Abstract
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.
1. Introduction
The nucleic acid test with high sensitivity and specificity is very important of central importance, especially in the field of diseases (Fan et al., 2006; Farjami et al., 2011), molecular diagnosis (Zhou et al., 2014), biomedical research (Palecek et al., 2012), medicine exploitation (Meng et al., 2016; Zhu et al., 2013), environmental monitoring (Zhou et al., 2017) and food safety (Li et al., 2010). Various strategies and technologies have been developed to identify unique DNA sequences. Agarose, and polyacrylamide gel electrophoresis (Southern, 1975; Zhu et al., 2015), real-time polymerase chain reaction (RT-PCR) (Doi et al., 2015), DNA microarrays (gene chip) (Cho and Tiedje, 2002), the surface Plasmon resonance BIAcore instrument (Ding et al., 2017) and GeneXpert system (Jones et al., 2001) have been used as standard procedures in research laboratories.
4. Conclusions
We have developed a highly selective and ultrasensitive DNA biosensor using electrochemically mediated surface-initiated atom transfer radical polymerization (ATRP) signal amplification and “Click Chemistry”. Under optimal conditions, the biosensor was capable of detecting minimum 0.2 aM. target DNA. The preliminary application of the developed DNA biosensor was demonstrated by detecting target DNA in spiked serum samples. More optimizations are required to shorten the total assay time for real biosensor applications. The developed DNA biosensor shows great promise for the detection of gene biomarkers such as microRNA.
