Homogenous cathodic photoelectrochemistry for DNA binding protein analysis

We herein demonstrate a homogeneous and label-free cathodic photoelectrochemical (PEC) bioassay for DNA binding protein analysis, which shows the distinctive advantages of facile operation, cost/time saving, and high sensitivity. The binding of the NF-kappa B p50 protein (a model analyte of the DNA binding protein) to its binding sequences determines the occurrence of the subsequent rolling circle amplification (RCA) reaction, and thus regulates the production of free or intercalated (in G-quadruplex motifs) methylene blue (MB) for stimulating the cathodic photocurrent of CuBi2O4. The result reveals that it allows an economical, convenient and preferable platform for the NF-kappa B p50 protein assay because it avoids both surface-based operations and labeling of biomolecules. Moreover, this homogeneous cathodic PEC strategy facilitates unblocked signal transduction for producing high sensitivity, the linear range from 5.0 pM to 10.0 nM with a low detection limit of 3.0 pM (S/ N = 3). Importantly, the feasibility of free/intercalative MB as a signaling molecule of photocathodes enables the successful demonstration of a homogeneous cathodic photoelectrochemistry, which hints the prospects of other ingenious signaling molecules to be integrated with different DNA motifs for exquisite cathodic PEC bioassays.