Optical biosensing of mycolic acid biomarker for TB diagnosis

Abstract

When it comes to diagnostics for various microorganisms, biosensors offer great advantages over conventional analytical techniques. Specifically, they can provide multiple capabilities such as user-friendly operation, real-time analysis, rapid response, high sensitivity and specificity, portability, label-free detection, and cost-effectiveness. As a result, this diagnostic approach possesses suitable features to develop point‐of‐care (POC) diagnostics and monitoring technologies. In this study, for the first time, an optical biosensor chip was developed and analysed using a localised surface plasmon resonance (LSPR) optical biosensing technique to monitor biomolecular interactions between mycolic acid TB antigen and anti-mycobacterium tuberculosis antibody. Mycolic acid was successfully immobilised on a gold-coated biosensor chip and allowed to react with an anti-mycobacterium tuberculosis antibody. To enhance the detection signal from biomolecular binding events, AuNPs were used and successfully bioconjugated with goat anti-rabbit IgG H&L secondary antibody and characterised using ultraviolet-visible (UV-vis) spectroscopy and subsequently introduced on the biosensing layer. Scanning electron microscopy (SEM) and energy-dispersive x-ray (EDX) spectroscopy were used to characterise the biosensing surface. The optimised biosensor chip was analysed using a custom-built biosensing transmission spectroscopy setup to perform LSPR biosensing. From our findings, it was realised that mycolic acid was successfully immobilised on the biosensing surface and made it possible to capture anti-mycobacterium tuberculosis antibodies. The LSPR optical biosensing technique was indeed successful in the detection of anti-mycobacterium tuberculosis antibodies.