Abstract
Studying of nanoparticle structures is gaining momentum because of their great potential in improving several fields of science such as agriculture. The water soluble fraction of the extracellular polysaccharides (EPS)/matrix of the highly EPS producing cyanobacterium Nostoc commune have been used as a potent reducing and capping agent for green synthesis of silver nanoparticles. The size of these nanoparticles with the EPS coat was found to be in the range of 15-54 nm as analyzed using transmission electron micrographs. Interestingly, after washing the EPS coated silver nanoparticles by ethanol, the size of nanoparticles reduced to less than 15 nm due to the formation of silver oxide nanoparticles and removal of the EPS coat. Silver nanoparticles showed antibacterial properties against Escherichia coli. The minimum inhibitory concentration (MIC) was 0.012 mg/ml while the minimum bactericidal concentration (MBC) was 0.016 mg/ml. The slight difference between the MIC and MBC suggests that such silver nanoparticles act as a potent bactericidal agent against E. coli. Presoaking seeds of crop plants (Sorghum and broad bean) in five-fold MBC of silver nanoparticles (0.08 mg/ml) did not adversely affect the germination of Vicia faba L. and Sorghum bicolor plants. Concomitantly, such fivefold MBC concentration of silver nanoparticles was powerful sterilizing agent for seeds and grains against seed/grain-borne microorganisms. The results showed gradual depletion of the total colony forming units (CFU) in seeds and grains sterilized with silver nanoparticles than those sterilized with chlorine. These results suggest that the water soluble fraction of the extracellular polysaccharides (EPS)/matrix of Nostoc commune can be used as a potent reducing and capping agent for green synthesis of silver nanoparticles and that silver nanoparticles can be used as a potent surface sterilizing agent of seed crops against phytopathogenic fungi.
Highlights
Silver nanoparticles have received considerable attention because of their antimicrobial properties [1]
This study focuses on the green synthesis of metallic nanoparticles of silver using a reduction of aqueous Ag+ ion by the water soluble fraction of the extracellular polysaccharides/matrix of the potent EPS producing cyanobacterium Nostoc commune
The current study focuses on the new synthesis of metallic bionanoparticles of silver using a reduction of aqueous Ag+ ion by water soluble extracellular polysaccharides/matrix of the cyanobacterium Nostoc commune
Summary
Silver nanoparticles have received considerable attention because of their antimicrobial properties [1]. Green synthesis of silver nanoparticles provides an alternative to chemical and physical methods as it is cost effective, environment friendly and does not involve use of costive chemicals. The biologically synthesized nanoparticles are highly useful for biomedical applications Different natural products such as monosaccharides have been used as reducing agents in green synthesis of silver nanoparticles. An interesting example of the biosynthesis of nanoparticles using fungi was that the cell-associated biosynthesis of silver using Fusarium oxysporum was demonstrated by Ahmad et al [10]. These nanoparticles were overall quasi-spherical with size range
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