While we can make big objects float (think of maglev trains), paradoxically scientists have found it much trickier to make small, and especially living, things levitate. But now a group of researchers have managed to do just that, and they believe the technique could be useful in sorting healthy cells from cancerous ones. The study is published in the Proceedings of the National Academy of Sciences.    

The team of scientists from Stanford University has shown that they can use magnetic fields to levitate individual cells. While this might not be the first time that researchers have managed to make living things float – others have managed it with strawberries, insects, and even live frogs – this new research was able to demonstrate that “both eukaryotic and prokaryotic cells can be levitated and that each cell has a unique levitation profile.” If you're not familiar with those terms, prokaryotes are single-celled organisms like bacteria, and eukaryotes are organisms made up of more complex cells, like plants and animals. 

^{Levitating frog from the Nijmegen High Field Magnet Laboratory, which won the Ig Nobel Prize in 2000. GIF made from YouTube video by Graham McLeod}

They were able to show that each cell type will float at a different height depending on its density. In a series of experiments, they illustrated that just a few minutes of exposure to the magnets caused a mix of different cancer cells to separate into different layers. In addition to this, as cells change density when they die, the researchers were able to watch as individual breast cancer cells dropped one by one as they were killed by acid.   

The scientists managed this floating trick by soaking the cells in a magnetic fluid and then suspending them between two magnetic plates. Such fine control of small objects wasn’t thought possible before as researchers struggled to manipulate magnets on such a minute scale. This new technique makes it possible to rapidly differentiate between healthy and cancerous cells, and even assess how bacteria and yeast respond to various compounds of interest in real time.

Whilst watching cells such as bacteria and fungi respond to the different drugs, they noted that something else interesting happened – the cells didn’t die and drop at the same rate. According to the authors, this could hint at the individual cell's ability to withstand these pressures, and how certain cells gain resistance.  

Not only this, but it could allow researchers to distinguish between cells that are currently thought to be the same, or homogenous, by picking up on these subtle differences in density. And all without the need of adding any special biomarkers or antibodies, meaning that it could potentially form a diagnostic test that could be carried out in resource-poor settings. They even plan on looking into whether the results can be observed using a lens attached to the humble iPhone.