In Situ Cross-Linked Chitosan/Hyaluronic Acid Hydrogel for Removing Kidney Stone Fragments after Lithotripsy Surgery

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 <i>N</i>-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.