Eumelanin-loaded ZnO@Ag/kombucha-derived bacterial cellulose gauze as a multifunctional bioactive dressing for antimicrobial and pro-healing applications.

Abstract

Developing sustainable wound dressings that combine antimicrobial activity, antioxidant activity, cytocompatibility, and adequate mechanical performance remains challenging. To address this, an eco-friendly multifunctional dressing was fabricated by integrating a kombucha-derived bacterial cellulose/ZnO@Ag (KBC/ZnO@Ag) nanohybrid and eumelanin derived from Hermetia illucens puparia within a hydroxypropyl methylcellulose (HPMC) matrix. The structural, chemical, morphological, thermal, optical, and elemental properties of the prepared materials were evaluated using XRD, FTIR, SEM-EDX, TGA/DTG, photoluminescence, and atomic absorption spectroscopy. Among the tested formulations, the eumelanin-containing KBC/ZnO@Ag formulation (S4-EuMe) exhibited broad-spectrum antimicrobial activity against Gram-positive and Gram-negative bacteria and Candida albicans, with inhibition zones of up to 47 mm. Eumelanin incorporation further enhanced antioxidant activity, reducing the DPPH radical-scavenging IC₅₀ from 26 μg mL^-1 for KBC/ZnO@Ag (S4) to 14 μg mL^-1 for S4-EuMe. The selected formulation also showed a concentration-dependent effect on HFB4 fibroblast viability, with an IC₅₀ of 177.45 ± 1.35 μg mL^-1, and enhanced in vitro scratch closure to 72.72% after 48 h compared with 60.73% for the untreated control. Mechanically, S4-treated gauze showed reduced tensile strength and stiffness relative to the neat substrate, whereas eumelanin incorporation in S4-EuMe increased tensile strength, stiffness, and Young's modulus. In the corresponding freeze-dried scaffold, eumelanin also enhanced resistance to repeated compression, increasing the mean compressive stress over 15 loading-unloading cycles from 8.15 ± 0.52 to 13.16 ± 1.23 kPa. Overall, S4-EuMe integrates complementary antimicrobial and antioxidant activities, cytocompatibility, fibroblast-associated effects, and favorable mechanical properties, supporting its potential as a sustainable bioactive wound-dressing material for further investigation.