DNA-Electrochemical biosensor for the detection single nucleotide mutation in rifampicin-resistant Mycobacterium Tuberculosis using Au-modified carbon screen printed electrodes (SPEs)

Abstract

Tuberculosis (TB) remains a leading cause of death globally, especially in underdeveloped nations. The main impediment to TB eradication is a lack of efficient diagnostic tools available for the disease diagnosis. In this work, label free and ultrasensitive electrochemical DNA biosensor for the detection of IS6110 and single nucleotide mutation in rpoB gene Mycobacterium tuberculosis and has been developed, based on electrodeposition of gold nanoparticles on the surface of carbon screen-printed electrode (Zensors) for the signal amplification. Particularly, screen-printed electrodes were modified by electrochemical deposition of Au to enhance the conductivity and to facilitate the immobilization of ssDNA probes via Au-S bonds. The electrochemically modified SPEs were characterized using SEM/EDX and XRD. Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques were used to investigate the DNA hybridization between ssDNA probe and target DNA (tDNA). Under the ideal conditions, biosensor exhibited correlation coefficient R2 = 0.993, when analyzed with different tDNA concentrations. Due to the large surface area and super conductivity, designed biosensor displayed ultrasensitive detection of tDNA, with the detection limit of 1.3nM, 2.27pM and 2.9pM for IS6110, 516 mutation and 531 point mutations respectively. The biosensor, under ideal conditions, distinguishes non-complementary DNA from perfectly matched tDNA. By eliminating the need for DNA purification, this work paves the path for the creation of disposable biosensors capable of detecting DNA from raw sputum samples.