MIT implant delivers drugs and the light that activates them
When taken orally or intravenously, medications typically travel throughout the body, producing unwanted side effects. MIT scientists are working on an alternative, that delivers both light and a light-activated drug directly to the target area.
So-called "photoswitchable" drugs contain light-sensitive molecules that essentially switch the drug on when exposed to a flash of light. This means that a pharmaceutical could remain inactive when moving through the bloodstream or digestive tract, only becoming active once it reached the place it was needed. As a result, few if any side effects would occur.
That said, how could a flash of light be delivered precisely to the target area, right when the drug was present at that location? Well, that's where a device developed by the MIT researchers comes into play.
It's made up of two very thin multi-material fibers, joined side-by-side like the barrels of a double-barrelled shotgun. One of them is actually a fluidic channel (a tiny tube), that delivers the medication. The other is an optical fiber that delivers a beam of light.
A technique known as thermal drawing was used to create the device. Putting it simply, this involved first creating a larger version of the two joined fibers, heating them to the melting point, and then stretching them lengthwise to make them both longer and much skinnier. The finished product is mere micrometers (millionths of a meter) in width, so it can be surgically inserted into living tissue with a minimum of damage.
In lab tests, the device was inserted into the ventral tegmental area – basically the reward center – in the brains of live mice. It was then used to deliver a virus that boosted the expression of a key receptor (TRPV1) on neurons in that region.
After several weeks, the device was utilized to deliver both visible green light and a photoswitchable version of capsaicin (a chemical compound found in red peppers) to those same neurons. The light activated the capsaicin analog, causing it to bind with the TRVP1 and thus trigger the neurons' reward response.
As a control, in separate chambers of the mouse enclosure, the device was used to deliver a virus that did not boost TRVP1 expression, and it was also used to deliver a wavelength of light that didn't activate the capsaicin analog. The mice subsequently showed a preference for going into the chamber where the proper virus and proper light had been administered, suggesting they associated that chamber with pleasurable feelings.
A paper on the research, which was led by MIT's Assoc. Prof. Polina Anikeeva and Oregon Health and Science University's Prof. James Frank, has been published in the journal ACS Chemical Neuroscience.