Cobweb as novel biomaterial for the green and eco-friendly synthesis of silver nanoparticles

In this study, spider cobweb as a novel biomaterial was used for the green synthesis of silver nanoparticles (AgNPs). The synthesized AgNPs were characterized using UV–Vis spectroscopy, Fourier-transform infrared spectroscopy (FTIR), and transmission electron microscopy. The efficacy of biosynthesized particles as antibacterial agents was evaluated using multi-drug resistant clinical bacterial isolates through sensitivity testing with AgNPs and combination of AgNPs with some selected antibiotics. In addition, the potential application of the particles as additives in paints was demonstrated using some bacterial and fungal isolates. The synthesized AgNPs which were dark brown in color displayed maximum absorbance at the wavelength of 436 nm. It was observed that the reaction mixture of 1:40 (extract:AgNO3 solution) at pH of 8.5 produced particles with maximum absorbance at 436 nm. The FTIR spectrum showed peaks at 3298, 2359, 2089, and 1635 cm−1, indicating that proteins were the capping and stabilization molecules in the synthesis of AgNPs. The particles were spherical in shape with size ranging about 3–50 nm. The energy-dispersive X-ray analysis showed the presence of silver as the most prominent metal, while the selected area electron diffraction pattern conformed to the face-centered cubic phase and crystalline nature of AgNPs. The AgNPs inhibited the growth of several bacterial isolates including S. aureus, E. coli, Klebsiella granulomatis and P. aeruginosa in the range of 10–17 mm at concentration of 100 µg/ml. It was also demonstrated that AgNPs potentiated the activities of augmentin, ofloxacin and cefixime in the AgNP–antibiotic synergy studies. Similarly, the inclusion of AgNPs as additive in white emulsion paint led to the total inhibition of growth of E. coli, P. aeruginosa, Aspergillus niger and A. fumigatus. To the best of our knowledge, this is the first report of the use of cobweb for the green synthesis of AgNPs. The immense antimicrobial activities of the particles can be explored in the creation of novel products, where it can be used as additive to protect materials against microbial attack.