Bridging physics, engineering, and microbiology, researchers at MIT have measured the frequency at which red blood cells vibrate and have shown that those frequencies reflect the health of the cells. The research could lead to better medical diagnostics.

The work was performed in collaboration between MIT physicist Michael Feld and Subra Suresh, dean of MIT's school of engineering and a materials scientist. Feld heads MIT's Laser Biomedical Research Center, which has developed an imaging technique that can create three-dimensional images of living cells. Suresh's laboratory has conducted experiments to measure things like the stiffness of red blood cells infected by malaria parasites.

A red blood cell has electrical, chemical, and biological activity taking place inside it, which causes nanoscale vibrations at its surface. To measure the cells' vibrational frequencies, the researchers combined Feld's imaging technique with diffraction phase microscopy, in which a laser beam that passes through a cell rejoins a reference beam that does not, creating a distinctive interference pattern. To establish the connection between the cells' vibration and their health, the researchers used Feld's technique to create three-dimensional images of a malarial parasite inside a red blood cell. They also measured the levels of hemoglobin inside the cells during various stages of a malarial infection.

"This thing has never been done before," says Ares Rosakis, professor of aeronautics and mechanical engineering at the California Institute of Technology. "Scaling down optical techniques to [the nanoscale] level is extremely challenging." (Rosakis was not involved in the work, although one of his former graduate students was.)

Rosakis sees two uses for the new techniques. One is to improve computer models of cells, because Feld and Suresh's measurements are so much more accurate than previous measurements. The other is better diagnostics. The U.S. Centers for Disease Control (CDC) note that the main test for malaria currently does not work for acute malaria: it can recognize the disease only after the fact. Eventually, a technique like Feld and Suresh's could provide a way to detect malaria as it's happening. "Think of the future of a doctor or even an untrained technician having [the technology] built inside a commercial microscope and . . . instantaneously getting a reading on the state of the disease," Rosakis says.

Suresh notes that it was rare for mechanical engineers to work on cell biology, and rarer still to do it with physicists. But he and Feld "don't need to leave the building" to collaborate, he says.