Abstract

In the present study we have made an attempt to develop an eco-friendly, cheap and convenient biological (green) method for the synthesis of silver nanoparticles (AgNPs) using the cell extract of the cyanobacterium Nostoc sp. strain HKAR-2. Their anticancerous, antifungal and antibacterial properties were also studied against MCF-7 cells, two fungal strains (Aspergillus niger and Trichoderma harzianum) and two plant bacterial strains (Ralstonia solanacearum and Xanthomonas campestris), respectively. The structural, morphological and optical properties of green synthesized AgNPs were determined by UV-VIS spectroscopy, Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction, transmission electron microscopy selected area electron diffraction (TEM-SAED) and scanning electron microscopy (SEM). Spectroscopic analysis showed the peak at 419 nm due to the reduction of AgNO3 into silver ion by cyanobacterial extract indicating surface plasmon resonance (SPR) of the synthesized AgNPs. The XRD pattern of AgNPs showed the characteristic Bragg peaks at (111), (200), (220) and (311) facets of the face centre cubic (fcc) confirming their crystalline nature. FTIR analysis revealed that proteins and amino acids are responsible for the reduction of AgNO3 into Ag+ as well as for the stability of nanoparticles. Zeta potential confirmed that the charge on the nanoparticles is 1.80 mV which indicates the presence of stable nanoparticles. The results of SEM and TEM confirmed the large agglomerated shape of AgNPs with size ranging between 51-100 nm. The AgNPs showed a dose-dependent cytotoxic activity against human breast cancer MCF-7 cells with IC50 of 27.5 µg/ml. They also exhibited excellent antibacterial and antifungal activities.

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