Physicochemical characterisation and ecotoxicological assessment of nano-silver using two cyanobacteria Nostoc muscorum and Plectonema boryanum

Abstract

The rapid expansion of nanotechnology has led to the use of nanomaterials in various consumer products. Among these nanomaterials, nano-silver has gained considerable attention as an excellent candidate due to its unique physical and chemical properties. However, studies related to their effects on the ecosystem are still insufficient. Thus, the present study was designed to explore in length the toxic effects of nano-silver on Nostoc muscorum and Plectonema boryanum in terms of dose-dependent cellular growth, cell viability, bioaccumulation/biodistribution and changes in protein profile. The exposure to nano-silver resulted in 8–9 times less reduction in cell viability as compared to silver nitrate, suggesting the formation of aggregates in test medium and low release of silver ions from nano-silver. Morphological changes under stress were studied by scanning electron microscopy, and corresponding elemental silver was monitored by energy-dispersive X-ray spectroscopy. Significant uptake and bioaccumulation/biodistribution of both forms of silver were elucidated by atomic absorption spectroscopy and transmission electron microscopy, respectively. This study demonstrated that silver nitrate was more toxic as compared to nano-silver and both exerted toxic effects in a dose- and species-specific manner. The present study suggests that observed toxicity of nano-silver might be due to the silver ions released from nano-silver. Thus, the release of silver from various consumer products in the environment should be controlled and carefully monitored at regular interval.