Magnetic hydrogel may facilitate efficient removal of kidney stones: Study

About one in nine individuals are affected by kidney stones, causing intense pain and severe infections. They pose a significant health burden, with over 1.3 million emergency room visits and healthcare expenditures exceeding $5 billion annually in the US. The most common treatment is laser fragmentation through ureteroscopy, but success rates in stone elimination range from 60% to 75%. Small, hard-to-extract fragments are often left behind, risking natural elimination. Technologies like fragment adhesion with biopolymers, focused ultrasound, and negative pressure aspiration have been explored, but they have limitations, especially with standard ureteroscope channel sizes.

The study introduced the Magnetic System for Total Nephrolith Extraction, a system designed to enhance the efficiency of renal calculus fragment removal. In this system, the stones are coated with a magnetic hydrogel and retrieved using a magnetic guidewire compatible with standard ureteroscopes.

In vitro, the separation of laser-obtained renal calculus fragments was done by size and coated either with ferumoxytol alone or combined with chitosan (Hydrogel CF). Then, the treated fragments were subjected to a magnetic wire for fragment removal assessment.

Additional tests included scanning electron microscopy and cell culture with human urothelial cells to assess the cytotoxicity of the magnetic hydrogel components. The hydrogel and its components underwent efficacy and safety evaluations in in-vitro studies, murine models, and human tissue samples to assess their impact on urothelium and antibacterial properties.

The Hydrogel CF comprising chitosan and ferumoxytol showed 100% effectiveness in eliminating all tested fragments, even those measuring up to 4 mm, across various stone compositions. Particle tracing simulations indicated that small-sized stones measuring 1 and 3 mm could be captured several millimetres away. The binding of ferumoxytol and Hydrogel CF to the surface of calcium oxalate stones was confirmed by scanning electron microscopy.

Even after a 4-hour exposure, Hydrogel CF components did not induce significant cytotoxicity on human urothelial cells. Moreover, live mouse studies revealed that Hydrogel CF caused less bladder urothelium exfoliation compared with chitosan, and the urothelium returned to normal within 12 hours. In addition, these components exhibited antibacterial properties, inhibiting the growth of uropathogenic bacteria such as Escherichia coli and Proteus mirabilis, comparable to that of ciprofloxacin.

The ability to eliminate lithiasic fragments, the absence of significant urothelial toxicity, and antibacterial activity indicate that magnetic hydrogel use could be integrated into laser treatments for renal stones through ureteroscopy without immediate complications.

"By enabling the efficient retrieval of kidney stone fragments, our method can lead to improved patient outcomes and stone-free rates," the research team wrote.

"The antibacterial properties could offer potential postoperative benefits while decreasing procedural time," they concluded. "Further animal studies are underway to assess Hydrogel CF's safety before proceeding to human clinical trials."