Stanford Medicine scientists report the development of a new device that relies on electromagnetic levitation to help them gently sort living cells, with no need for physical contact.
The technique, which researchers call Electro-LEV, holds the potential for transforming how scientists and clinicians isolate and study cells, and may lead to novel cancer treatments by allowing the separation of cancer cells from healthy ones.
The innovation, described in a recent paper that appeared in the Proceedings of the National Academy of Sciences by assistant professor of radiology Gozde Durmus, PhD, and her former researcher Malavika Ramarao, could also lead to innovations in separating live cells from dead ones, with minimal stress to the samples.
Levitating Cells
Traditional cell-sorting methods rely on attaching fluorescent labels or antibodies, or using centrifuges and chemical treatments that can damage delicate cells.
Enter Electro-LEV, which works very differently by sorting cells based on their density and susceptibility to magnetic influence, which governs how cells will interact with magnetic fields. The result is more like “an invisible force” that directs their movement in an almost ghostly manner, as recently described by MIT News.
“In the clinical setting, you may have a very low-volume biopsy sample, and you want to look at certain cells and keep them viable for further genomic testing—that would be a perfect application for this technology,” Durmus recently said in a statement describing she and her colleagues’ novel approach.
From Simple Magnets to Smart Fields
The new Electro-LEV system builds on a simple magnetic levitation principle, which forms the basis of the system Durmus developed more than a decade ago. By as early as 2015, her lab demonstrated that almost any cell could be levitated in a carefully arranged magnetic field.
That occurs, Durmus recently explained, because “everything on Earth has some inherent magnetic properties.”
For the setup used in their recent experiments, a pair of small magnets comparable in size to a stick of chewing gum was placed north-to-north and south-to-south, with a narrow glass capillary positioned between them. This small glass fixture serves as a channel through which a paramagnetic solution flows, where opposing magnetic fields push and pull at cells within until each reaches its natural equilibrium point, occurring at the exact height where it should become suspended based on its density.
“The magnetic forces we work with are very small, around 0.4 Tesla,” Durmus explained. However, the fact that the magnets used in the setup are just a millimeter apart allows the creation of a very strong magnetic field gradient, or the rate at which the field strength changes over distance.
“That’s the trick,” Durmus explained.
By comparison, MRI machines used in hospitals generally operate at much higher field strengths—around 7 Tesla—although their magnets are spaced further apart, which results in much smaller gradients.
Fundamentally, by employing compact geometry in their system, the Electro-LEV offers Durmus and her team a precise level of control over each cell’s position.
Precision Through Electric Current
Improving significantly on her team’s earlier design, the new Electro-LEV introduces electromagnetic coils to both of its magnets. By adjusting the electrical current that runs through these coils, the team is able to tune the magnetic forces being generated in real-time.
Durmus says the new design allows them to “very precisely manipulate the cells to separate them further,” and that cells levitating at different heights can then be channeled into upper or lower outlets as they flow out of the device. That way, if cells weren’t being sorted correctly, a simple adjustment to the current offers a quick fix.
“Everything is under your control in real time, so it’s more user-friendly,” Durmus said.
Dead or Alive—And Beyond
During their experiments, a variety of different cells were tested with the Electro-LEV, ranging from breast and lung cancer cells to fibroblasts and even white blood cells. The team also conducted tests to gauge the device’s ability to remove dead cells from samples they worked with—an important step required for accurate RNA sequencing and stem cell therapies.
Dead cells absorb more paramagnetic solution, which makes them more dense and causes them to levitate lower in the device than living cells. By starting with cellular samples that were approaching death, but still showing signs of life, Electro-LEV was able to purify them to nearly 93% live cells.
Another intriguing finding reported by the team is that they discovered clusters of cancer cells responded faster to changes introduced with the magnetic fields than individual cells did. This, they say, could offer a novel means of detecting aggressive tumor clusters that scientists associate with metastasis, and Durmus says that levitation speed could be used as a gauge for monitoring such cancerous cell clusters.
Beyond merely sorting cancer cells, Durmus says that Electro-LEV could offer a wide range of applications that include organizing microbial communities, assembling artificially-grown organoids, or even guiding the work of microrobots.
“It’s a broad, versatile platform,” Durmus says, adding that she envisions the development of new applications that she and her team haven’t even considered yet.
Overall, by leveraging magnetism rather than mechanical manipulation, Durmus and her team’s work with Electro-LEV offers researchers a more gentle, easily tunable, and potentially revolutionary way to study and sort microscopic life through the novel application of cellular levitation.
Micah Hanks is the Editor-in-Chief and Co-Founder of The Debrief. A longtime reporter on science, defense, and technology with a focus on space and astronomy, he can be reached at micah@thedebrief.org. Follow him on X @MicahHanks, and at micahhanks.com.