A novel and ultrasensitive electrochemical DNA biosensor based on an ice crystals-like gold nanostructure for the detection of Enterococcus faecalis gene sequence.

Bacteria, parasites and viruses are found widely in the environment as potential pathogens, and can be the source of infections. Therefore, sensitive and rapid methods for identification of the pathogens are required to achieve a better quality of life. Enterococcus faecalis commonly colonizes and threatens human health. In the present study, we demonstrate the fabrication of a novel electrochemical DNA biosensor based on electrodeposited gold nanostructures as a transducer substrate combined with toluidine blue (TB) as a redox marker. Binding of TB with the single and double stranded DNA (ssDNA and dsDNA) was shortly investigated, and based on the results, TB could discriminate between ssDNA and dsDNA. A specific thiolated ssDNA sequence was immobilized on the transducer substrate, and DNA hybridization was followed by differential pulse voltammetry. The DNA biosensor showed excellent performances with high sensitivity and good selectivity. The DNA biosensor was applied to detect a synthetic target in a linear range of 1.0 × 10-17-1.0 × 10-10 mol L-1 with a limit of detection (LOD) of 4.7 × 10-20 mol L-1. In addition, LOD of the DNA biosensor for the detection of genomic DNA was found to be 30.1 ng μL-1.