Place an infected sample of blood in a powerful magnetic field and crystals produced by malaria parasites line up like toy soldiers, allowing them to be easily identified.
The new technique from the Bulgarian team detects a byproduct that malaria parasites produce in the blood when they break down molecules of the blood pigment, haemoglobin.
This process creates tiny cylindrical crystals of a substance called hemozoin, which turns out to have remarkable properties. The most significant of these is its iron content makes hemozoin magnetic.
Various research groups have noted that placing infected blood in a magnetic field causes the crystals to line up. However, this effect is countered by the constant buffeting of thermal forces which tend to disorder the sample.
That gave Butykai and co an idea. Instead of a static field, these guys put their sample in a rotating field which causes the crystals to spin, like tiny magnetic spinning tops. Since their magnetic axis is along the length of the cylinder, they spin around this long axis, making the crystals stand up in the field like toy soldiers.
This alignment is much more stable against thermal forces and gives the blood unusual optical properties since it allows polarised light to travel more easily along one direction than in the perpendicular direction.
In addition, Butykai and co have found that the hemozoin soldiers interact more readily with some frequencies than others, producing a unique optical signature. It’s this that can be used to spot malaria parasites in blood, serum or plasma.