Sustainable ZnO/Zn₃(PO₄)₂ Nanoparticles Synthesized from Coconut-Derived Media Incorporated into Bioactive ALG/PVA Hydrogel Dressings

The adaptive nature of bacteria and their increasing resistance to conventional therapies demand alternative strategies to effectively control wound infections. At the wound site, dynamic biological processes are easily disrupted by microbial colonization, compromising normal healing. In this study, Zn-based nanoparticles composed of zinc oxide (ZnO) and zinc phosphate (Zn₃(PO₄)₂) were synthesized via a green route using coconut milk and coconut water as biological media. Although ZnO formation via zinc hydroxide intermediates was initially targeted, structural analyses revealed a multiphase Zn-based system resulting from interactions between Zn²⁺ ions and naturally occurring phosphate species in the coconut-derived sources. The resulting material was incorporated into sodium alginate/poly(vinyl alcohol) hydrogel dressings, further enhanced with spirulina and aronia powders. Physicochemical characterization (XRD, SEM, EDS, FTIR), along with swelling and degradation studies, confirmed structural stability and appropriate hydrogel behavior. Antimicrobial testing against <i>Staphylococcus aureus</i> and <i>Escherichia coli</i> demonstrated a dominant antibiofilm effect of the Zn-based nanoparticles, while botanical additives exhibited moderate, time-dependent activity. Biological evaluation demonstrated good cytocompatibility toward human keratinocytes and murine macrophages, with botanical additives mitigating mild nanoparticle-induced cellular responses.