Tuberculosis (TB) is one of the main infectious diseases worldwide and accounts for many deaths. It is caused by Mycobacterium tuberculosis usually affecting the lungs of patients. Early diagnosis and treatment are essential to control the TB epidemic. Interferon-gamma (IFN-γ) is a cytokine that plays a part in the body’s immune response when fighting infection. Current conventional antibody-based TB sensing techniques which are commonly used include enzyme-linked immunosorbent assay (ELISA) and interferon-gamma release assays (IGRAs). However, these methods have major drawbacks, such as being time-consuming, low sensitivity, and inability to distinguish between the different stages of the TB disease. Several electrochemical biosensor systems have been reported for the detection of interferon-gamma with high sensitivity and selectivity. Microfluidic techniques coupled with multiplex analysis in regular format and as lab-on-chip platforms have also been reported for the detection of IFN-γ. This article is a review of the techniques for detection of interferon-gamma as a TB disease biomarker. The objective is to provide a concise assessment of the available IFN-γ detection techniques (including conventional assays, biosensors, microfluidics, and multiplex analysis) and their ability to distinguish the different stages of the TB disease.

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A cytochrome P450 3A4 (CYP3A4) based enzymatic biosensor was developed with the incorporation of a first-generation copper polypropyleneimine (CuPPI) metallodendrimer for the detection of anti-tuberculosis (anti-TB) drugs. The development of an electrochemical phenotype biosensor for this purpose is still vital since it aids in the ongoing fight against TB by determining metabolic profile. This allows TB treatment to be tailored on an individual patient basis, minimise adverse drug reactions and improve quality of life in TB patients. This simple biosensor was constructed via physical adsorption of CuPPI onto a gold electrode with subsequent electrostatic attachment of CYP3A4. The biosensor was successful in detecting all four first line anti-TB drugs i. e. isoniazid, ethambutol, pyrazinamide and rifampicin with limits of detection ranging from 0.02244 to 0.1072 nM in 0.1 M phosphate buffer. The developed biosensor was then applied towards "real samples" in the form of spiked synthetic urine and plasma. Calibration curves were carried out in the complex matrices, which were diluted with 0.1 M PB. These yielded good LOD in the range of ultra-low micromolar concentration i. e. 0.165-0.884 μM across all drugs. Recovery studies were also successful when detecting the real tablets in both plasma and urine with results ranging from 91.5 % to 108.5 %.

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