A team of researchers at the USC Viterbi School of Engineering in the US have developed a prototype for a portable device capable of early-stage malaria detection.
This device could play a key role in solving the global malaria crisis as malaria therapeutics are most effective after early-stage diagnosis.
The optical diagnostics system (PODS ) prototype was developed by USC Viterbi engineers Andrea Armani, Samantha McBirney, Dongyu Chen, and Alexis Scholtz. It can detect a by-product generated by all species of the malaria parasite and offers the prospect of rapid screening for all malaria strains.
The PODS instrument has been designed to solve challenges limiting current systems. The researchers aimed to minimise the system’s size, weight and power requirements without sacrificing performance.
The current prototype weighs under 10bs, is 12 by 10 inches in size, and can be battery-powered for eight hours. It also requires minimal sample processing and handling and does not require secondary chemicals. This makes the device particularly suited to use in developing countries, where the malaria disease burden is highest.
“Malaria primarily impacts low-resource environments where supply chain management is difficult and access to power can be unreliable,” said Armani. “Therefore, an effective malaria diagnostic must be independent of these.”
The device can analyse an unprocessed, whole blood sample in 10-15 minutes and only requires five to seven drops of blood to provide a diagnosis.
The technology relies on the detection of heme, a byproduct produced by the malarial parasite as it digests haemoglobin.
Lead author and PODS co-inventor Samantha McBirney said: “While heme is highly toxic to both the parasite and its host, the parasite has figured out a ‘loophole’ around this by aggregating heme into an insoluble nanocrystal known as hemozoin. Unlike all other naturally-occurring materials in the blood, hemozoin is magnetic.”
Hemozoin works as a good indicator of infection because the amount of hemozoin in the blood is directly related to how far the malaria infection has progressed. However, detecting hemozoin nanoparticles in blood can be challenging because of the many other blood components interfering with the measurement. To overcome this problem, the researchers used the magnetic behaviour of the nanoparticles to inspire the diagnostic design.
PODS has three primary components: a laser, a light detector and a magnet. A sample of blood can be placed between the laser and the detector and the amount of light that makes it to the detector decreases as the blood blocks it. If hemozoin is present then less light shines through.
However, hemozoin at low concentrations can be hard to detect and different blood samples absorb light differently. The PODS device tackles this by taking two measurements: one with the nanoparticles and one without the nanoparticles.
It is possible to manipulate the hemozoin particles within a test tube by using a magnet and they can be moved in and out of the laser beam. This allows a single sample to perform two measurements, and makes every diagnosis personalised.
The device has been designed using inexpensive, off-the-shelf components and does not require reagents so all parts are readily accessible and easily replaced.
The researchers are currently working on the next iteration of the device, with the aim of reducing the sample volume to one or two drops of blood. They also want the device to be able to operate for 30 hours with an external battery pack or be hand-powered.