Scientists say they've developed an implantable drug-delivery widget that harmlessly dissolves over time in the body, can be wirelessly charged, and has proven its efficacy in lab rats.

The academics, at Lanzhou and Dalian Universities in China and Penn State in the US, said their gadget is powered by a supercapacitor with a molybdenum sulfide (MoS₂) cathode, a zinc foil anode, and an alginate gel for an electrolyte. We're told this component can output 1.3 volts - enough to power a drug-delivery device for around ten days - before breaking down and being absorbed harmlessly by the host's body.

The idea here is that you implant this gizmo in a patient, and it releases medication into them over time, powered by this supercapacitor that can be easily wireless charged. Then at the end of treatment, the package dissolves completely and harmlessly, including its crude electronic circuit.

A paper describing the design explains how this approach could overcome a few problems in existing bioelectronics. While there are biodegradable batteries out there, they tend not to last long enough and discharge power in an unstable way, we're told. That means temporary implants either need to be tethered to a power source, or put up with piss-poor batteries, which isn't ideal; and those that are permanently implanted tend to be larger, rigid, and don't flex with the body.

Thus a small, bendy, wirelessly chargeable, and reliable source is preferred, and this molybdenum sulfide gizmo might be the ticket.

The boffins designed the power-storing implant to charge inductively using a magnesium coil, and to flex and move with the body. The device's various components - a charging coil, supercapacitor, control board, and a drug-delivery module - are all built on a poly-L-lactic acid substrate that's flexible and biodegradable.

Supercapacitors work like your typical capacitor, which stores energy in the electrical field between its plates, and are a battery alternative. Though these supercaps can't hold as much charge as a battery, they're small and good enough, and sufficiently stable and cool, to go into the body, we're told.

Fixing lab rat fevers

The researchers tested their design on laboratory rats suffering from a yeast-induced fever. Implants in the rats were configured to release the non-steroidal anti-inflammatory drug ibuprofen, with one group getting a charged implant, the other getting an implant without the supercapacitor being charged, and a third as a control group.

The implants functioned for the planned period of roughly ten days, the team said, after which they had degraded and could not hold a charge so were left to dissolve in the rats. Two months after being implanted there was "complete dissolution of the device," the team found.

The academics judged the experiment "an important step forward in advancing a wide range of transient implantable bioelectronic devices," while also admitting to unresolved issues such as an inability to turn the implant on or off without its power draining out.

"Achieving instant on and off of drug release is a very challenging problem that needs to be explored in depth," the boffins noted. Another insight was that the lifespan of the device could be varied by changing the thickness, microstructure, and chemistry of the wax and polymer coating in which the device is encapsulated.

This paper is not the first into biodegradable supercapacitors. The lead researcher on the drug-dispensing study, Hongwei Sheng, previously demonstrated the efficacy of molybdenum oxide supercapacitors implanted in rats in 2021, tho that research did not employ rechargeable devices. ®

https://www.theregister.com//2023/11/21/implantable_rechargable_supercapacitor_drugs/