Preparation And Characterization Of Gold Nanoclusters And Their Biological Effects On Broad Beans

With the widespread use of engineered nanomaterials,researchers have gradually realized that while facilitating life,they may also cause environmental pollution and ecological problems.However,as of now,there are only a few studies involving the interaction between nanomaterials and plants,as opposed to a large number of studies on microbes,cells,and animals related to nanomaterials.Among them,in-depth studies on the absorption and transport laws of nanoparticles in plants and biological toxicity are very scarce.Most of the studies are mainly to observe the adsorption of nanomaterials in vitro and the apparent changes of plants.And the particle size involved in the study is generally large and difficult to penetrate the barrier of the cell wall.For this reason,this experiment intends to use small-diameter gold nanoclusters(Au NCs)composed of only a few dozen atoms as the test materials,with relatively large-diameter gold nanoparticles(Au NPs)as the control,and broad bean as the experimental plant.By measuring the germination index of broad bean,antioxidant system enzyme activity,lipid peroxide content and related biomass,explore the biological effects of nanomaterials on plants.At the same time,fluorescence spectrometer,transmission electron microscope and flame atomic absorption spectrometer were used to observe the absorption and transportation of Au NCs by broad bean seedlings.The micronucleus test results are used to evaluate the toxicity of nanomaterials to plants.It is expected to provide a theoretical basis for the systematic evaluation of plant response and feedback to nanomaterials and other ecological effects.The results are as follows:(1)Au NCs at concentrations of 100 mg/L and above have potential risks to the environment,and Au NCs at concentrations of 300 mg/L and above will affect the mitosis of broad bean root tips(2)The Au NCs treatment basically did not affect the germination of broad bean seeds.Within the experimental concentration range,the general rule of influence on the germination rate,germination potential and germination index of broad bean seeds increased first and then decreased,but there was no significant difference(P>0.05),indicating that the Au NCs solution had no significant effect on the germination stage of broad bean seeds.Au NCs solution has a certain degree of promotion effect on the plant height,main root length and dry weight of broad bean seedlings at low concentration.When the concentration of Au NCs continues to increase,the promotion effect decreases until the inhibition effect occurs.The influence trend of Au NPs treatment group and Au NCs treatment group was basically the same.(3)Physiologically,when the concentration of Au NCs is greater than 100 mg/L,peroxidative damage occurs in broad bean cells.The high concentration of Au NCs increases the content of active oxygen in broad beans.At this time,the antioxidant system takes countermeasures-the activity of antioxidant enzymes is increased to remove excess active oxygen.When the content of active oxygen is too high,it exceeds the regulation of protective enzymes.Range,it will cause oxidative damage to the plant,resulting in the destruction of the cell structure.(4)Both nanomaterials can be adsorbed on the surface of the root tips of broad bean seedlings.Au NCs are more easily absorbed by the root system than Au NPs,indicating that the impact of nanoparticles on plants is restricted by the size of the particle size.Regarding the storage of two kinds of nanoparticles in Vicia faba: the root system is mainly the cell wall,and the ground part is mainly cytoplasm.This shows that the stress feedback of Vicia faba seedlings to the nanomaterials,the root and the ground part of the detoxification mechanism are different,and it is affected by the protection of the plant compartment.The content of gold in the organelles is the least.