Environmental Toxicology Of Silver Nanoparticles And The Potential Application

Nanosilver has become one of the most widely used and commercialized metal nanomaterials on the market at present due to the well antibacterial,catalytic,optical,superconducting properties and properties.Extensive production and wide application of nanosilver increases the chances of its release to the environment,and at the same time,increases unknown risks to the environmental microorganism.Therefore,the environmental risk of nanosilver is attracting a lot of attention.Only by clarifying the interaction manner and mechanism between nanosilver and environmental microbiology,can we fundamentally understand the toxicity of nanosilver and take corresponding measures to prevent the occurrence of environmental damage.This paper examines various silver nanoparticles toxicity mechanism to bacteria and fungi,environmental organic ligands and inorganic anions on the toxicity of silver nanoparticles and the influence of "Hermesis effect";explores the effect of environmental sulfur source on silver nanoparticles biological toxicity and the"Toxicity to Activation" transformation effect,putting forward the possibility of application of silver nanoparticles;systematically studies the migration behavior of silver nanoparticles in biofilm,biological toxicity of biofilm,and oxidative stress;looks for the practical application of silver nanoparticles in environmental detection and control.In this paper,the specific research works and achievements can be summarized as the following five aspects:The first section describes the microbial cell toxicity of silver nanoparticles and its related mechanism.Two different silver nanoparticles PVP-AgNPs and Citrate-AgNPs was prepared and the toxicity on E.coli and P.chrysosporium was determinated.The results can be concluded as follows:(1)In a certain concentration,silver nanoparticles has inhibitory effect on microorganisms.(2)When concentration of silver nanoparticles below the value,it will stimulate microbial growth but not inhibition.Compared with the blank control,0.34 mg/L PVP-AgNPs stimulate E.coli survival by 129.9%;1,2,and 3 mg/L Citrate-AgNP salso makes survival rate of P.chrysosporium higher than the control group.The second section focused on the environmental cysteine and inorganic anions effect on silver nanoparticles toxicity and "Hermesis effect".Through adding in the environmental related groups such as cysteine and inorganic adion(S2-,Cl-and PO43-)in toxicity test,the impact of these groups on toxicity of silver nanoparticles was determinated.The results showed that cysteine and inorganic anions can complex with silver ions on the surface of silver nanoparticles,which affect the behavior of silver nanoparticles toxicity.High concentrations of silver nanoparticles was toxic to microbes,however,cysteine and sulfur ions addition can induce the "Hermesis effect".This effect causes the transfer of silver nanoparticles to stimulate microbes from inhibition.Because of the weak ability in combination of silver ions,Cl-and PO43-will not induce the "Hermesis effect" of silver nanoparticles.The effect of environmental groups on silver nanoparticles is associated with sulfuration rate.The third section describesthe specific studies of silver nanoparticles on P.chrysosporium activity undersulfur sourceand its control applications.Chemical synthesis and biosynthesis of silver nanoparticles were prepared,and examines two silver nanoparticles effect on fungi and bacteria,discussed two kinds of different sulfur source organic sulfur source thioacetamide(TAA)and inorganic sulfur source sodium hydrosulphide(NaHS)effect on the toxicity of silver nanoparticles.The results indicateenvironmental sulfur source includingorganic sulfur thioacetamide and inorganic sulfur NaHS can affect toxic behavior of silver nanoparticles,prompte transfer of the best activation concentration toward the high concentration.The initial toxic silver nanoparticles at high concentration converted to stimulate microbial growth.The fourth part examines the sulfur source on silver nanoparticles migration,transformation in water treatment of biological membrane and toxicity to biological membrane.The biofilm was created by culturing P.chrysosporium in the model and waterfall filtering method.Explore the migration,transformation,and retained number of silver nanoparticles in biofilm in each layer,and the toxicity on the biofilm layer.The result show(1)both types of silver nanoparticles tested easily penetrated the P.chrysosporium biofilm and remained mostly in the bottom layer 1.6-2.0 cmwhen cysteine was present.In contrast,both types of silver nanoparticles remained in the surface layer 0-0.4 cm in an aggregated form in the presence of Na2S.(2)An obvious particle-specific toxicity to the film was observed,despite the inhibited Ag+release in cysteine-abundant surroundings.In the presence of Na2S,the toxicity of both types of silver nanoparticles was completely inhibited.The fifth part explores detection of race mercury and stability with silver nanoparticles.A rapid sensitive method of mercury ion in environmental conditions was proposed.Silver nanoparticles can react with Hg2+,observed by a decrease in the UV-vis absorption.This decrease in the UV-vis absorption was proportional to the concentration of Hg2+.Under optimized conditions,the sensing system exhibited alinear range of 5.0 × 10-10 to 1.2 × 10-7 M for Hg2+,with a detection limit of 0.31 nM in buffer.At the same time,the probe can be generated with mercury ions by silver amalgam precipitation,won't cause new silver pollution to the environment.The probe also can be used as the stabilizer of mercury in the environment,avoiding the happening of mercury pollution in the environment.This paper clarified the cell toxicity and mechanism of silver nanoparticles,and impact of cysteine and environmental related anions on their toxicity;revealed the interaction mechanism of different sulfur source on "Hermesis effect",and the migration,distribution regularity in biofilm and toxicity to the biofilm;explored the identification and stability of race mercury using silver nanoparticles.Related research results help us to understand the environmental dangers of silver nanoparticles,and provide technical and theoretical support for wastewater treatment containing silver nanoparticles.