Patients with type 1 diabetes rely on daily insulin injections to help regulate their blood glucose. Now, researchers have devised a potentially less invasive way to deliver the drug: an insulin-carrying gel that can be placed under the skin and activated by light to release the hormone when needed (Mol. Pharmaceutics 2016, DOI: 10.1021/acs.molpharmaceut.6b00633). To make the material, Simon H. Friedman of the University of Missouri, Kansas City, and colleagues linked human insulin molecules to a commercially available gel—a copolymer made of polystyrene and polyethylene glycol—using a linker molecule containing a light-sensitive chemical bond. When exposed to 365-nm-wavelength light, this bond breaks, releasing the insulin. To test the material, the researchers injected 10-μm-diameter beads of the gel under the skin of diabetic rats and attached a coin-sized light-emitting device over the area. The researchers switched on the light for two minutes, then monitored the animals’ blood glucose and insulin levels. Insulin release began a few minutes after light exposure, peaked at 25 minutes, and then plateaued. The researchers found that blood glucose levels dropped in response to insulin and that they could reactivate the gel 65 minutes later to release a second dose of the hormone.