A label-free electrochemistry biosensor based flower-like 3-dimensional ZnO superstructures for detection of DNA arrays

A novel label-free DNA hybridization biosensor was fabricated using flower-like 3-dimensional (3D) ZnO superstructures as an enhanced sensing platform and employing chitosan (CS) as a film-forming material. A highly sensitive electrochemical DNA sensor was constructed by homogenously distributing Au nanoparticles (AuNPs) on the ZnO-CS matrix. The electrochemical performance of the designed electrodes was investigated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Differential pulse voltammetry (DPV) was used to monitor DNA hybridization. The AuNPs/ZnO-CS film exhibited good conductivity for accelerating the electron transfer, which led to obvious signal amplification and a low detection limit for electrochemical sensing. Under optimal conditions, the peak currents of the redox marker exhibited a linear relationship with the logarithm of the concentrations of complementary DNA from 1.0 × 10^-14 to 1.0 × 10^-10 M with a detection limit of 2.0 × 10^-15 M (3σ/S). The developed sensor also displayed high selectivity to differentiate one-base mismatched DNA. The excellent performance of the biosensors was attributed to large surface-to-volume of ZnO superstructures and the synergistic effect of AuNPs and CS. The proposed approach provides a simple and reliable method for DNA detection and will open new opportunities for the sensitive detection of other nucleic acids.