Malaria has several stages of development and once it passes the ring stage, the cells that it infects are noticeably stiffer and magnetically responsive. This fact has been used to diagnose the disease in humans, but while the Plasmodium is in its early development it remains elusive.
An MIT research team has developed a device that may end up being developed into a portable malaria detector. By running whole blood across an electrode, the device detects the impedance (resistance to an applied current) of each cell as it passes by. Since malaria infected cells have a slightly different electrical properties from their healthy counterparts, the detector can essentially spot the diseased cells in real-time.
Some details from MIT:
The challenge, however, involved optimizing the electronics to allow very accurate measurements of impedance for each cell as it passes by. The researchers had to minimize interfering electric signals from the substrate the blood flows over and prevent the cells from sticking to one another.
In tests of cells of four cell types — uninfected cells and infected cells at the ring, trophozoite and schizont stages — the device detected small differences in measures of magnitude and seemingly random differences in phase, but not quite enough to definitively differentiate among stages.
However, by mathematically combining the measures into an index called delta, the differences between uninfected cells and all three stages became clear. “It’s much more significant,” says corresponding author Ming Dao, a principal research scientist in the Nanomechanics Laboratory. “It’s a more holistic approach. By using all of the information we can measure, we can detect the differentiating signals much more clearly.”
“What’s really cool about this device is that it can actually differentiate between uninfected red blood cells and circulating ring infected red blood cells even though the parasite is still very small at this stage and the host cells have hardly been modified,” says Matthias Marti, an assistant professor of immunology and infectious diseases at the Harvard School of Public Health, who did not participate in the study.
Study in Lab on a Chip: Electric impedance microflow cytometry for characterization of cell disease states