Cytotoxicity Of Plant-mediated Metal Nanomaterials

Nanomaterials are new materials with broad application prospect.However,their negative environmental impacts and ecological effects during their production and use has drawn wide attention.As a matter of fact,nanomaterials are considered as a new type of pollutant,which has been confirmed that nanomaterials would exert a series of biological toxicity from a growing number of studies.Biological method is an emerging environment-friendly method for the synthesis of nanomaterials,which has the advantages of non-toxic,low-cost,readily available and mild reaction conditions.Hence,biological method has attracted tremendous interests in recent years.However,there are still less studies on the bio-toxicity of bio-synthesized nano-materials(Bio-NPs),the key factors related to their bio-toxicity,and the mechanism of the toxicity.Hence in this paper,to better understand the bio-toxicity of Bio-NPs,Ag and Au nanoparticles were synthesized by plant extracts and applied to toxicity assessment by cytotoxicity test.The influence of Bio-NPs diameters,the biomass type used and different mental on the biological toxicity were the focus of this study.The difference of cytotoxicity of nanomaterials synthesized by chemical and biological methods was also compared.Finally,a possible toxicity mechanism of Bio-NPs was proposed.The plant extracts from Cinnamomum camphor a(L.)Presl.,Scutellaria baicalensis Georgi,and Cacumen Platycladi were adopted as reducing agents to synthesize the gold and silver nanomaterials with different particle sizes.L02 and HEK,which is the healthy cells from human liver and kidney,respectively,were used as the subjects in cytotoxicity test.Exposure time,particle size of nanomaterials,different metal NPs,and different plant extracts on the biological toxicity of Bio-NPs were investigated through the cell proliferation experiments,assay of apoptosis and the detection of reactive oxygen species(ROS)in the cells.The results showed that the bio-toxicity of Bio-NPs to L02 and HEK cells was time-and dose-dependent when the exposure concentration of Bio-NPs was between 0-100 ?g·mL-1 and the exposure time was between 0-48 h.The cytotoxicity of 30-Au-CC was significantly lower than that of 30-Ag-CC when the exposure time was 24 h and the concentration of 100 ?g·mL-1.This was mainly due to the release of metal ions from 30-Au-CC resulting in the lower cytotoxicity.FT-IR spectra indicated that the reducing components in the plant extract are closely related to the bio-toxicity of Bio-NPs,more types of reducing groups usually lead to the smaller the biological toxicity.15-Ag-SG,15-Ag-Chem and 15-Ag-Chern@PEG(15-Ag-Chem coated with SH-PEG,which is a kind of common stabilizers)were chosen as the nanomaterials.L02 and HEK cells were still used as the subjects to explore the cytotoxicity of the three kinds of nanoparticles by cell proliferation,apoptosis,intracellular ROS detection,western blotting experiments.When the exposure concentration was 40 ?g·mL-1 and the exposure time was 24 h,15-Ag-SG exerted lower than 15-Ag-Chem and 15-Ag-Chem@PEG due to the more reducing group species.The cell viability was 82.82%,39.77%and 25.86%respectively for L02 cells,and the cell viability was 80.37%,5.89%,and 2.00%respectively for HEK cells.The plant material had a weakening effect on the biological toxicity of nanomaterials,and the weakening effect increased with the concentration of the plant material.Western blotting showed that,compared with 15-Ag-Chem@PEG and 15-Ag-Chem,the changes in expression of key albumins Perk,eIF2a and ATF4 in endoplasmic reticulum stress exposed to 15-Ag-SG were the smallest,while the 15-Ag-Chem treatment group caused the greatest change.According to the expression of endoplasmic reticulum stress-related protein in L02 cells and HEK cells after treated with 15-Ag-SG,the mechanism of toxicity of Bio-NPs is proposed as following:Bio-NPs first induce cell oxidative stress after entering the cell,and then ROS attack intracellular free sulfhydryl groups and activate the endoplasmic reticulum stress,and ultimately leading to the apoptosis.