Magnetic levitation isn't anything new: you've probably seen frogs made to float and maybe even trains hovering above their rails. But now scientists have gained enough subtle control over such forces that they can be used to levitate single cells too.
A team at Stanford University has developed a new way of levitating cells, which you can see in action in the image above. They first soak the cells in a magnetic solution, before placing them between two neodymium magnets -- a process that takes just a few minutes. The cells then float at a height above the lower magnet which is related to their density -- the more mass per unit volume, the lower they sit. So far the team has used the technique to float different types of cancer cells, but it should work similarly well with any cell type -- say, the different types of blood cells, for instance. The results are published in PNAS.
Interestingly, the team has watched these single cells die -- killing off cancer cells with acid and E. coli with antibiotics -- and in the process observed them change density and hence position between the magnets. One sticking point is that it's not known how the soak in magnetic solution affects different cells' densities, so it's currently not easy to perform cell-to-cell comparisons. But, nonetheless, the team behind the work reckons that the technique could be used to test the effects of drugs and treatments on the physical properties of cells.