Researchers at MIT have developed a new way to measure the mass of individual particles using tiny superparamagnetic beads, a technology that will hopefully lead to cheap and portable point-of-care diagnostic devices. The trick relies on using an oscillating magnetic field to make individual beads resonate . The frequency of the field that makes a bead resonate the most is proportional to the mass of the bead.
The team used magnetic walls within magnetic tracks to resonate the beads. By attaching antibodies to the beads that attract specific pathogens, they can measure the difference between the resonant frequency of the bead with and without the new particle and therefore derive its mass.
From MIT’s news room:
An operational device using this new approach would consist of a small reservoir above the tracks, where the liquid containing the magnetic beads and the biological sample would be placed.
Rather than pumping the fluid and the particles through channels, as in today’s microfluidic devices, the particles would be controlled entirely through changes in applied magnetic fields. By controlling the directions of magnetic fields in closely spaced adjacent regions, the researchers create tiny areas with extremely strong magnetic fields, called magnetic domain walls, whose position can be shifted along the track.
Besides being potentially quicker and requiring a far smaller biological sample to produce a result, such a device would be more flexible than existing chip-based biomedical tests, the researchers say. While most such devices are specifically designed to detect one particular kind of protein or disease agent, this new device could be used for a wide variety of different tests, simply by inserting a fresh batch of fluid containing beads coated with the appropriate reactant. After the test, the material could be flushed out, and the same chip used for a completely different test by inserting a different type of magnetic beads.