The “missing millions” are the estimated three million undiagnosed cases of tuberculosis (TB) worldwide each year, according to the World Health Organization. A cutting-edge study has tested a diagnostic device that uses dielectrophoretic and has the potential to improve the detection and treatment of tuberculosis in underserved, high-endemic areas. Global targets for reducing the burden of tuberculosis will be met by providing diagnostics to the most in need patients. The findings of the study are published in The Journal of Molecular Diagnostics.
The opportunity to prioritize the development of a low-cost, fast, accurate, and portable TB diagnostic test for analyzing sputum samples for Mycobacterium tuberculosis (Mtb) from suspected TB patients presented itself thanks to a one-of-a-kind collaboration between the TB research group at St. George’s University of London, the Institute for Infection and Immunity, and QuantuMDx, a UK-based medical technology company.
“The global burden of TB is not improving,” lead investigator Philip D. Butcher, Ph.D., St. George’s University of London, stated. Despite its infectious nature, it is extremely treatable. To reach the “missing millions,” however, affordable diagnostics that are suitable for implementation at the point of care are required. We realized that novel technologies may provide an answer because our TB research group at St. George’s has long recognized the global need for improved TB diagnostics. By working together on a new chip-based technology that uses dielectrophoresis to selectively isolate Mtb bacilli from sputum samples, we saw an opportunity.”
“The CAPTURE-XT technology is truly revolutionary, with applications ranging from sepsis to oncology (circulating tumor cells). This application in Mtb is absolutely special because of its ultra-low cost and ultra-high sensitivity, which would significantly improve fair access to accurate diagnoses for hundreds of millions of people.”
Jonathan O’Halloran, Ph.D., founder and Chief Executive Officer of QuantuMDx Group. Ltd.
The researchers talk about a prototype QuantuMDx microfluidic lab-on-a-chip system called CAPTURE-XT that can process solubilized sputum from people who think they might have TB, capture Mtb bacilli for visual analysis instead of smear microscopy, and provide a purified sample for molecular confirmation by quantitative PCR (qPCR) and, eventually, genotypic drug-susceptibility analysis.
Dielectrophoretic, a little-known method that can be adjusted to selectively attract or repel particular cells or particles based on their dielectric properties, is the foundation of the CAPTURE-XT technology. While the rest of the sputum is washed away, in this instance, only the M. tuberculosis bacteria that are responsible for tuberculosis are specifically captured and concentrated.
The performance of the prototype was evaluated through a blinded screening of 100 characterized and biobanked sputum samples provided by the Foundation for Innovative New Diagnostics (FIND) following optimization using a panel of 50 characterized sputum samples.
Video of dielectrophoresis using the CAPTURE-XT chip to capture and release Mycobacterium tuberculosis bacteria, which were seen by fluorescence microscopy as white, fluorescent spots on the edges of the electrodes. Bacterial particles gradually accumulate along the edges of the electrodes as soluble sputum flows from right to left across the chip’s electrodes. The electrodes to the left of the chip fill up with bacteria as more sputum passes over them, providing a direct visual count of the bacteria in the sputum sample. 47 seconds after the dielectrophoretic current is released, all of the bacteria are released in a single pulse, enriching the outflow and making molecular method detection more sensitive. Credit: Moore et al. The Journal of Molecular Diagnostics.
According to the Journal of Molecular Diagnostics, 100% of smear-negative samples and 87% of smear-positive samples were consistent with the culture diagnosis. The high-burden sample concordance for all smear-positive samples was 100%. Based on these findings, the technology has the potential to provide a powerful sample preparation tool that could serve as a front-end platform for improved molecular detection. This adaptable instrument could also be used as a visual diagnostic for detection, possibly in conjunction with bacterial identification for inexpensive screening.
“The CAPTURE-XT technology is truly ground-breaking and will have an impact on a wide range of diseases, from sepsis to oncology (circulating tumor cells).” According to Jonathan O’Halloran, Ph.D., founder and Chief Executive Officer of QuantuMDx Group, “This application in MTB is truly exceptional because its ultra-low cost and ultra-high sensitivity will profoundly improve equitable access to quality diagnoses for hundreds of millions of people.” Ltd. states, “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 or microscopic methods, which typically have low detection rates and require training laboratory staff, at molecular-like sensitivities and at a fraction of the price.” These methods typically have low detection rates and require training for laboratory staff. Furthermore, the possibilities are almost endless when used as a front-end for downstream cellular, protein, and molecular devices.”
“Collaboration between university-based academic researchers and biotechnology industry scientists presents a way forward to develop new approaches for some of the world’s greatest healthcare challenges, such as tuberculosis,” Professor Butcher said in his conclusion. By making case finding easier, this brand-new chip-based technology has the potential to both bring diagnostics to patients who require them and stop the disease from spreading further.
“Tuberculosis is one of the oldest challenges faced in human healthcare,” stated co-author Heather Murton, Ph.D., LEX Diagnostics, Melbourn, UK, formerly of QuantuMDx Group Ltd. It is exciting to see a seemingly abstract physics principle successfully applied to a neglected disease area. This technology has the potential to meet the expectations for a mobile TB diagnostic.”
TB is the 13th leading cause of death worldwide, and prior to COVID-19, it was the leading infectious disease-related cause of death, surpassing malaria and HIV. It kills 1.4 million people annually and infects 10 million people worldwide, 230,000 of whom are children.
To address drug resistance and diagnose cases with a low bacterial burden, additional drug susceptibility testing and diagnostics with increased sensitivity are required.
More information: A Novel Microfluidic Dielectrophoresis Technology to Enable Rapid Diagnosis of Mycobacteria tuberculosis in Clinical Samples, Journal of Molecular Diagnostics (2023). DOI: 10.1016/j.jmoldx.2023.04.005
