Despite some advances in managing tuberculosis (TB), the disease has remained a worldwide health crisis. According to the Centers for Disease Control and Prevention, one third of the world’s population is infected with TB. In 2014, there were 1.5 million TB-related deaths worldwide.
Insufficient diagnostic tools are a big part of the problem. Late detection of TB, an infectious disease that generally attacks the lungs, increases the risk that the disease will be transmitted to others and that those suffering from it will have poor health outcomes. The most common tests take days to produce results, and can only detect TB if the disease has a reached a certain stage — and by that point, treatment becomes difficult.
Mark Reed and his lab are part of an effort that would dramatically change how the disease is diagnosed and treated. It’s a device that uses a method pioneered by Reed and his team that quickly separates TB cells from other cells in a sample. It’s sensitive enough to detect TB cells long before they become infectious, making the disease much easier to treat.
“We want something that can detect it many months before the disease actually goes full-blown, so you can do very early intervention,” Reed said.
Reed, the Harold Hodgkinson Professor of Electrical Engineering, is working in collaboration with British biotech firm QuantuMDx Group. It’s an ambitious endeavor that recently received a major boost with funding from the Bill & Melinda Gates Foundation.
The device takes advantage of a phenomenon known as dielectrophoresis (DEP), in which cells can be separated by an attracting or repelling force even when no charge is present. A sample containing the cells flows through a chip on the device and is subjected to a certain voltage that pulls the cells apart. The device traps the cells by employing frequency-dependent phenomena, and can be tuned to a certain frequency that allows it to capture one type of cell over another. The TB cells are then separated from the others in the sample and trapped.
Encouraged by the results, QuantuMDx has developed a number of prototypes currently being tested. Once it’s fully operational, the handheld device will process a patient’s sputum sample and be able to detect even a small number of TB cells. Reed figures that it’s a few years before the device will be ready for the market.
Reed began the project several years ago with Monika Weber, then a Ph.D. student in his lab. Weber is now leading a Boston-based start-up, and Reed has continued the project with Ph.D. students Shari Yosinski and Zak Kobos. Inside the lab in Becton Center, Reed, Yosinski and Kobos have been refining the technology to reach the high level of precision needed for the device to succeed.
“When you’re talking about such low limits of detection, if you miss a cell or two here and there — it will start to matter,” Yosinski said.
For safety reasons, they work with a simulant containing cells that act similar to those of TB (a QuantuMDx lab, outfitted with the necessary safety precautions, later tests the same technology using actual TB samples). Testing a sample, the researchers look at the computer screen connected to a sensor. A series of spikes show up on the computer screen, telling the story of the sample’s contents.
“Usually you get one spike per cell and the height of the spike is related to the width of the cell,” Kobos said. “You can infer what’s flowing in terms of the size, and then, because you know the bacteria population, you can infer what it actually is from the size and flow speed information.”
While QuantuMDx works on turning the technology into a product ready for the market, Reed and his lab continue to hone the system to increase its accuracy and speed.
“We want to be able to capture every cell, and make sure that we’re not missing any,” Yosinski said. “We want to know that we can process enough volume of fluids so that the test can actually give results within a reasonable amount of time. You don’t want this running for several hours before you get your test results.”
Time is crucial, especially in non-clinical settings where patients often leave after a certain amount of time. Reed’s goal for the device is to successfully detect and quantify the cells in 10 to 30 minutes. There are still tweaks they have to make, such as completing the microfluidic design to take the person’s sample and have it automatically go through the system. Some materials, they’ve found, cause the cells to stick instead of flowing through the channel to be processed. Although the cells didn’t stick when they were working on the technology in Reed’s lab, there were some complications with a prototype developed by QuantuMDx, due to variations in electronics.
“These things work at high frequencies,” he said, “so there’s a lot of electrical engineering and electrochemistry that goes into it to get the device working and able to get a more efficient design.”
The technology currently works on various pieces of lab equipment, but will eventually be miniaturized and put on a PC board. Making the device small and portable is key, since TB is a particular concern in resource-poor areas. Reed notes that well-equipped labs can use a microscope for optical detection, but that’s not much use when you’re going out into more remote areas. “Here, if a person gets tuberculosis, they can be treated in a hospital pretty quickly,” Reed said. That’s not always an option in other areas of the world.
“If you ever want to be in the field or do this at a low cost, you can’t bring your microscope around and do fluorescence imaging,” he said. “This device would literally be cellphone-sized and you can put a sample in there and it would then internally do the separation and then the count. Here, we can have a portable unit that you can take to a village and be able to test everybody and catch it early on before it starts to infect a person and spread.”
Source: Yale University