An injectable, self-healing, and robust double-network composite hydrogel with incorporation of nano-lignin

Injectable and self-healing hydrogels with tunable physicochemical properties hold great potential in many biomedical fields, including wound dressings, drug delivery, and tissue engineering. However, the dynamic properties of these hydrogels are often inversely related to their mechanical strength , and their preparation processes are typically complex. To solve these problems, we developed a nanocomposite hydrogel using a simple one-pot method combined with freeze-thaw cycles (F-T). This hydrogel consists of polyvinyl alcohol (PVA), boric acid (BA), sodium polyacrylate (PAANa), and lignin, formed through chemical reactions and multiple dynamic reversible interactions (borate esters and numerous hydrogen bonds). It exhibits excellent mechanical properties (tensile strength of up to 502 kPa and an elongation at break of about 632 %), self-healing capabilities, and injectability. Nano-lignin, rich in phenolic hydroxyl and methoxy groups, functions as a reinforcing agent and physical cross-linker in the hydrogel via non-covalent interactions of its surface functional groups with PVA's hydroxyl groups. Incorporation of nano-lignin boosts its performance (mechanical, self-healing, and injectability) by creating multiple crosslinking points within hydrogel. Moreover, nano-lignin addition enhances the hydrogel's water retention and swelling properties. This study presents a promising strategy for fabricating injectable self-healing hydrogels with exceptional mechanical properties, offering vast potential in biomedical fields. • Hydrogel was fabricated via a simple one-pot method combined with freeze-thaw cycles. • Multiple-crosslinked hydrogel exhibited excellent self-healing and injectability attributes. • Lignin enhanced functionality by forming multiple-crosslinking points within hydrogel. • The hydrogel had great application prospects in drug injection.