Chitosan-iron oxide nano-composite platform for mismatch-discriminating DNA hybridization for Neisseria gonorrhoeae detection causing sexually transmitted disease

Electrochemically fabricated nano-composite film of chitosan (CH)-iron oxide (Fe3O4) has been used to detect gonorrhoea, a sexually transmitted disease (STD) via immobilization of biotinylated probe DNA (BDNA) using avidin-biotin coupling for rapid and specific (mismatch-discriminating) DNA hybridization. The presence of Fe3O4 nanoparticles (similar to 18 nm) increases the electro-active surface area of the nano-biocomposite that provides desirable environment for loading of DNA with better conformation leading to increased electron transfer kinetics between the medium and electrode. The differential pulse voltammetric (DPV) studies have been conducted using BDNA/avidin/CH-Fe3O4/ITO electrode owing to the reduction of the methylene blue (MB) indicator and investigate electron transfer between MB moieties and electrode for one and two-bases mismatch. This STD biosensor is found to have a detection limit (1 x 10(-15) M) and a wide dynamic range (from 1 x 10(-16) M to 1 x 10(-6) M) using the complementary target DNA. In addition, the sensing system can be utilized to accurately discriminate complementary sequence from mismatch sequences. (C) 2010 Elsevier B.V. All rights reserved.