Wirelessly-activated implant treats bladder problems using light
Currently, if people have urinary problems such as incontinence or an overactive bladder, medication and/or electronic nerve-stimulating implants are required. An experimental new implant may work better, however, treating the problem using integrated micro-LEDs.
Presently-used implants regulate bladder function by delivering an electrical current to the nerve that controls the organ. Unfortunately, though, these devices sometimes disrupt normal nerve signalling to other organs, causing off-target side effects. Medication can likewise cause unwanted side effects of its own.
With these limitations in mind, scientists from the Washington University School of Medicine in St. Louis, the University of Illinois and Northwestern University developed the prototype soft-bodied implant. In lab rat experiments, the battery-free device was implanted via a "minor surgical procedure," being wrapped like a stretchy belt around the animals' bladders.
The researchers also injected proteins known as opsins into the organs. These proteins were carried by a virus that binds to the bladder's nerve cells, causing them to become sensitive to light signals.
As the rats' bladders subsequently filled with urine and then emptied, the implant detected the associated expansion and relaxation of the organ. This data was transmitted by Bluetooth to an external hand-held reader device – it utilized algorithms to determine when the bladder really was full and legitimately needed to be emptied, and when it was emptying too frequently. In the latter cases, the reader automatically prompted the implant to activate its LEDs, illuminating the nerve cells. This reduced the activity of those cells, restoring normal bladder function.
The researchers now plan on making larger implants for use in other animal trials, with an eye towards eventually developing a model for use in humans. It is thought that implants incorporating the same technology could also be used in other parts of the body, for applications such as the management of chronic pain, or for stimulating the pancreas to secrete insulin as needed.
Before that can happen, however, more research is required.
"We don't yet know whether we can achieve stable expression of the opsins using the viral approach and, more importantly, whether this will be safe over the long term," says Washington University's Prof. Robert W. Gereau, one of the senior authors of a paper on the study. "That issue needs to be tested in preclinical models and early clinical trials to make sure the strategy is completely safe."
The paper was recently published in the journal Nature.