A form of magnetic levitation can separate living and dead cells without altering or damaging them in any way. The process could be used for everything from drug discovery to tissue engineering.
Cells normally sink to the bottom of the fluid they are grown in. Gozde Durmus at Stanford University in California and her colleagues have developed a way of 鈥渓evitating鈥� them using magnetism.
鈥淓verything on Earth is magnetic,鈥� says Durmus. Her team puts cells in a fluid containing ions of the rare earth metal gadolinium, which is weakly magnetic, or paramagnetic. This form of gadolinium is non-toxic, and is injected into people to improve contrast in MRI images.
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The fluid is then put inside a glass tube with cheap simple magnets above and below it. The end result is an upward magnetic force on the cells that opposes gravity, so they float in the tube at a level that depends on their density.
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鈥淚t鈥檚 pretty simple to do,鈥� says Durmus, who聽first described on the technique in 2015 and has since been working on various applications. 鈥淎nybody can make these devices.鈥�
In her latest study, Durmus has shown that this method can be used to separate living and dead cells, because the density of cells increases after death. There are various ways of doing this already, such as spinning cells in a centrifuge, but these existing processes damage fragile cells.
Levitation is much gentler, says Durmus, and also allows researchers to observe the process as it happens, because dying cells start sinking straight away. 鈥淲e can pretty much watch cell death in real time,鈥� she says.
The technique could have all sorts of applications in medicine. For instance, we could add drugs and watch to see what levels are toxic to healthy cells, or required to kill cancerous cells. It also works with bacteria, says Durmus, so could help antibiotic development.
Tissue engineers are also working on ways of 鈥減rinting鈥� 3D organs. To do this, you need to separate healthy cells from dead and dying ones and other debris. 鈥淭his does it quickly,鈥� says Durmus.
A team at Harvard University is using the technique to identify illegal drugs. Other groups have levitated living animals聽in air using extremely strong magnets.
Reference: bioRxiv, DOI: 10.1101/2020.07.27.223917
