Bioelectronics herald the rise of the cyborg.

SCIENCE sciencemag.org P H O T O S : L IE B E R G R O U P , H A R V A R D U N IV E R S IT Y T he wires emerging from the heads of the small black mice—strain C57BL6—are a tip-off. If you’re a scifi aficionado, you know that this is how cyborgs get their start. Charles Lieber, a chemist at Harvard University, and his colleagues have injected the brains of the mice with tiny, meshlike electronic probes—flexible and invisible to the immune system—that can eavesdrop on neurons for months at a time. Standard electrodes can’t match that longevity, nor can they match another feat that Lieber reported at a meeting of the Materials Research Society here in Boston last week: simultaneously recording neural chatter in the eye alongside two other visual processing centers in the brain. Lieber’s result, together with other advances on display at the meeting, heralds a new era in bioelectronics, when electronics integrated seamlessly into nervous tissue could lead to innovative treatments in humans for everything from blindness and paralysis to brain diseases such as Parkinson’s and Alzheimer’s. For now, the researchers are working mostly in animals, and are primarily just listening to neural activity to understand the brain. But because the electrodes can carry inputs as well as outputs, the day when Lieber will not just monitor his mice, but also control them, is not far off. The boundary between living organisms and the outside world is dissolving, says David Martin, a bioelectronics expert at the University of Delaware in Newark. “You have to ask: Where does life end and engineering begin?” For decades, neuroscientists have inserted thin, metallic probes into the brains of mice and other animals to investigate the basic operation of neural circuitry, and those electrodes are growing ever more capable. Last month, for example, an international team of researchers reported the creation of ultrathin metallic probes capable of simultaneously tracking neural activity from hundreds of different spots along each probe. Clinicians already use related metallic probes in a therapy called deep brain stimulation, in which neurons are triggered to tamp down the muscular tremors associated with Parkinson’s and other diseases. But even thin metal spears can damage nerve tissue when inserted in the brain, Lieber says. And in the subsequent weeks to months, immune cells typically attack these rigid foreign objects, creating an inflammatory response and scar tissue that isolates the probes and renders them less effective over time. So Lieber and others are crafting biofriendly alternatives. His group, for example, devised meshlike electrodes made from ultrathin gold wires wrapped in biofriendly organic polymers—plastics that have the suppleness of cells. The resulting electrodes are flexible enough to be suspended in a watery fluid, sucked into a syringe, and injected I N D E P T H