Hybrid kraft lignin-copper oxide nanoparticles as functional additives in natural rubber membranes for biomedical applications.

Lignin‑copper oxide hybrid nanoparticles (LNCuNPs) were synthesized via in situ reduction and incorporated into natural rubber latex (NR) membranes ate concentration from 1 to 4% wt% to develop bioactive biocomposites for wound dressing applications. Among the evaluated systems, LNCuNPs exhibited superior colloidal stability, lower polydispersity, and a narrower size distribution compared with the control CuONP systems. Structural analyses confirmed the successful physical incorporation of nanohybrids into the NR matrix, with no evidence of covalent interactions or significant alterations in thermal stability. The presence of LN-derived oxygen-containing groups increased surface polarity and modulated membrane wettability. Mechanically, LNCuNPs increased Young's modulus and reduced elongation at break, consistent with the typical reinforcement effect induced by particulate fillers and the reduced extensibility associated with particle-matrix interfacial constraints and/or the formation of rigid filler domains at higher loadings. The membranes demonstrated notable antimicrobial activity against Staphylococcus aureus. Biological evaluation using L929 fibroblasts demonstrated high cytocompatibility across all formulations. Scratch assays reveal enhanced cell migration and near-complete wound closure after 48 h for membranes containing 1% and 2 wt% LNCuNPs, whereas membranes containing 4 wt% LNCuNP exhibited reduced migratory performance. Overall, the controlled incorporation of LNCuNPs into NR resulted mechanically reinforced, cytocompatibility membranes with antimicrobial activity, and promising potential for sustainable wound dressings for tissue repair.