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A team of scientists at the Massachusetts Institute of Technology, Cambridge, have discovered a way to detect early-stage malarial infection of blood cells by measuring changes in the infected cells’ electrical properties. The researchers built an experimental microfluidic device that uses a single drop of blood, streaming it across an electrode that measures a signal differentiating infected cells from uninfected cells. Their work is a first step toward a field-ready, low-cost, portable malaria detection device.

When the malaria parasite Plasmodium falciparum infects a red blood cell, the cell becomes more magnetic and more rigid, properties that can be detected in a rapid-diagnostic device. However, these changes are hard to detect before the parasite matures.

So the researchers chose to use electrical impedance as a diagnostic signal. Many infections, including malaria, alter a cell’s impedance, or electrical resistance across the cell membrane. They built a microfluidic cell-counting device that could measure the magnitude and phase of the electrical impedance of individual cells. The difficulty involved optimizing the electronics to allow very accurate measurements of impedance for each cell as it passes by, to minimize interfering electric signals from the substrate the blood flows over and prevent the cells from sticking to one another.

By mathematically combining the measures into an index called delta, the differences between uninfected cells and the stages of infection became clear. This ability to discern the circulating parasite’s stage from a drop of blood opens the possibility of building a device that could be used to rapidly diagnose malarial infection in places where laboratories and skilled medical personnel are scarce.

They say that their goal is to create a postage stamp-sized device with integrated electronics that can detect if a person has malaria and at what stage. Similar diagnostics may be applicable to other infections and diseases.

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