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For Remote-Control Cells, Just Add Magnets

Magnetic particles turn cell signals on and off
cells under magnet



Courtesy of Donald Ingber and Kristin Johnson

A new study suggests that to meld living cells with the digital world, think of them as you would a refrigerator door—a handy place to stick magnets.

Researchers report in Nature Nanotechnology that they triggered immune system cells to begin a biochemical process that produces histamine (the chemical responsible for allergic responses) by dusting them with iron particles and applying a magnetic field.

They say the technique could lead to lighter weight, lower power biosensors for detecting pathogens, or novel ways of delivering drugs to specific parts of the body—if not the healing powers sometimes attributed to magnetism. "The idea was, could you actually have an interface with living cells that would be analogous to a machine interface or a computer interface," says cell biologist Donald Ingber of Harvard Medical School and Children's Hospital Boston.

Cells are studded with a variety of receptor proteins that activate when certain molecules latch onto them, triggering a cascade of biochemical events inside the cells that result in actions such as the secretion of hormones or destruction of pathogens.

In order to send such a signal, receptors often must also knock into one another. Ingber and his colleagues sought to magnetically induce this jostling by coating particles of iron oxide with dinitrophenyl (DNP) molecules that attach to the receptors on histamine-producing mast cells.

The 30-nanometer-wide iron oxide beads (about the size of a virus) were superparamagnetic, or capable of repeatedly becoming magnetic in the presence of a true magnet. When magnetized, the beads would attract one another, forcing the receptors to huddle and activate.

The researchers report that when they switched on an electromagnet near the coated cells, there was a spike in the calcium levels inside them, which is the first step in the histamine secretion process. The spike ended when they switched off the magnet. The results demonstrate "unprecedented control" over individual cell receptors using an electromagnetic field, University of Pennsylvania bioengineer Christopher Chen wrote in an editorial accompanying the study.

Ingber envisions one day using a similar trick to create pacemaker-like systems for regulating insulin levels in the blood or to deliver antidotes to soldiers exposed to chemical or biological weapons. But first, he notes, researchers will have to see if they can apply the process to other cells and get the desired effects.

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