For the first time ever, scientists were able to use nanotechnology to repair a damaged brain and restore vision. Work done by MIT investigators in a rodent model is being reported in the early online edition of the Proceedings of the National Academy of Sciences:
In the experiment on young and adult hamsters with severed neural pathways, the researchers injected the animals’ brains with a clear solution containing a self-assembling material made of fragments of proteins, the building blocks of the human body. These protein fragments are called peptides.
Shuguang Zhang, associate director of the CBE and one of the study’s co-authors, has been working on self-assembling peptides for a variety of applications since he discovered them by accident in 1991. Zhang found that placing certain peptides in a salt solution causes them to assemble into thin sheets of 99 percent water and 1 percent peptides. These sheets form a mesh or scaffold of tiny interwoven fibers. Neurons are able to grow through the nanofiber mesh, which is similar to that which normally exists in the extracellular space that holds tissues together.
The process does not involve growing new neurons, but creates an environment conducive for existing cells to regrow their long branchlike projections called axons, through which neurons form synaptic connections to communicate with other neurons. These projections were able to bridge the gap created when the neural pathway was cut and restore enough communication among cells to give the animals back useful vision within around six weeks. The researchers were surprised to find that adult brains responded as robustly as the younger animals’ brains, which typically are more adaptable.
“Our designed self-assembling peptide nanofiber scaffold created a good environment not only for axons to regenerate through the site of an acute injury but also to knit the brain tissue together,” said Zhang. The technique may be useful for helping close cuts in the brain made during surgery to remove tumors.
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