METHOD FOR GUIDING NERVE CELL GROWTH WITH LIGHT COULD LEAD TO TREATMENT OF SPINAL CORD INJURIES
25 November 2002 - University of Texas at Austin

Conceptual image of laser guidance: A neuron's key internal skeletal components are highlighted in red and green, and the laser's light is depicted at right. Actin molecules within the cell that permit growth are stained red.

By using low energy laser light placed at the edge of growing nerve cells (neurons), the investigators nudged neurons to extend their appendages in new directions.

“Small proteins within the cell that participate in growth would be attracted to this light, and would start drifting in the light’s general direction,” said Dr. Mark G. Raizen, one of the leaders of the research and a physics professor at The University of Texas at Austin.

The results will be published online next week by the Proceedings of the National Academies of Sciences. Josef Käs from the University of Leipzig in Germany was a co-lead investigator for the research.

Raizen and Käs, a former University of Texas at Austin faculty member, first became intrigued with the idea of manipulating neurons after hearing a lecture about the topic in early 2001. Researchers elsewhere were using “optical tweezers” to move living cells and other objects based on the same underlying principle: that objects with electrical properties are drawn into the center of a laser’s light beam. However, the stronger optical tweezers forced neurons and other objects to move against their will, often damaging the targets.

Using the kind of lasers that dermatologists work with to remove tattoos and blemishes, the investigators changed the general direction of growth for most neurons tested and increased their speed of growth up to six-fold. The researchers could even change the direction of growth by more than 90 degrees.

The cells were tested on a glass slide on the viewing surface of a microscope, and the laser light directed at them through the microscope’s viewing piece. The laser was directed at hand-like extensions of neurons called growth cones, which function to connect nerve cells throughout the body.

In the future, the laser guidance technique may lead to semiconductors that include nerve cell components, or neural networks that resemble structures in the brain, among other possibilities. As a step toward creating neural networks, Raizen is determining how to divide a stronger beam of laser light into sections that can simultaneously guide the growth of many neurons.

“By building this natural kind of neural network, we could understand how small networks of nerve cells function and learn,” he said, which may reveal insights into the more complex functioning of the human brain.

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