Evaluation of an Ag85B Immunosensor with Potential for Electrochemical Mycobacterium Tuberculosis Diagnostics

Brian Murphy,Eithne Dempsey

doi:10.1149/2162-8777/aba993

Abstract

Tuberculosis remains a major global health concern, especially in the developing world, and monitoring/early detection of the disease relies on low cost technologies that provide rapid and accurate results. Mycobacterium tuberculosis is the responsible bacterial pathogen and it is currently estimated by the World Health Organisation (WHO), that one quarter of the world’s population, mainly in the developing world, is infected with TB. The overall aim of this work was to advance a screening electrochemical sensor for label free detection of Ag85B, a member of the Antigen 85 complex—major secretary protein of M. tuberculosis and biomarker for disease. An indirect ELISA Ag85B assay was optimised with capture antibody and antigen levels determined via a checkerboard titration (0.625 μg ml−1 and 2.5 μg ml−1 respectively). Following assay development, crosslinking of the bioreceptor Anti-Ag85B onto electrochemically deposited gold nanoparticle (AuNP) modified carbon electrodes was achieved and Ag85B binding successfully evaluated electrochemically via cyclic voltammetry. Following each modification step, ΔEp of a redox probe was monitored and overall results show that GCE/AuNP/anti-Ag85B electrochemical transducers are a viable method for Ag85B detection, capable of measuring antigen levels <2.5 μg ml−1.

Highlights

TB is a major global threat and according to the WHO approximately 1.7 million annual deaths are attributed to TB [1] with the disease being most prevalent in Asia (58%) and the African region (28%)
TB can exist both as an active and latent disease and the Mycobacterium tuberculosis life cycle can be separated into three main stages, latent, reactivating and active TB
In order to treat an infection effectively it is ev paramount that accurate and timely diagnosis is performed, preferably at the point of care (POC)

Summary

Introduction

TB is a major global threat and according to the WHO approximately 1.7 million annual deaths are attributed to TB [1] with the disease being most prevalent in Asia (58%) and the African region (28%). Emergence of multi-drug resistant strains and co-infections with human immunodeficiency (HIV) make for high prevalence and early diagnosis is key for us disease control. Active TB is responsible for the symptoms mentioned above an while patients suffering latent TB show no signs or symptoms of the disease but are at risk of developing the active form of the disease [3]. In order to treat an infection effectively it is ev paramount that accurate and timely diagnosis is performed, preferably at the point of care (POC). In high-burden, resource-limited countries sputum smear microscopy is used as a iew primary tool provided there are suitable facilities and a trained microscopist on site with the need for patients to make several visits for accurate diagnosis. The WHO reports that in high-burden countries a significant number of patients fail to return to collect their smear

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