Green synthesis of silver nanoparticles using polysaccharides extracted from marine macro algae

•Green synthesis of silver nanoparticles using polysaccharides extracted from marine macroalgae.•The diameter range of the formed Ag-NPs depends on the algal species used.•The resultant Ag-NPs were applied to cotton fabrics with/without citric acid or a binder.•The treated fabrics showed excellent antibacterial activity.•The activity depends on type of the fabric treatment, size of the Ag-NPs and the algal species used. Green synthesis of nanoparticles that have environmentally acceptable solvent systems and eco-friendly reducing agents is of great importance. The aim of this work was to synthesis of silver nanoparticles (AgNPs) using water soluble polysaccharides extracted from four marine macro-algae, namely, Pterocladia capillacae (Pc), Jania rubins (Jr), Ulva faciata (Uf), and Colpmenia sinusa (Cs) as reducing agents for silver ions as well as stabilizing agents for the synthesized AgNPs. The formed Ag-NPs have been confirmed by UV–Vis spectroscopy, FTIR analysis and TEM. The resultant Ag-NPs colloidal solutions were applied to cotton fabrics in presence and absence of citric acid (CA) or a binder (B). The antimicrobial activity of the treated fabrics was evaluated. The results revealed that the antimicrobial activity depends on type of the fabric treatment, size of the synthesized Ag-NPs and the algal species used for polysaccharides extraction.