Protein detection based on small molecule-linked DNA.

Based on small molecule-linked DNA and the nicking endonuclease-assisted amplification (NEA) strategy, a novel electrochemical method for protein detection is proposed in this work. Specifically, the small molecule-linked DNA (probe 1) can be protected from exonuclease-catalyzed digestion upon binding to the protein target of the small molecule, so the DNA strand may hybridize with another DNA strand (probe 2) that is previously immobilized onto an electrode surface. Consequently, the NEA process is triggered, resulting in continuous removal of the DNA strands from the electrode surface, and the blocking effect against the electrochemical species [Fe(CN)(6)](3-/4-) becomes increasingly lower; thus, increased electrochemical waves can be achieved. Because the whole process is activated by the target protein, an electrochemical method for protein quantification is developed. Taking folate receptor (FR) as an example in this work, we can determine the protein in a linear range from 0.3 to 15 ng/mL with a detection limit of 0.19 ng/mL. Furthermore, because the method can be used for the assay of FR in serum samples and for the detection of other proteins such as streptavidin by simply changing the small molecule moiety of the DNA probes, this novel method is expected to have great potential applications in the future.