Magnetoactive elastomer-based dynamic urethral support device for stress urinary incontinence

Abstract

Stress urinary incontinence (SUI) is the involuntary leakage of urine in response to increased intra-abdominal pressure during episodes of exertion. A common treatment method for SUI is sling implantation underneath the urethra to provide support. Most current sling procedures, however, cannot adjust urethral tension postoperatively. To address this limitation, we designed a soft magnetoactive elastomer (MAE) device capable of changing shape in response to moderate magnetic fields. To ensure shape change after fibrotic scar tissue encapsulation, MAE devices were embedded in agar gels with different stiffnesses, and their shape change was studied in response to up to 200 mT magnetic fields. A simple in vitro model of the lower urinary tract was designed to study device performance. Flow time was measured as a function of pressure in the simulated bladder as the model system leaked before and after activating sling with a hand-held magnet. MAE devices embedded in agar gel (100 kPa) in hammock-like configuration achieved 4.7% ± 1.1% change in height. Devices with silica-coated magnetic particles showed minimal loss in mass after two weeks in accelerated oxidative (2.36% ± 1.55%) and hydrolytic (0.58% ± 0.25%) conditions. Placing a sling under the model urethra provided urethral support; thus, increasing its resistance to flow. Normalized flow time significantly reduced from 1.56 ± 0.18 to 1.11 ± 0.16 when magnetic field was applied, indicating urethral support modulation at 60 cm-H₂O. This dynamic sling, powered externally with physiologically safe magnetic fields, allowed for urethral support modulation in a model of the lower urinary tract. STATEMENT OF SIGNIFICANCE: Stress urinary incontinence (SUI) affects up to half the adult women during their lifetime, and slings are commonly used to treat severe cases. While sling implantation is minimally invasive and offers moderate to high cure rates, long-term sling complications, such as urine retention, remain a significant concern. Available adjustable SUI devices often require invasive surgeries, implantable electronics, and multiple mechanical components, increasing the overall invasiveness. Here, we report a proof of concept for using shape-morphing biomaterials to fabricate a dynamic device that can provide continence support and be triggered to change shape, enabling complete voiding. Such a dynamic device may prevent many complications associated with traditional slings and improve quality of life for women suffering from severe SUI.

Keywords: Magnetoactive elastomers; Medical devices; Shapechanging polymers; Stress urinary incontinence.