Ultrathin silk-based electrons as brain implants

(Credit: John Rogers/Nature Materials)

Silk is not only flexible, it is also transparent and strong, and the rate at which it dissolves can be manipulated. So researchers at the University of Illinois, Urbana; Tufts in Boston; and the University of Pennsylvania decided to build silk-based brain implants, using electrode arrays with silk proteins and thin metal electrodes.
Since silk is biocompatible and water-soluble, it dissolved in the brains of the cats they studied, leaving the mesh-like electrodes, which are about 1/40 the thickness of a standard sheet of paper, literally hugging the brains' contours.
The cats were anesthetized, but their eyes still functioned, and the electrodes recorded the signals from their eyes as the cats were shown a series of images.
The result? These electrodes recorded signals from the cats' brains more accurately than the more traditional, stiff devices, which are about 30 times thicker.
"These implants have the potential to maximize the contact between electrodes and brain tissue, while minimizing damage to the brain," says Dr. Walter Koroshetz of the National Institute of Neurological Disorders and Stroke, a division of the Nation Institutes of Health, which contributed funding to the study.
These devices have the potential to help people with epilepsy, spinal cord injuries, and artificial limbs, report the researchers in the journal Nature Materials, which published the results on April 18.
The hope is that such a sensitive electrode will detect a seizure as it starts and deliver pulses to counteract it. For people with spinal cord injuries or prosthetics, brain signals might actually be routed directly to specific parts of the body. The researchers are also looking into building fully dissolvable implantable electronics to monitor and stimulate tissue growth. They say such technology could be extended for use in retinal and cochlear implants and even in treating a wide range of neurological disorders.