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Green synthesis of silver nanoparticles using seaweed Fucus virosides and Cystoseira barbata extracts

The synthesis of silver nanoparticles (AgNPs) is an important area of research in nanotechnology due to their unusual size- and shape-dependent properties, strong antimicrobial activity and their attractive applications in medicine catalysis optoelectronics, and biotechnology. Various methods can be used for the synthesis of AgNPs such as the sol-gel method, chemical vapour deposition, or thermal decomposition, but these methods are often expensive and employ toxic chemicals. To overcome these drawbacks, biosynthetic approaches using water extracts from different organisms, including fungi, plants and algae, have recently emerged as simple and viable substitutes because they are simple, cheap, and environmentally friendly. Marine macroalgae or seaweeds, such as Fucus virsoides and Cystoseira barbata, are an abundant source of secondary metabolites such as polyphenols, polysaccharides, carotenoids, vitamins, minerals, amino acids, and proteins. Their aqueous extract can act as an efficient metal reducing agent as well as a capping agent to provide excellent stability to the formed nanoparticles. UV-visible spectroscopy is a very useful and reliable technique for the primary characterization of synthesized nanoparticles because the conducting electrons in the outer orbital of AgNPs resonate with specific wavelengths. Reduction of silver nitrate to AgNPs is confirmed with a peak in the range from 335 nm to 560 nm, while the absence of peaks indicates the absence of NP aggregation. In the present study, the water extracts of F. virsoides and C. barbata were used to prepare AgNPs by reducing Ag+ ions from a 1 mM silver nitrate solution to Ag0. Nanoparticle formation was confirmed by UV/Vis spectroscopy, with peaks detected at 380 nm for both algae. The antimicrobial activity of the synthesised nanoparticles against Bacillus subtilis, Pseudomonas aeruginosa Staphylococcus aureus, Salmonella thyphimunum, Enterococcus faecalis, Escherichia coli and Listera monocytogenes was investigated and compared with the antioxidant activity of the seaweed extracts.

antimicrobial activity, green synthesis, seaweed extracts, silver nanoparticles

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