Ultrasound-Activated Microstructures Clean Implanted Stents and Catheters

Urinary stents and catheters are medical devices commonly used in both human and veterinary medicine to facilitate the drainage of urine to or from the bladder. Ureteral stents are specifically employed when the ureter—the tube connecting the kidney to the bladder—becomes obstructed due to conditions such as tumors, pregnancy, kidney stones, or anatomical narrowing. After implantation, bacterial biofilms and crystalline deposits, known as encrustations, begin to form on the surfaces of these devices. These biofilms and encrustations are major contributors to the failure of urinary stents and catheters, leading to blockages, infections, and considerable pain. To prevent such issues, stents and catheters generally need to be replaced every two to six months. This frequent replacement not only impacts the quality of life for patients but also contributes to high healthcare costs and places a strain on hospital resources. Now, researchers have developed a non-invasive cleaning method that could reduce the frequency of stent replacements, minimize infection risks, and ease the burden on patients and healthcare systems.

In a new study, an interdisciplinary team, including researchers from ETH Zurich (Zurich, Switzerland), recreated the conditions and structure of stented ureters and demonstrated that ultrasound-activated artificial cilia on the stent surfaces can effectively remove both biofilms and encrustations. The researchers envision incorporating cilia on both the inner and outer walls of future medical devices. These cilia, activated by ultrasound through the skin, would create an efficient streaming motion that loosens bacteria and crystal formations from the stent surfaces, allowing them to be flushed away. This non-invasive cleaning process significantly reduces the risks of obstruction. The findings, published in PNAS, showed that ultrasound waves alone produce minimal streaming when they strike smooth surfaces. However, when the surface contains micro-structures like cilia, a highly efficient form of streaming—known as acoustic streaming—was created.

The results from the microfluidics experiments far exceeded the researchers’ expectations. In every test, typical biofilms and encrustations found in urinary stents and catheters were removed within seconds or minutes using this technology. The potential applications for this technology extend beyond urology, with potential uses in areas such as visceral surgery and veterinary medicine, where cleaning implanted devices is also crucial. Non-invasive ultrasonic cleaning could reduce the need for repeated invasive procedures, significantly improving patient quality of life and lowering the number of outpatient visits. The promising results of this feasibility study set the stage for the next step—developing a prototype that will be tested in animal models.

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