Electrochemical genosensor based on carboxylated graphene for detection of water-borne pathogen

This work reports the application of newly synthesized carboxylated graphene nanoflakes (Cx-Gnfs). The Cx-Gnfs were synthesized by wet chemical method in sulfuric acid/nitric acid mixture and was further electrophoretically deposited on indium tin oxide (ITO) coated glass substrates using Mg2+ ions which provides an overall charge to the materials for deposition onto the anode. The materials were characterized using SEM, TEM, contact angle, UV-vis spectroscopy, FT-IR, XRD and electrochemically characterized by cyclic voltammetry, chronocoulometry and electrochemical impedance spectroscopy. The sensitive quantitative determination of nucleic acid Escherichia coli O157: H7 (E. coli) has been achieved using Cx-Gnfs and r-GO as the sensing layer using electrochemical impedance spectroscopy. The electrochemical results reveal that the Cx-Gnfs based genosensor exhibits a linear response to complementary DNA (10−6 M to 10−17 M) with a detection limit of 1 × 10−17 M while the rGO based genosensor shows a detection limit of 1 × 10−15 M. Under optimal conditions, this Cx-Gnfs based genosensor was found to retain about 85% of its initial activity after being used for 6 times.