Abstract

EXTRACELLULAR SYNTHESIS OF SILVER NANOPARTICLES FROM A MARINE ALGA, SARGASSUM POLYCYSTUM C. AGARDH AND THEIR BIOPOTENTIALS

Asha Kanimozhi S, Johnson M*, Chandra Kala P, Shibila T, Revathy I

ABSTRACT

The present study was aimed to optimize the protocol for the synthesis of silver nanoparticles using aqueous extracts of Sargassum polycystum C. Agardh and to evaluate their antibacterial and cytotoxic potentials. The reduction of pure Ag+ ions was monitored by measuring the UV-Vis spectrum of the solution at 200-900 nm using Shimadzu spectrophotometer and the characteristic peaks were detected. FTIR analysis was performed using Perkin Elmer Spectrophotometer system, which was used to detect the characteristic peaks and their functional groups of S. polycystum SNPs. To know the structural characteristics of silver nanoparticles the powder method of diffraction was employed. Antibacterial activity of aqueous extracts and silver nano partciles of S. polycystum was carried out using agar well diffusion method. To know the cytotoxic and anti-cancer potentials, the brine shrimp bio-assay and Trypan blue dye exclusion method was employed. On mixing the S. polycystum aqueous extract with 1mM AgNO3 solution, the colour of the solution changes from pale yellowish brown to dark brown colour which indicates the presence of silver nanoparticles. The AgNP’S synthesized from aqueous extracts of S. polycystum showed the optical peak at 430 nm with the absorption of 0.716. The synthesized silver nanoparticles were capped by proteins and metabolites such as phenolic acid, carboxylic acid and flavonoids. The XRD pattern of S. polycystum AgNPs showed nine peaks at 2θ values of 21.405°, 28.388°, 29.947°, 32.244°, 40.553°, 46.223°, 54.78°, 57.448° and 76.67°corresponding to 208, 509, 149, 1681, 257, 833, 257, 272 and 256 planes of silver respectively. The S. polycytum AgNP’s (100 μl/ml) supplemented cultures demonstrated maximum zone of inhibition against M. margonii (8± 0.3 mm). The silver nanoparticles of S. polycystum demonstrated the highest lethal activity (LC50 502.72 μl/ml) against Artemia salina. The maximum number of cell inhibition (CTC50 188.64 μl/ml) was observed in AgNPs of S. polycystum. Bioefficacy and cytotoxic studies against Artemia salina and DLA Cell lines confirmed that silver nanoparticles of S. polycystum are capable of rendering high antibacterial and cytotoxic activity and hence has a great potential in the preparation of antibacterial and anti-cancer drugs. The synthesized SNP’s improve the therapeutic and medicinal values of S. polycystum.

Keywords: Silver nanoparticles; Seaweeds; Sargassum polycystum; anti-bacterial; Cytotoxicity.