While there are already a variety of implants that dispense medication within the body, most of them either can't be externally controlled, or they eventually have to be surgically removed. A new one, however, uses light to avoid both problems.
The majority of existing drug-dispensing implants take one of two forms.
One type harmlessly biodegrades over time – so it doesn't have to be removed – but it only delivers its medication at a preset rate. This means that if the patient needs their implant to release more of a painkilling drug at certain times, for instance, they have no way of making it do so.
The other type of implant can be remotely activated via radio signals or other means, but it contains electronic components that aren't biodegradable. This means that if the patient doesn't want the device to stay in their body indefinitely, where it could potentially cause problems down the road, it has to be removed in a second surgical procedure.
Developed by scientists at Chicago's Shirley Ryan AbilityLab and Northwestern University, the experimental new device combines the best features of both types of implant.
The current prototype is made of magnesium, molybdenum and a polyanhydride polymer – all of which are biodegradable – and consists of three drug-filled reservoirs, each of which is incorporated into a biodegradable battery. That battery's anode seals the reservoir, and is connected to its cathode via a phototransistor.
The phototransistor's electrical resistance drops when it's exposed to a certain wavelength of light, short-circuiting the battery. The reservoir-sealing anode corrodes as a result, allowing the medication to diffuse out into the surrounding tissue.
Because each reservoir's phototransistor is sensitive to a different wavelength of light, the implant is able to release drugs three separate times – each time using a different type of light. In lab tests performed so far, the implant was successfully used to release the painkilling drug lidocaine in rats. The light source consisted of three differently colored external LEDs, which shone through the animals' skin and underlying tissue at the implant site.
"This technology represents a breakthrough addressing shortfalls of current drug delivery systems – one that could have important and sweeping implications for everything from the opioid epidemic to how cancer treatments are precisely delivered," said Shirley Ryan AbilityLab's Dr. Colin Franz, who led the study along with Northwestern University's Dr. Yamin Zhang and Dr. John Rogers.
A paper on the research was recently published in the journal Proceedings of the National Academy of Sciences.
Source: Shirley Ryan AbilityLab
