Lignin-Mediated In Situ Silver Nanoparticle Bioactive Conductive Hydrogels for Regenerative Wound Healing, Energy Harvesting, and Motion Sensing Applications

Abstract

In this study, lignin−silver nanoparticle−polyacrylamide (lignin−AgNP−PAM) hybrid hydrogels were developed through persulfate-initiated free-radical polymerization for wound dressing, energy harvesting, and motion-sensing applications. Kraft lignin and milled wood lignin were incorporated at two different loadings to evaluate the formulation-dependent physicochemical, biological, and electromechanical performance. Lignin acted as a bioactive component and was proposed to assist the in situ formation and stabilization of AgNPs through its redox-active phenolic groups. FTIR analysis supported lignin incorporation and molecular interactions within the PAM network, while XRD indicated reduced semi-crystallinity following lignin addition and possible metallic silver formation in selected samples. Dynamic light scattering revealed lignin−silver hybrid particles with Z-average sizes ranging from 74 nm to 298 nm and polydispersity indices of 0.28−0.39. The hydrogels exhibited strong antioxidant activity, reaching approximately 88% ABTS radical-scavenging efficiency, and produced more than 87% antibacterial inhibition against Escherichia coli and Staphylococcus aureus under the tested conditions. Human dermal fibroblast viability remained above 85%, while M3 showed the highest viability and the lowest hemolysis, approximately 100% and 10%, respectively. Scratch assays demonstrated enhanced fibroblast migration, with K3 and M2 achieving approximately 90% and 92% wound closure, respectively, after 48 h. Proof-of-concept electromechanical testing of K2 generated triboelectric output up to approximately 28 V and distinct deformation-responsive signals near 1 V during finger motion. Overall, the hydrogels showed formulation-dependent trade-offs between bioactivity, blood compatibility, and electrical performance, supporting further optimization for wound contact and wearable sensing applications.