MIT researchers have developed a medical-device coating that releases precise doses of drugs under the control of electrical signals, according to Technology Review. The thin film, which consists of only the drug itself and an electrically active compound, might be coated onto stents, knee replacements, and even fully biodegradable patches of polymers for drug delivery, the mag writes. The researchers say that any therapeutic substance, from anticancer drugs to antibiotics, could be used in the coating.

The films, only a few hundred nanometers thick, are made up of layers of drugs and layers of a compound called Prussian blue, which is commonly used as a dye, but has also been used to develop displays because it changes its color and charge when an electric field is applied. The films, developed by Paula Hammond, a professor of chemical engineering at MIT, take advantage of this change in charge, from negative to neutral. The films are put down layer by layer: a layer of drug, followed by a layer of Prussian blue. With the application of an electric field…a layer of drug is released.

Hammond says that the timing and level of the dosages released from the film can be very closely controlled, depending on how much drug is loaded into each layer and how many layers are allowed to disintegrate before the electric field is turned off. So far, Hammond has demonstrated a four-layer version of the film with a model drug. She believes that the films could be made up of many more layers and might be laid down on devices in patches, each of which might contain a different type of drug. Prussian blue has more than one charge state, so it’s possible to make films that are activated by different strengths of electrical fields; such films could release different drugs at different times.

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