Silver ion competition reaction-triggered elastoplastic transition of chitosan hydrogel tubes

While the elastoplastic transition would significantly improve the tissue adaptability of hydrogel medical devices, achieving this mechanical transformation in situ under physiological conditions remains exceptionally challenging. Herein, this study proposes a silver ion-based competitive coordination reaction to achieve the elastoplastic transition of chitosan (Cs) hydrogel tubes within the human urinary tissue environment. The Cs hydrogel tubes (designated as B-T) are fabricated via the asymmetric crosslinking of Cs film strips induced by sodium tetraborate decahydrate (STD) in an aqueous solution. When B-T is immersed in a silver ion solution, the strong coordination interaction between silver ions and Cs converts it into a plastic Ag/B-T hydrogel tube. However, when Ag/B-T is exposed to human urine, the stronger chemical bonding interaction between silver ions and chloride ions in urine weakens the aforementioned coordination interaction between silver ions and Cs. This process further triggers the in-situ mechanical transition of the hydrogel tubes, which shifts the tubes from plastic Ag/B-T to elastic Na/B-T. The silver ions also endow hydrogel tubes with exceptional antibacterial efficacy and long-term anti-calcification properties. The combination of adaptive mechanical properties, antimicrobial performance, and calcification resistance establishes this hydrogel tube as a promising platform for the development of next-generation biocompatible urological implants.