From ExtremeTech:
In the brain, the complex
circuits behind our cognition largely construct themselves. In a dish or
on a chip however, the normal meaningful cues are missing, and any
attempts to grow predefined circuits from neurons have largely met with
failure. A new technique, dubbed magnetogenetics, has now
provided a way to create these neural circuits by combining magnetic
manipulation with the cell's own machinery for stabilizing new growth
and extensions.
The technique works by making use of the cell's
ability to target a protein, known as Rac-GTPase, which promotes the
formation and stabilization of new branches. The researchers used 500nm
(0.0005mm) magnetic beads that have been modified so they can hook up to
these protein machines soon after they come off the presses. They can
then be magnetically acquired, and then moved to the desired locations
using a precisely controlled force. In order to see what they are doing,
they also attached fluorescent beacons to the beads.
Other researchers had
previously tried mechanically pulling on the cells with microactuators,
and while impressive growth could be obtained, fine control was
impossible. Other techniques using laser tweezers to pull on subcellular
transparent beads, or even the cell directly also had some successes,
but the level of light power necessary to do this is typically damaging
to the cells. (See: Manipulating nanoparticles with an electron tractor beam.) To
grow neurons on semiconductors, adhesion molecules have typically been
pre-patterned along traces for the neurons to follow. When these
molecules invariably degraded over time, the neuron was left without any
natural supporting structure. By using a machine that nucleates the
cellular endoskeleton directly, new processes can be drawn out in a more
natural way that the cell can adapt to.
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