Harvard Medical School researchers have developed a way to deliver a light signal to specific tissues deep within the body. Called a light-guiding hydrogel, the implant is constructed from a polymer-based scaffolding capable of supporting living cells. The hydrogel contains cells genetically engineered either to carry out a specific activity in response to light or to emit light in response to a particular metabolic signal. An optical fiber connects the implant to an external light source or light detector.
In one experiment, the scientists used programmed HeLa cells that were caused to emit a kind of protein when exposed to light. When that protein is produced in the body, the pancreas creates more insulin. A means of controlling diabetes was shown. In another experiment, the researchers filled the hydrogel with cells that light up when exposed to a certain toxin, then after implanting the hydrogel, injected mice with the toxin. Using the fiber cable in reverse, the researchers were able to see the cells in the hydrogel lighting up in response to the presence of the toxin