Dendrimers-based DNA biosensors for highly sensitive electrochemical detection of DNA hybridization using reporter probe DNA modified with Au nanoparticles.

A novel and sensitive electrochemical approach for sequence-specific DNA detection based on polyamidoamine (PAMAM) and signal amplification with nanoparticles (NPs) is reported. A gold electrode was first modified with 3-mercaptopropionic acid, and then reacted with an amino-terminated polyamidoamine (PAMAM, G 4.0-NH(2)) to obtain a thin film. Single-stranded 3'-biotin end-labeled oligonucleotide was immobilized onto the film to obtain a stable recognition layer through biotin-avidin combination to detect complementary target, using signal amplification with Au NPs and [Ru(NH(3))(6)](3+) as redox electroactive indicators. The properties of the avidin/PAMAM/3-mercaptopropionic acid (RSH)/Au, the characteristics of the immobilization and hybridization of DNA were studied by cyclic voltammetry (CV), difference pulse voltammetry (DPV) and electrochemical impedance spectroscopy. The dynamic detection range of the sequence-specific DNA was from 1.4 x 10(-11) to 2.7 x 10(-14) mol L(-1) and the detection limit was 1.4 x 10(-14) mol L(-1). The DNA sensor not only showed low detection limit, but also exhibited excellent selectivity against two-base mismatched DNA.