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New test strip preserves clues that blood tests may overlook

Armed services blood program Photo Margrette Dorn

The new synthetic paper for finger prick blood tests, developed at KTH Royal Institute of Technology, could provide accurate point-of-care diagnostics for cancer, COVID-19 and other serious diseases.

The innovation enables detection of important biomarker proteins that might otherwise evade the blood plasma screening process, reports David Callahan at KTH.

Recovered at least 10 percent more proteins

Wouter van der Wijngaart, Professor in micro and nanosystems at KTH, says that the synthetic test paper recovered at least 10 percent more proteins from plasma than is possible with current filtering methods. The best current filters enable recovery of 70 percent of proteins, he says.

“This could in theory be used for any type of protein, such as antibodies,” he says. “One could easily imagine adding a test line for COVID-19 antibodies in the plasma strip.”

The surface makes the difference

The difference starts with the surface of the filter, Wouter van der Wijngaart says. “Blood filters not only keep out blood cells, but they also bind protein in the blood. This is a problem because filters have a large internal surface, hence a lot of binding sites for protein.”

By contrast, the synthetic paper’s relatively low internal surface area – composed of a micro-scale scaffold of interlocked pillars – binds comparatively little protein, reports David Callahan.

The filter’s design consists of a square area that contains a blood clotting agent, adjoined by a channel which collects the plasma. Blood is dropped on the square area, where the clotting agent forces the blood to clot, and the blood cells become stuck there. The plasma flows into the channel through capillary action – a natural phenomenon resulting from the interplay between two kinds of forces, cohesion and adhesion (the same force that enables water to flow into a plant through its roots).

The plasma extractor could be integrated with conventional testing, according to van der Wijngaart. Because they rely on the natural force of capillary action, lateral-flow test strips are self-contained and autonomous. The unit production cost of the material is only about 2 to 4 times that in commercial tests, the researchers estimate.

The results were reported in ACS Publications, Analytical Chemistry.

Source: David Callahan/KTH

Image caption: KTH researchers have developed a finger-prick blood test strip for filtering blood plasma recovers 10 percent more proteins than existing methods. Photographer: Margrette Dorn