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Microfluidic Chip Aids Tuberculosis Diagnosis

Conn Hastings |

Researchers at the University of London have collaborated with QuantuMDx, a medtech company based in the UK, to develop a microfluidic diagnostic device for tuberculosis. The CAPTURE-XT chip is designed to concentrate and purify Mycobacterium tuberculosis from suspected tuberculosis patients, particularly in areas that lack access to routine diagnostic technologies. The chip uses dielectrophoresis to capture the bacteria based on their dielectric properties, whereas other bacteria and impurities in the sputum sample are washed away. The captured bacteria can be assessed visually, providing a simple yes/no diagnosis, and the purified sample can also be characterized in a lab for more in-depth analysis.

The World Health Organization estimates that there are approximately three million people who contract tuberculosis each year but who are undiagnosed. Many such patients live in low-resource areas where access to diagnostic technologies is not reliable. There is a clear need for inexpensive diagnostic devices that can detect the causative bacteria behind tuberculosis.

Representative sputum samples from: A: smear negative, but culture positive (very low bacillary load); B: smear positive grade +1; C: smear positive grade 2+. A correlation between smear positive grading of the sputum sample and the visual count of captured particles of bacilli (indicated by arrows) is seen.

To address this, these researchers have developed a microfluidic chip that can capture and concentrate these bacteria from sputum samples. The test works on the basis of dielectrophoresis, which essentially means applying an electric field to particles or cells, causing them to become polarized. However, the electric field is non-homogenous, resulting in movement in the polarized particle. The dielectric properties of Mycobacterium tuberculosis mean that the chip can use dielectrophoresis to selectively concentrate small numbers of the bacterial cells on the chip electrodes, allowing other bacteria and impurities to be washed away.

The bacteria that are concentrated on the electrodes can be viewed through a microscope, allowing an inexpensive and simple visual identification that is suitable for use in low-resource regions. However, if lab equipment is available, then the chip can act as a simple method to prepare and purify samples before performing more advanced tests, such as PCR, to better characterize the infective bacteria.

“The CAPTURE-XT® technology is truly revolutionary and will have an impact in many different diseases from sepsis to oncology (circulating tumor cells),” said Jonathan O’Halloran, CEO at QuantuMDx. “This application in Mycobacterium tuberculosis is truly exceptional as its ultra-low cost and ultra-high sensitivity will profoundly improve equitable access to quality diagnoses for hundreds of millions of people. This chip-based technology exploits the physiological property of the TB bacteria to be specifically collected onto the device so that small numbers can be visualized on the chip electrodes and act as a visual readout to replace the lab-based sputum smear/microscopic methods, which typically have low detection rates and require training laboratory staff, at molecular-like sensitivities and at a fraction of the price. Moreover, when used as a front-end to downstream cellular, protein, and molecular devices, the possibilities are almost limitless.”

Study in Journal of Molecular Diagnostics: A Novel Microfluidic Dielectrophoresis Technology to Enable Rapid Diagnosis of Mycobacteria tuberculosis in Clinical Samples

Via: Elsevier

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