Matchstick-sized, transparent polymer implants containing synthetic cells that are genetically modified to activate in response to light can provide specific and local in-body therapies to mice, according to a report published online in Nature Photonics. Such implants could be important for a wide range of diagnostic and therapeutic applications, such as an optical treatment for diabetes or real-time monitoring of toxins in the body.

As a first demonstration of the medical utility of such light-activated implants, Seok Yun and colleagues regulate blood glucose levels in diabetic mice. They used blue light supplied through an optical fibre to the implant, to induce the cells in the implant to synthesize a protein that stimulates insulin production. In another demonstration, the team created implants with cells that emit green light when stressed by the presence of certain toxins such as heavy metals. By measuring light levels emitted by the implant, such implants in the future could be used as sensors for monitoring toxin levels in patients in real time. The approach works because the implants are both highly transparent and biocompatible.