Qian N. et al., 2025: In Situ Cross-Linked Chitosan/Hyaluronic Acid Hydrogel for Removing Kidney Stone Fragments after Lithotripsy Surgery.

Qian N, He M, Wang K, He C, Chen Y
ACS Appl Bio Mater. 2025 Oct 20;8(10):9140-9144. doi: 10.1021/acsabm.5c01297.

Abstract

Kidney stones are small hard stones formed by the accumulation of minerals in the urine in the kidneys. Approximately 80% of kidney stones are calcium salt stones in which calcium ions are easily complexed with carboxyl groups through electrostatic interaction, coordination bond formation, chelation, and hydrogen bond assistance. In addition to open surgical stone removal, laser lithotripsy surgery (or extracorporeal shock wave lithotripsy) has also been widely used to effectively break up stones in the kidneys, but it is often difficult to remove them from the kidney completely. To address this problem, we developed a promising method to remove kidney stone fragments from the kidneys with a chitosan/hyaluronic acid-based magnetic hydrogel. The mixture of N-succinyl chitosan (NSC), oxidized hyaluronic acid (OHA), and ferric oxide (Fe3O4) nanoparticles will be rapidly cross-linked into a magnetic hydrogel within 1 min in the presence of calcium ions. With the increase in the Fe3O4 content (0 → 17.24 wt % → 29.41 wt % → 38.46 wt %), the viscosity of the as-prepared hydrogel also increased from 562.80 to 855.09, 1099.92, and 1127.84 Pa·s. By comparison with the control group (Roswell Park Memorial Institute (RPMI)-1640), for all the magnetic hydrogels, a cell viability of more than 85% was achieved, suggesting good cytocompatibility of NSC-OHA-based hydrogels. The NSC-OHA-Fe3O4 hydrogels encapsulating kidney stone fragments can be easily removed by a magnetic tool, which provides a potential solution for the removal of residual kidney stone fragments in the kidney after laser lithotripsy surgery.

Comment Peter Alken

Nice small study on the problem of residual fragments after whatever kind of disintegration. Animal experiments and clinical trials may follow.

They don’t mention some studies done in Germany (1,2). I am not sure what will finally survive: ultrasound propulsion (3) or adhesive gels.

1 Hein S, Schoenthaler M, Wilhelm K, Schlager D, Thiel K, Brandmann M, Richter K, Grunwald I, Wetterauer U, Miernik A. Novel Biocompatible Adhesive for Intrarenal Embedding and Endoscopic Removal of Small Residual Fragments after Minimally Invasive Stone Treatment in an Ex Vivo Porcine Kidney Model: Initial Evaluation of a Prototype. J Urol. 2016 Dec;196(6):1772-1777. doi: 10.1016/j.juro.2016.05.094. Epub 2016 May 30. PMID: 27256206.

2 Amiel T, Neisius A, Netsch C, Secker A, Fisang C, Grunwald I, Lunger L, Straub M. Stone extraction during flexible ureterorenoscopy with or without the hydrogel method: a randomized, multicenter safety and feasibility study. World J Urol. 2025 Oct 31;43(1):655. doi: 10.1007/s00345-025-06011-7. PMID: 41171315; PMCID: PMC12578769.

3 Sorensen MD, Dunmire B, Thiel J, Cunitz BW, Burke BH, Levchak BJ, Popchoi C, Holmes AE, Kucewicz JC, Hall MK, Dighe M, Dai JC, Cormack FC, Liu Z, Bailey MR, Porter MP, Harper JD. Randomized Controlled Trial of Ultrasonic Propulsion-Facilitated Clearance of Residual Kidney Stone Fragments vs Observation. J Urol. 2024 Dec;212(6):811-820. doi: 10.1097/JU.0000000000004186. Epub 2024 Aug 15. PMID: 39146526; PMCID: PMC11560600.

Peter Alken