Ultrasensitive DNA biosensor based on electrochemical atom transfer radical polymerization.

Here we report a highly selective and ultrasensitive DNA biosensor based on electrochemical atom transfer radical polymerization (ATRP) signal amplification and "Click Chemistry". The DNA biosensor was prepared by immobilizing thiol and azide modified hairpin DNAs on gold electrode surface. In the presence of target DNAs (T-DNA), hairpin probes hybridized with T-DNAs to form a duplex DNA, and the ring of hairpin DNA was opened to make azide groups accessible at 3' ends. "Click reactions" proceeded between the azide and propargyl-2-bromoisobutyrate (PBIB) to initiate the ATRP reaction which brought a large number of ferrocenylmethyl methacrylate (FMMA) on the electrode surface. The amount of FMMA was proportional to the concentration of T-DNA and quantified by square wave voltammetry. Combining ATRP signal amplification with "Click Chemistry", the optimized DNA biosensor was capable of detecting 0.2 aM. T-DNA. The preliminary application of the developed DNA biosensor was demonstrated by detecting target DNA in spiked serum samples. The developed DNA biosensor shows great promise for the detection of gene biomarkers.