▎ 摘　　要

Graphene oxide (GO)-Chitosan (CHI) nano-composite is employed for the development of DNA based electrochemical biosensor for diagnosis of typhoid. Biosensor has been prepared by covalent immobilization of Salmonella typhi specific 5'-amine labeled single stranded (ss) DNA probe on GO-CHI/ITO via glutaraldehyde. Differential pulse voltammetry (DPV) studies revealed good specificity and ability of ssDNA/GO-CHI/ITO biosensor to distinguish complementary, non-complementary and one base mismatch sequences. The ssDNA/GO-CHI/ITO biosensor showed detection range of 10 fM to 50 nM and LOD 10 fM within 60 s hybridization times for complementary sequence. Further, ssDNA/GO-CHI/ITO bioelectrode is able to detect complementary target present in serum samples with LOD of 100 fM at 25 degrees C. The excellent performance of biosensor is attributed to large surface-to-volume ratio and good electrochemical activity of graphene oxide, and good biocompatibility of chitosan, which enhances the DNA immobilization and facilitate electron transfer between DNA and electrode surface (ITO). (C) 2013 Elsevier B.V. All rights reserved.