Speckled ZnO nanograss electrochemical sensor for staphylococcus epidermidis detection

Zinc oxide nanograss (ZnONG) decorated with gold (Au) nanospeckles is demonstrated as a sensing platform for bacterial DNA hybridization in this study. Thermal evaporation of 5 nm Au on hydrothermally synthesized ZnONG generates highly dense speckles, which contributes to an approximately two-fold enhancement of the effective surface area and diffusion coefficient in cyclic voltammetry (CV) measurement compared to the non-speckled nanograss. Selective capture of molecular probes from our predesigned sequence of S. epidermidis 16S rRNA onto nanospeckled ZnONG indicated a specific interaction with the DNA target from this prevalently isolated skin pathogen through hybridization screening. The fabricated DNA biosensor demonstrated great ability to quantify a wide range of complementary DNA target, from 10 pM to 1 μM. Moreover, it attained an impressive limit of detection (LOD) of 0.506 pM, as determined by the charge-transfer resistance (R_CT), upon DNA hybridization in an electrochemical impedance spectroscopy (EIS) analysis. The proposed structure of the hybrid Au-speckled ZnONG effectively improved the electrocatalytic properties and electron migration of electrochemical DNA detection due to the increment of the surface area, which consequently renders this structure a potential platform for array-based DNA sensor development.