A 24-hour drug cocktail regrew much of a frog's leg

Bioengineers at Tufts University built a small wearable device, a silk-protein bioreactor sealed over the stump, that delivered five regenerative drugs to the wound for just 24 hours before being removed.

Adult African clawed frogs treated this way regrew a limb over the following 18 months that included new skin, bone, vasculature, and nerve tissue, and the animals used it to swim and respond to touch, outperforming untreated frogs that formed only a spike.

The drugs worked by briefly reactivating developmental signaling pathways, including Wnt and Notch, that are normally silent in an adult limb. The treated limb was not a perfect replica of the original, and whether the same 24-hour approach works in mammals is still being tested.

One day of treatment, 18 months of regrowth.