Growth of Nerve Fiber Directed

Laser-driven spinning microparticles can direct the growth of nerve fiber. This discovery that could enable the growth of neuronal networks on a chip and improve methods for treating spinal or brain injuries.

The study, which appeared in the January issue of Nature Photonics, is based on a hypothesis by Samarendra Mohanty, an assistant professor of physics at the University of Texas at Arlington. He proposed that neurons can respond to physical cues as well as chemical ones. His work led the University of California, Irvine, team of professor Michael Berns to test “micromotors” in guiding neurons. Berns’ group is the first to demonstrate that neurons can be turned in a controlled manner by microfluidic flow, directing them to turn right or left.

In the experiment, spinning microparticles created the flow, which could be generated in the body by a tube carrying fluids. The UC Irvine scientists used laser tweezers to trap and spin a birefringent particle (calcite or vaterite) near axonal growth cones, which are the tips of neurons where connections are made with other neurons or cells. The same laser causes rotation of the particle, which creates the flow, Mohanty said.

In lab experiments, the new method successfully turned the growing axon in a new direction up to 42 percent of the time. The technique may have the potential for use in vivo to direct regenerating axons to mediate brain and spinal cord repair. Additionally, the experiments give insight into the effect of shear or lateral forces on neuron growth. That knowledge may apply to other forms of cell growth also.

Mohanty’s lab now is developing a method that allows long-range optical guidance of neurons with 100 percent efficacy without using additional external objects.

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