The researchers at USC Viterbi School of Engineering have developed a prototype for a portable instrument capable of detecting early-stage malaria. The related study of the has been published in the journal ACS Sensors. The instrument based on the detection of the malaria pigment, hemozoin (a byproduct generated by all species of the malaria parasite), resulting in a rapid screening for all malaria strains.
The portable optical diagnostics system (PODS) prototype is developed by USC Viterbi engineer Andrea Armani, the Ray Irani Chair in Engineering and Materials Science and colleagues.
According to the World Health Organization, over 216 million people were infected with malaria in 2016, and 445,000 individuals died from the disease. The key to reducing the number of deaths resulting from the disease is its early-stage diagnosis when malaria therapeutics are most effective.
The study is significant as although significant efforts and resources have been invested in developing antibody-based diagnostic methods for Plasmodium falciparum, a rapid and easy to use screening method capable of detecting all malaria strains has not been realized.
Presently, there are two standard ways for malaria diagnosis but both are subjected to some limitations. The first involves taking a blood sample from a person and observing them under the microscope for the red blood cells that have been infected with the malaria parasite. This method is manually intensive and dependent on the technician reading the blood smears as it involves counting of the cells. The second approach, known as the rapid diagnostic test (RDT), works in about 15 minutes. However, without refrigeration, RDTs can spoil like milk or eggs.
“Malaria primarily impacts low-resource environments where supply chain management is difficult and access to power can be unreliable. Therefore, an effective malaria diagnostic must be independent of these,” said corresponding author Andrea Armani.
Advantages of the Prototype:
- The instrument works on detection of a byproduct generated by all species of the malarial parasite and hence, through this, all strains of malaria can be detected.
- The prototype weighs fewer than 10 pounds, is 12 by 10 inches (the size of a large shoebox), and can be powered by a battery for eight hours.
- PODS was designed to require minimal sample processing and handling, as well as eliminate the need for secondary chemicals with strict storage requirements, this makes the device particularly suited to low-resource environments.
- can analyze an unprocessed, whole blood sample in 10-15 minutes with only 500 μL of blood (five to seven drops), it can achieve sensitivity levels needed for an early-stage diagnosis.
Detection of a few hemozoin nanoparticles in blood is extremely challenging because blood has many components that can interfere with the measurement. To overcome this problem, the researchers took inspiration from recent discoveries in personalized medicine and leveraged the magnetic behavior of the nanoparticles in their diagnostic design.
“With PODS, we can do rapid, broad population screening for malaria in low-resource environments. When combined with currently available therapeutics, this could represent a tipping point in the global fight against malaria,” says Armani.
“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,” says lead author, co-inventor, and recent biomedical engineering Ph.D. graduate, Samantha McBirney.
PODS has three primary components: a laser, a detector (to detect light), and a magnet. When a blood sample is placed between the laser and the detector, the amount of light that makes it to the detector decreases as the blood blocks it. If hemozoin is present, even less light shines through. At high concentrations even in blood, it is readily apparent if hemozoin is present because the nanocrystal is very good at blocking light.
By applying a magnet, it is possible to manipulate and move the hemozoin particles within a test tube around or move them in and out of the laser beam. In this way, a single sample can be used to perform two measurements, and every diagnosis is personalized. If hemozoin is present, even in minute concentrations, the signals change. On average, it takes between 10 to 15 minutes for the signal to stabilize, and a larger difference between the two measurements indicates that malaria has progressed farther.
“PODS operates on a very simple design concept. If there is hemozoin, then there must be malaria,” said Armani, “The challenging part was distinguishing the tiny hemozoin nanoparticles from everything else in the whole blood sample.”
The researchers employed a military design strategy, intentionally designing the device to try to use inexpensive, off-the-shelf components and not require any reagents. If a component fails, the engineers wanted to ensure that it was not necessary to seek out a custom supplier or a single source supplier.
“All the parts are readily accessible and easily replaced,” says McBirney.
“We are now working on the next generation of the device to improve its ruggedness and further reduce the sample volume to under 200 μL of blood,” said the researchers.
For more details click on the link: 10.1021/acssensors.8b00269