Bacterial Cellulose Membranes Functionalized with In Situ Green- Synthesized Silver Nanoparticles for Antibacterial Applications

Bacterial cellulose (BC) is an attractive biopolymeric scaffold for the development of functional membranes due to its high purity, nanofibrillar network, mechanical robustness, and biocompatibility. In this work, we report the production and characterization of BC membranes functionalized with silver nanoparticles (AgNPs) generated through a plant-mediated green synthesis strategy, with particular emphasis on maximizing nanoparticle incorporation within the BC matrix. Mint (Mentha spicata) and avocado (Persea americana) extracts were employed as dual reducing and stabilizing agents for AgNP formation, enabling nanoparticle synthesis under mild and environmentally benign conditions. AgNP formation was first investigated in aqueous media as a function of silver precursor concentration, pH, and temperature, and monitored by UV–Vis spectroscopy through localized surface plasmon resonance (LSPR) features. Neutral pH (pH 7) and moderate temperature (23 °C) were identified as optimal conditions, yielding well-defined LSPR indicative of efficient and controlled nanoparticle formation. Two strategies for BC functionalization were subsequently compared: post-synthesis immersion of BC membranes in AgNP suspensions and in situ synthesis of AgNPs directly within the BC network. Spectroscopic analysis demonstrated that in situ synthesis enables significantly higher effective nanoparticle loading and a more homogeneous distribution throughout the BC scaffold, compared with the immersion approach.The resulting BC–AgNP composite membranes were subsequently evaluated for their antibacterial efficacy against Escherichia coli. Antibacterial performance was assessed using two complementary experimental stups. In the first, composite membranes were placed on agar surfaces uniformly seeded with E. coli, and the diameter of the resulting inhibition zones was measured following a defined incubation period as an indicator of bacteriostatic and bactericidal activity. In the second model, the BC–AgNP membranes were directly introduced into liquid cultures of E. coli, and bacterial growth was quantified by measuring the optical density (OD) of the cultures after incubation. This dual assay approach allowed for evaluation of both surface- mediated inhibition and the effects of AgNP release on planktonic bacterial growth. Membranes functionalized via in situ synthesis exhibited markedly enhanced antibacterial activity, with larger growth-inhibition zones and the absence of bacterial regrowth in both solid and liquid assays, confirming a predominantly bactericidal effect. Overall, this study demonstrates that combining bacterial cellulose with in situ green synthesis of silver nanoparticles is an effective strategy to maximize nanoparticle incorporation and produce robust antimicrobial membranes, offering strong potential for applications in wound dressings, filtration systems, antimicrobial packaging, and other sustainable functional materials.