Highly tunable coconut shell lignin-gelatin crosslinked hydrogel for controlled drug delivery in wound healing

Biopolymer-based hydrogels have emerged as promising materials for localized drug delivery and wound healing due to their biocompatibility and tunable properties. In this study, a biocompatible infrared (IR) dried hydrogel was developed using lignin extracted from coconut shell waste and gelatin, crosslinked via 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC), and evaluated for wound healing and localized drug delivery applications. Hydrogel samples with varying lignin content were prepared. The hydrogel containing 4 % lignin (LG4) has an optimal swelling capacity and mechanical stability. Dynamic Mechanical Analysis (DMA) further confirmed the viscoelastic stability of the optimized hydrogel. Amoxicillin loaded hydrogel achieved a drug loading efficiency of 77 ± 1.2 %. Cumulative in vitro drug release reached 78.0 ± 1.7 % at pH 7.4 over 72 h, following diffusion-controlled kinetics consistent with Korsmeyer-Peppas and Higuchi models. The hydrogel also demonstrated excellent cytocompatibility, >85 % cell viability in 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Extended MTT assays up to 10 days, along with confocal live/dead imaging, demonstrated sustained cell viability and adhesion. Biodegradation in Dulbecco's Modified Eagle Medium (DMEM) supplemented with lysozyme, along with SEM imaging of the dried hydrogel, provided complementary structural and degradation insights. These results highlight the potential of coconut shell extracted lignin-gelatin hydrogels as an eco-friendly platform for wound care.