Electrochemical strategies coupled to a genomagnetic assay for the detection of M. Tuberculosis

Abstract

Tuberculosis (TB) is often a deadly infectious disease, especially in the developing countries, where association with HIV/AIDS constitutes a lethal combination. Although efficient, rapid diagnosis is critical for successful control of TB, most detection methods are slow (culturing methods) or need special and expensive instrumentation as well as trained personnel (molecular methods), difficult to find in those countries. Genetic identification and quantification based on hybridization of specific sequences coupled to electrochemical detection becomes a cost-effective alternative for a rapid diagnosis because of their easy miniaturization and inexpensive equipment[1]. In this work a short sequence of the IS6110 insertion element exclusively found on M. tuberculosis complex was selected as the target for a genomagnetic assay. Because of the enhanced selectivity of structured probes[2], a hairpin capture probe was designed and attached to streptavidin-coated magnetic beads. A sandwich-format assay allowed the specific recognition of the target using a biotinylated signaling-DNA probe. Two electrochemical detection strategies were compared. Both of them relied on the detection of an electrochemically active product of a streptavidin-enzyme conjugate, capturing the modified beads on the surface of disposable carbon screen-printed electrodes by a small magnet. The enzymatically generated products of alkaline-phosphatase and horseradish peroxidase