By implanting a transparent gel that contains genetically modified light-sensitive cells, researchers have demonstrated a new type of implant that could one day be used to treat disease and monitor toxins in people.
"Light is a great tool to interface with biological systems, but there is a fundamental problem. It gets scattered when it hits tissue, and at depths much thinner than our skin," says lead author Myunghwan Choi of Harvard Medical School in Boston.
Choi and his colleagues designed an implantable gel that could get around this, by guiding light under the mouse's skin. In experiments, the team impregnated the gel with different types of genetically modified cells before implanting it.
To control diabetes, the team shone light into the mouse and at the implanted gel using a fibre optic cable attached to its head. The light triggered cells in the gel to produce a compound that stimulated the secretion of insulin and stabilised blood glucose levels. Separately, the team also showed they could monitor for cadmium poisoning using cells that fluoresced when the mouse was under stress from the toxin.
Though still at the prototype stage, the ultimate idea is to reduce the need for doctors to perform repeated injections and blood tests to monitor or treat patients.
"The promise is there," agrees Fiorenzo Omenetto, a biotechnologist at Tufts University in Medford, Massachusetts. But he adds it will have to get a little easier to live with than the current implant. "The tough thing here is the presence of a large implant and a fibre sticking out of your head. Not something I'd want if I were diabetic."
Choi's team plans to work on making the gel more user-friendly. For example, he says, "we are thinking of adding a micro-LED with a wireless power receiver to the gel implant."
"Genetically modified cells have been engineered for a variety of applications ranging from the treatment of cancer to the prevention of gout," wrote Warren Chan of the University of Toronto, Canada, in a comment piece published alongside the work. "This suggests that the implantable hydrogel could be used for many biological and clinical applications."