Tungsten disulfide nanosheets supported poly(xanthurenic acid) as a signal transduction interface for electrochemical genosensing applications.

Tungsten disulfide (WS2) nanosheets supported poly(xanthurenic acid) (PXa) was used as the signal transduction interface for electrochemical genosensing. The WS2 nanosheets were obtained from bulk WS2 using a simple ultrasonic method. Due to the unique physical adsorption of Xa monomers to WS2, the electropolymerization efficiency was greatly improved, accompanied with an increased electrochemical response of PXa. The obtained PXa/WS2 nanocomposite not only served as a substrate for DNA immobilization but also reflected the electrochemical transduction originating from DNA immobilization and hybridization without any other indicators or complicated labelling steps. Owing to the presence of abundant carboxyl groups, the probe ssDNA was covalently attached on the carboxyl-terminated PXa/WS2 nanocomposite through the free amines of DNA sequences based on the 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide and N-hydrosulfosuccinimide crosslinking reaction. The covalently immobilized probe ssDNA could selectively hybridize with its target DNA to form dsDNA on the surface of the PXa/WS2 nanocomposite. This developed biosensor achieved a satisfactory detection limit down to 1.6 × 10-16 mol L-1 and a dynamic range of 1.0 × 10-15 to 1.0 × 10-11 mol L-1 for detection of circulating tumor DNA related to gastric carcinoma. Selectivity of the biosensor has been investigated in presence of non-complementary, one-mismatched and two-mismatched DNA sequences.