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Bloodless malaria test passes first test in humans

23 Jun 2015

A new laser test that can detect malaria in seconds with a simple skin scan is the first in-human device to diagnose the disease without drawing blood.

The device works by sending a safe laser pulse through the skin to a blood vessel. Here, if present, tiny parts of malaria parasites (called hemozoin) absorb the laser light. This causes them to instantly heat up and produce a microscopic vapour ‘nanobubble’. When this transient vapour bubble bursts, it produces an acoustic ‘pop’ which is detected through the skin by a sensor, indicating the presence of malaria.

The fast, non-invasive test can detect malaria in both humans and mosquitoes. It has advantages over current techniques because it does not depend on blood sampling, reagents, facilities or trained personnel. The simplicity – it can be operated by non-medical personnel – and sensitivity of the test mean it could be a low-cost, safe and universal tool for clinical and field diagnoses.

The results come from a study involving a multidisciplinary, international team of researchers and engineers from The Gambia (Medical Research Council Unit, The Gambia), Lithuania, the United Kingdom and the United States, led by Dr Dmitri Lapotko, Director of the Nanobubble Lab at the Department of BioSciences at Rice University in the US.

The study, published in Emerging Infectious Diseases, involved using the device on a patient with confirmed malaria and in non-infected people as controls to assess the technical and medical feasibility of using the technique for malaria diagnosis and screening.

The device is made up of a pulsed laser and integrated probe which are scanned across the skin. The probe contains an optical fibre and an acoustic sensor. In response to each laser pulse, the probe detects an acoustic pulse and generates an output electrical signal as an acoustic trace. The team found that wrist and ear lobe veins were the best location for the test.

Acoustic traces from the wrist of the malaria patient showed an acoustic pattern similar to that of the hemozoin-positive samples tested in the lab. The traces had much higher amplitudes than those obtained from a healthy volunteer with a similar skin tone. Similar results from different body locations validated the successful detection of malarial infection by the hemozoin-generated vapour nanobubble (H-VNB) method.

Dr Dmitri Lapotko, who has led the development of the diagnostic device, said: “While we use a laser pulse to explode parts of the parasites inside infected cells, these tiny explosions are absolutely safe, as well as the whole diagnostic procedure, which takes seconds and is as simple as measuring the body temperature.”

Professor Umberto D’Alessandro, Director of MRC Unit, The Gambia and Professor of Epidemiology at the London School of Hygiene and Tropical Medicine in the UK, said: “This completely new diagnostic approach has the potential to play a major role in malaria elimination as it could be used to identify and treat infected individuals. We have provided malaria expertise to Dr Lapotko’s team and we are contributing to the formulation of the development plans. If everything goes as planned, the test could be evaluated in The Gambia in about 18 months from now.”

The results provide a proof-of-principle for the H-VNB technique. The next step is to optimise the prototype with a malaria-specific laser for better sensitivity. The prototype will be evaluated in large-scale human studies in clinical and field settings in malaria-endemic countries.

Article citation: Lukianova-Hleb E, Bezek S, Szigeti R, Khodarev A, Kelley T, Hurrell A, et al. Transdermal diagnosis of malaria using vapour nanobubbles. Emerg Infect Dis. 2015 http://dx.doi.org/10.3201/eid2107.150089

Find out more about malaria research at MRC Unit, The Gambia: www.mrc.gm

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