Dual Signal Amplification by eATRP and DNA-Templated Silver Nanoparticles for Ultrasensitive Electrochemical Detection of Nucleic Acids

Herein, an ultrasensitive and novel platform for DNA detection is reported, which combines DNA-templated silver nanoparticles (AgNPs) with electrochemical atom transfer radical polymerization signal amplification. Peptide nucleic acid (PNA) functionalized with thiol was modified to the Au electrode surface as a probe to specifically capture target DNA (T-DNA). After Zr4+ binds to phosphate on DNA, the initiator [α-bromophenylacetic acid (BPAA)] of ATRP is attached to PNA/DNA heteroduplexes based on the phosphate groups of T-DNA and carboxylate groups of BPAA via zirconium–phosphate–carboxylate chemistries. A large number of glyco-syloxyethyl methacrylates (GEMA) were captured on the formed PNA/DNA duplex via ATRP. Afterwards, the polysaccharides were oxidized to polymerized aldehydes with sodium periodate (NaIO4). In addition, AgNPs were deposited on the electrode surface by silver mirror reaction. The results indicate that the amount of AgNPs proportional to the T-DNA was quantified through differential pulse voltammetry. Furthermore, it proves that the modified electrode has good performance in DNA detection, indicating that the DNA sensor has high selectivity, high sensitivity, and stable repeatability. Under the optimal conditions, a good linear relationship is obtained in the range of 10 aM to 10 pM with the correlation coefficient of 0.992, and the detection limit is calculated to be as low as 4.725 aM. In addition, the sensor is successfully used to detect DNA in actual serum samples with satisfactory results, which indicates huge promise for detecting gene biomarkers and clinical analysis.