Electronic implants meld body, brain and machine

By Sarah Witman

Electronic implants to treat hearing loss, blindness and immobility are no longer limited to science fiction, scientists say.

Researchers from the U.S. and Europe spoke February 17 at the American Association for the Advancement of Science meeting in Boston to present new developments in this field of bionic medicine.

Konstantina Stanković, a professor at Harvard Medical School, described her lab's development of a safer and more accurate way to diagnose a condition called sensorineural hearing loss, or SNHL. Her team might now be able to power electronic devices using a natural energy source from within the ear, rather than batteries, she said.

Inner-ear nerve fibers and cells

Scientists used two-photon microscopy to image inner-ear nerve fibers (green) and cells (red) of the cochlear bone of a mouse ear. The technique could expose new aspects of deafness and hearing loss. Credit: Konstantina M. Stanković/Harvard Medical School

Sensorineural hearing loss “is the most common sensory neural deficit in the world and the most common congenital anomaly,” Stanković said. “It’s quite mind-boggling that we cannot biopsy the inner ear to establish diagnosis, and we cannot image cells in the inner ear to figure out why people are going deaf. This is what we are trying to change."

The main challenge of using an MRI or CT scan to guide SNHL operations is that the inner ear contains a delicate bone — the smallest in the human body — encased in the cranium, the thickest bone. Also, the inner ear is so close to the brain and carotid artery that it makes any operation highly delicate.

With Stanković's technique, scientists can inject inner-ear cells with fluorescent dye and excite the region with a laser to produce high-resolution images. This method, called endogenous two-photon excitation fluorescence, detects small changes within the ear caused by noise. It gives scientists a clearer picture of this inner-ear structure than ever before without further damaging hearing.

Scientists intend to “treat deafness with better vision," said Stanković, explaining that such imaging could make SNHL diagnostic tests more routine.

As for treating the disorder, her lab is working on technology that could eradicate bulky external wires and battery packs on monitoring devices implanted around the ear. The devices use the design of the inner ear, which contains a liquid called endocochlear potential (EP). The liquid acts as an electrochemical and works similar to a battery. Stanković successfully extracted energy stored within the EP of a guinea pig’s ear and used it to power a tiny electronic chip.

This energy-harvesting chip works in tandem with a wireless radio transmitter, collecting data from the EP and transmitting it to the researchers’ computers. Stanković said confirmation of EP as an effective biofuel suggests that scientists could use it in devices for monitoring and treating SNHL and possibly other forms of deafness in humans.

Stanković spoke as part of the AAAS session on “Engineering the Nervous System,” which featured four other researchers. Each has a similar goal of helping people cope with debilitating physical disabilities.

Silvestro Micera from the Swiss Federal Institute of Technology (EPFL) spoke about controlling prosthetic limbs solely with signals sent from an amputee’s brain. Grégoire Courtine, also from EPFL and working with the Christopher and Dana Reeve Foundation, talked about paraplegia therapy and his success in getting a lab rat to regain mobility, balanced with help from a robot. Harvard’s Joan Miller discussed approaches for restoring vision, and Philippe Renaud from EPFL presented bendable electronics that scientists could use to treat neurological disorders.

Courtine said he hopes the work will help “shift the paradigm” toward a future where bionic machines are sophisticated and accessible to a wide population.

Sarah Witman is a recent graduate of the University of Wisconsin, with a degree in journalism and a certificate in environmental studies. She currently interns with NASA's Air Quality Applied Sciences Team in Madison, doing web design and outreach. Reach Sarah at witmansarah@gmail.com or on Twitter @moshthebeadle.