Microfluidics as a Novel Technique for Tuberculosis: From Diagnostics to Drug Discovery

Abstract

Tuberculosis (TB) remains a global healthcare crisis, with an estimated 5.8 million new cases and 1.5 million deaths in 2020. TB is caused by infection with the major human pathogen Mycobacterium tuberculosis, which is difficult to rapidly diagnose and treat. There is an urgent need for new methods of diagnosis, sufficient in vitro models that capably mimic all physiological conditions of the infection, and high-throughput drug screening platforms. Microfluidic-based techniques provide single-cell analysis which reduces experimental time and the cost of reagents, and have been extremely useful for gaining insight into monitoring microorganisms. This review outlines the field of microfluidics and discusses the use of this novel technique so far in M. tuberculosis diagnostics, research methods, and drug discovery platforms. The practices of microfluidics have promising future applications for diagnosing and treating TB.

Keywords: Mycobacterium; antibiotics; antimicrobial resistance; bioengineered models; diagnostics; drug discovery; microfluidics; single-cell analysis; tuberculosis.

Figure 4

(A) Stacks microfluidic platform for analysing soluble signalling. The top layer contains the granuloma model in collagen and the bottom layer contains human vasculature endothelial cells on a Matrigel layer. Soluble factor signalling can be studied from the granuloma microenvironment [164]. (B) Schematic of DAC system. A 24-well plate fabricated from poly(methyl methacrylate) (PMMA) with a top view of an individual well (diameter of 12.4 mm and height of 12 mm). The disc-shaped channel (300 μm depth) is filled with agarose and mycobacteria. An inverted microscope is placed underneath for time-lapse imaging [159]. Created on BioRender.com, accessed on 26 October 2021.

Figure 1

Tuberculous granuloma. Encapsulated Mycobacterium tuberculosis surrounded by immune cells, creating a hypoxic, nutrient-deprived, and nitric oxide environment. Adapted from “Granuloma”, by BioRender.com (2020). Retrieved from https://app.biorender.com/biorender-templates, accessed on 27 September 2021.

Figure 2

Water-in-oil droplet-generation microfluidics. (A) Production of water-in-oil droplets using a flow-focusing design. The dispersed phase is squeezed by two counter-streaming flows of the carrier phase, forcing drops to form and detach. (B) Droplet generation using T-junction, flow-focusing geometry and step emulsification. (C) Graph showing that droplet size decreases, and frequency of formation increases with increasing oil flow rate. Figures created on Biorender.com, accessed on 9 November 2021.

Figure 3

Schematic illustration of droplet system coupled to an Integrated Comprehensive Droplet Digital Detection. Flow-focusing microfluidic chip geometry producing encapsulated mycobacteria in droplets. Figure created on Biorender.com, accessed on 26 October 2021.