the Fc group to the electrode surface, accompanied by displacing MB-PD to release the MB group from the electrode surface, leading to the both "signal-on" of Fc (I_Fc) and "signal-off" of MB (I_MB). In order to improve the sensitivity of the electrochemical aptasensor, phi29-assisted target protein recycling amplification strategy was designed to achieve an amplified ratiometric signal. With the above advantages, the prepared aptasensor exhibits a wide linear range of 0.1pgmL^-1 to 15ngmL^-1 with a low detection limit of 0.03pgmL^-1. This strategy provides a simple and ingenious approach to construct ratiometric electrochemical aptasensor and shows promising potential applications in multiple disease marker detection by changing the recognition probe.

Nanostructured gold dsDNA sensor for early detection of breast cancer by beta protein 1 (BP1)

Beta protein 1 (BP₁) is a homeobox protein expressed in 80% of breast cancer cells in either estrogen receptor (ER) positive or ER negative breast cancer. However, it is barely detectable in normal breast tissues. In this project we present an electrochemical DNA nanostructured gold biosensor for detection of BP₁. The gold sensor is first electrochemically nanostructured in 0.5 M sulfuric acid to reach superior conductivity, larger surface area, and higher stability. Nanostructured gold surface was characterized by atomic force microscopy (AFM) and scanning electron microscopy (SEM). The nanostructured gold sensor is then modified with double-stranded (ds) DNA mapping the genomic sequence that contains the binding site for BP₁. A redox-active probe (methylene blue) was intercalated in dsDNA to monitor the binding event of BP₁. A linear correlation of the electrochemical response by concentration of BP₁ was obtained (R² = 0.998) with a limit of detection of 1.2 nM. This nanostructured gold dsDNA sensor is shown to be sensitive, selective, stable, and reusable allowing for its potential clinical use.