Facile fabrication of nonswellable and biocompatible hydrogels with cartilage-comparable performances

The preparation of high-performance hydrogels from biocompatible materials via a facile process has been increasingly studied but remains challenging. Herein, a nonswellable and biocompatible hydrogel was fabricated from polyvinyl alcohol and chitosan by multiple physical interactions without harmful crosslinkers. Owing to the synergy of salting-out effect and tridentate coordination, the network uniformity and stability were improved greatly. Compared with the precursor PVA-CS hydrogel, the crosslinking density increases from 76.9 to 157.8 mmol/cm3 accompanied by an increase in the gel fraction from 58.6 to 91.5%. In contrast, the average molecular weight between adjacent knots and mesh size decrease from 1650 to 1096 g/mol and from 6.1 to 4.8 nm, respectively. Benefited from the higher cross-linking density and more homogeneous gel framework, the obtained hydrogel exhibits cartilage-equivalent mechanical properties (tensile strength = 4.5 MPa, tensile strain = 299 %, elastic modulus = 1.2 MPa, toughness = 6.5 MJ m−3 and compressive stress = 8.4 MPa), combined with a high water content of 84.3 %. Remarkably, this hydrogel demonstrates excellent anti-swelling property due to the combination of high cross-linking density, water-resistant knots and dialysis process. The hydrogel barely expands after immersion in a PBS aqueous solution at 37 °C for 28 days. Moreover, both the tensile and compressive stresses remain exactly the same as their initial values, which is superior to most reported swelling-resistant hydrogels. Furthermore, the hydrogel shows good creep resistance upon external loading and cytocompatibility with HeLa cells, making it an ideal material for biotechnological applications. The full-fledged starting materials and facile methods of this hydrogel show its high potential for scale up and use in industrial applications.