Image created by Dr. Michael J. Miller
Nearly half the world’s population remains at risk of malaria, yet the availability of fast non-invasive diagnostics tests is still lacking. A new technology in development, called the Cytophone, offers a different approach.
“The World Health Organization (WHO) seeks to reduce malaria case incidence by at least 90% globally and to eliminate malaria from 35 countries by 2030, as compared to 2015,” explained Vladimir Zharov at the University of Arkansas for Medical Sciences and developer of the new technology. “The lack of an optimal diagnostic tool can be a major obstacle to reaching this goal.”
Unlike traditional tests, Cytophone — “cyto” meaning cells and “phone” referring to the device’s ability to listen to signals from cells — doesn’t require a blood sample. Instead, it uses a combination of lasers and ultrasound applied to the skin to detect red blood cells infected with malaria parasites.
“Cytophone could fill this gap and be global game changer,” said Zharov.
Modern technology to tackle an ancient disease
Even in an era of medical and technological advancements, malaria-related deaths continue to rise, with children and pregnant women most at risk. Africa carries a huge portion of this burden, representing over 90% of cases and deaths. The limitations of current diagnostic tests make controlling, managing, and eliminating this disease very challenging.
Polymerase chain reaction (PCR)-based tests are currently the most sensitive diagnostics, but it takes time and requires analysis by highly skilled staff in an advanced laboratory, making it difficult to implement widely in low to middle income countries.
This makes it vital to develop better tests that can be carried out onsite so treatment can begin. Two such tests are currently available: rapid diagnostic tests and microscopy, where a blood smear is examined under the microscope for parasites. But like PCR-based tests, they also require a blood sample.
“Rapid diagnostic tests rely on detecting antigens [specific proteins] produced in the parasite” explained epidemiologist Sunil Parikh of Yale School of Public Health and one of the study’s co-senior authors. These antigens serve as markers to indicate the presence of the parasite in the blood.
However, some strains of malaria parasites have evolved and no longer produce antigens the tests are designed to detect. “This makes some of the tests no longer effective for diagnosis,” said Parikh.
Listening to cells
To address these shortcomings, Parikh joined forces with Zharov, a bioengineer who had been working with Cytophone technology to identify circulating cancer cells in melanoma.
“Alexander Graham Bell, who invented the first telephone more than one century ago, also developed a photoacoustic wireless telephone called photophone using sunlight,” explained Zharov. “This inspired me to use a much more powerful laser light to develop Cytophone, which can ‘listen’ to the sound from single cells in blood flow.”
Malaria is caused by different species of the Plasmodium parasite,which invades red blood cells and feeds on haemoglobin — the protein responsible for transporting oxygen around our body.
During this process, the parasite produces a byproduct called hemozoin, an insoluble crystal that has specific physical and chemical properties that make it a useful target for detection.
Parikh explains that cells with hemozoin absorb more energy from the laser, heating them and causing them to expand and create sound waves. The device then detects these sound waves as distinct signals, identifying the presence of infected cells without the need for a blood sample. The study found this procedure was safe with no participants having any adverse reactions.
The researchers are uncertain about the cost of these devices but note that lasers have become more affordable. With minimal use of consumables, they believe the cost per malaria diagnosis could be manageable. If true, this innovation could be a game changer for millions.
A promising start
Trialling their device in collaboration with researchers in Cameroon, Cytophone detected malaria just as accurately as the point-of-care tests compared to PCR-based tests albeit in a small sample of 20 patients.
Taking this further, the team also wanted to know if Cytophone could detect falling levels of malaria parasites in the same group of 20 patients who were treated for malaria. Followed for about 30 days after treatment, signals of malaria detected by the Cytophone mirrored the decline in infection levels noted in microscopy and PCR-based tests.
“It is still early days, but we are very excited about these results,” said Parikh. “In areas where there is a lot of disease, this device could be used to test large numbers of people in short periods of time […] and action could be taken. In areas where malaria has been eliminated, or nearly eliminated, a test that does not need blood could also allow for screening of individuals to prevent the reintroduction of malaria in a location.”
More research is needed before this device becomes readily available. Moving forward, the researchers want to evaluate the device in a larger sample size to determine reproducibility, diagnostic performance in children, and to determine if it can detect low levels of malaria in asymptomatic individuals.
“Currently we are trying to apply a machine learning and artificial intelligence (AI) platforms for quick identification of disease-related signal fingerprints, which can dramatically increase the specificity for screening asymptomatic individuals at early disease stages,” explained Zharov.
As all species of Plasmodium produce hemozoin, the researchers are confident the Cytophone will be capable of detecting all of them — though further testing will ultimately confirm its capabilities.
The team recently finished another study in Cameroon to further evaluate how sensitive the device is and if it can detect these very low levels of malaria — they say they hope to share the results soon.
Although they expect the device to be specific for malaria, future research will aim to also confirm this and check that other infections do not cause similar signals that could be mistaken for malaria. Additionally, the researchers are working to optimize the device to quantify infection levels and hopefully be able to distinguish between different Plasmodium species.
Parikh strongly believes in the power and necessity of different disciplines working together towards a common goal. “I think the research demonstrates the promise of multidisciplinary collaboration. Our group consists of bioengineers and malaria researchers from both Cameroon and the U.S. Without significant contributions from all the partners, these results would not have been possible.”
Reference: Vladimir P. Zharov, and Sunil Parikh , et al., Noninvasive in vivo photoacoustic detection of malaria with Cytophone in Cameroon, Nature Communications (2024) DOI: 10.1038/s41467-024-53243-z
Abstract
Current malaria diagnostics are invasive, lack sensitivity, and rapid tests are plagued by deletions in target antigens. Here we introduce the Cytophone, an innovative photoacoustic flow cytometer platform with high-pulse-rate lasers and a focused ultrasound transducer array to noninvasively detect and identify malaria-infected red blood cells (iRBCs) using specific wave shapes, widths, and time delays generated from the absorbance of laser energy by hemozoin, a universal biomarker of malaria infection. In a population of Cameroonian adults with uncomplicated malaria, we assess our device for safety in a cross-sectional cohort (n = 10) and conduct a performance assessment in a longitudinal cohort (n = 20) followed for 30 ± 7 days after clearance of parasitemia. Longitudinal cytophone measurements are compared to point-of-care and molecular assays (n = 94). Cytophone is safe with 90% sensitivity, 69% specificity, and a receiver-operator-curve-area-under-the-curve (ROC-AUC) of 0.84, as compared to microscopy. ROC-AUCs of Cytophone, microscopy, and RDT compared to quantitative PCR are not statistically different from one another. The ability to noninvasively detect iRBCs in the bloodstream is a major advancement which offers the potential to rapidly identify both the large asymptomatic reservoir of infection, as well as diagnose symptomatic cases without the need for a blood sample.