It’s a weapon that fights malaria – a laser scan can give an accurate diagnosis in seconds, without breaking the skin, just like the fictional tricorder in Star Trek.
It works by pulsing energy into a vein in a person’s wrist or earlobe. The laser’s wavelength doesn’t harm human tissue, but is absorbed by hemozoin – waste crystals that are produced by the malaria parasite Plasmodium falciparum when it feeds on blood.
When the crystals absorb this energy, they warm the surrounding blood plasma, making it bubble. An oscilloscope placed on the skin alongside the laser senses these nanoscale bubbles when they start popping, detecting malaria infections in only 20 seconds.
“It’s the first true non-invasive diagnostic,” says Dmitri Lapotko of Rice University in Houston, Texas, whose team used the probe to correctly identify which person had malaria in a test of six individuals. They even managed to use the device to show whether dead mosquitoes were carrying the parasite.
Malaria threatens half the world’s population, killing 584,000 people in 2013. Existing tests for malaria are already quick, taking only 15 to 20 minutes to give a diagnosis, but they could be simpler. Blood has to be taken, the test has to be conducted by trained personnel to get reliable results, and extra chemical reagents must be used.
Mark Perkins of the Foundation for Innovative New Diagnostics, a non-profit organisation set up by the World Health Organization, estimates that the world spends around US$100 million annually on these reagents. “The pursuit of technologies that avoid these pitfalls, especially when as innovative as this one, is welcome,” he says.
Lapotko says that a single, battery-powered device the size of a shoebox would house everything associated with the small probe, with no other reagents, facilities or specialist personnel required. The team estimates that a single unit would cost around $15,000, but that this could test 200,000 people – potentially bringing the per-person cost of testing down from as much as 50 cents to under 8 cents.
The team is now preparing for trials in Africa. “The possibility of diagnosing a malaria infection with the device, without any blood-taking and with results available in seconds will provide a fantastic new tool for the control and eventual elimination of malaria,” says Umberto D’Alessandro of the UK Medical Research Council Unit in Gambia.
“We need to find out how the test performs in field conditions and its capability of identifying infections with low densities of parasites in the blood,” says D’Alessandro, who is helping to organise a trial.
However Perkins says further tweaks are needed before the probe can become a mainstream diagnostic. For example, it gives a more ambiguous result if a patient has a dark skin – a potentially huge pitfall given that children living in Africa account for the majority of malaria deaths. But Lapotko’s team is confident it can overcome this effect by switching to a different wavelength of laser.