Aptamer based voltammetric biosensor for Mycobacterium tuberculosis antigen ESAT-6 using a nanohybrid material composed of reduced graphene oxide and a metal-organic framework.

The 6-kDa early secretory antigenic target referred to as ESAT-6 is a virulence factor secreted by Mycobacterium tuberculosis (MTB). This work describes a voltammetric aptasensor for ultrasensitive detection of ESAT-6. Reduced graphene oxide doped with metal-organic framework (MOF-rGO) was deposited on a glassy carbon electrode (GCE). This increases the immobilization of electroactive Toluidine Blue (TB) and facilitates the electron transfer from TB to the modified GCE. Platinum/gold core/shell (Pt@Au) nanoparticles were used to assemble thiolated ESAT-6 binding aptamer (EBA) on a modified electrode and to further amplify the response to TB. The modified GCE, typically operated at -0.36 V (vs. SCE), has a linear response in 1.0 × 10-4 to 2.0 × 102 ng⋅mL-1 ESAT-6 concentration range, and the limit of detection (LOD) for ESAT-6 is as low as 3.3 × 10-5 ng⋅mL-1. It exhibits satisfactory specificity and reproducibility when analyzing spiked human serum. Graphical abstract Schematic presentation of a voltammetric aptasensor for Mycobacterium tuberculosis antigen ESAT-6 using a glassy carbon electrode modified with reduced graphene oxide (rGO) and a metal-organic framework (MOF). The limit of detection for ESAT-6 is as low as 3.3 × 10-5 ng/mL.