Overactive bladder syndrome (OBS) causes a frequent, uncontrolled urge to urinate, which can interfere with a person’s daily activities and affect their mental health. A new hydrogel-based device has been developed that can continuously monitor overactive bladders and has the potential to improve the treatment of the condition.
The detrusor muscle lines the bladder wall. Controlled by nerves, in healthy people, the muscle relaxes to keep urine in and contracts when a person urinates. But in people with OBS, the muscle is overactive, resulting in a sudden urge to urinate, frequent urination (more than eight times a day, more than twice overnight) and, occasionally, incontinence.
OBS affects 12.8% of women and 10.8% of men worldwide. The uncontrolled nature of the condition means that, in addition to experiencing symptoms, people often suffer from adverse effects such as decreased work productivity, diminished sexual satisfaction, poor mental health and higher rates of anxiety and depression, and decreased sleep quality. Moreover, if left untreated, OBS can lead to kidney dysfunction and failure.
Although the condition can be treated with medication, for some, medication is ineffective. A relatively new treatment applies electrical stimulation to the nerves connected to the bladder to reduce overactivity. However, without monitoring bladder activity, it can be hard to determine what the right amount of stimulation is. The stimulation must be just right; otherwise, the treatment is ineffective.
Full electromechanical measurement of bladder and detrusor muscle activity is needed to monitor OBS accurately. Past iterations of bladder monitoring devices have focused on mechanical contraction and relaxation, but the body movements associated with everyday activity can interfere with signal quality. Further, they did not include electromyography (EMG) to monitor the bladder’s bioelectrical or nerve activities.
With these limitations in mind, researchers from the Pohang University of Science and Technology (POSTECH) in South Korea designed a multifunctional implantable sensor that measures bladder volume, mechanical contraction and relaxation, and nerve activities all in one platform.
Because the USH-SI sensor, an acronym for ultra-soft hydrogel combined with structurally engineered islets, is made of highly elastic hydrogel, it adhered more easily and firmly to bladder tissue compared with traditional silicone sensors.
In experiments conducted on a pig and a rat, the researchers found that the sensor could continuously monitor electromechanical activity in real time. And the device is small enough to be inserted using laparoscopic (“keyhole”) surgery.
“The new sensor shows that sensors can be made small enough to be inserted by surgical-robot-assisted laparoscopic surgery," said Professor Steve Park, corresponding author of the study. "This has the potential to minimize the time taken for a patient to recover and reduce side effects.”
The researchers are developing high-resolution and multiarray sensors that would enable spatial-temporal analysis of bladder activity. They are also working on a fully implantable feedback system that incorporates a nerve stimulator, allowing for both diagnosis and treatment of OBS and, potentially, other conditions.
“We combined the USH-SI sensor with a neural stimulator targeted to treat overactive bladders, a chronic condition,” said Professor Sung-Min Park, lead author of the study. “This allows for monitoring and neural stimulation simultaneously. We expect it to be a platform that can be applied to other internal organs.”
The study was published in the journal Biosensors and Bioelectronics.
