A Study On The Damage Mechanism Of Polystyrene Microplastic/Tetracycline Complex On AGS Cells

Microplastics,the plastic fragments with a size less than 5 mm,have been attracted widely attention as a novel contamination,have the features of small size and large specific surface area,many contaminations such as heavy metals,persistent pollutants and antibiotics can easily attach to their surface.Antibiotics have received much attention as one of contamination.So far,we still know little of the damage mechanism of microplastics to human body.The combined pollutants comprised of microplastics and contaminations can be consumed by human through the food chain.Once they enter the body,they can damage human health.However,Therefore,this research is aimed to investigate the effect of polystyrene microplastics(PS-MPs),polystyrene nanoplastics(PS-NPs)and the combine effect of PS-MPs and tetracycline(TC),PS-NPs and TC,respectively,on human gastric cancer(AGS)cell,and to provide the evidence of microplastics cytotoxicity.The results were presented as following:(1)Synthesis of PS-MPs and PS-NPs.The emulsion polymerization method was used to prepare PS-MPs and PS-NPs,and the sizes of them was detected by SEM.The homogeneous particles with different sizes were obtained by changing the ratio of styrene monomer and initiator AIBA.The experimental results showed that PS-MPs were prepared at 55 °C,10% styrene monomer and 0.3% AIBA;and PS-NPs were obtained at 90 °C,1% styrene monomer and 0.0005% AIBA.(2)The adsorption mechanism of TC on the surface of PS-MPs and PS-NPs.It confirmed that the liner fitting was well as TC concentration ranging in 0.5-50 mg/L.The adsorption kinetics was employed,and PS-MPs and PS-NPs adsorption different concentrations of TC reached equilibrium at 360 minutes,the experiment results showed that the equilibrium adsorption capacities of PS-MPs and PS-NPs were 23.573 mg/g and 28.980 mg/g,respectively.60 nm PS-NPs have a proportional relationship with TC concentrations range in 1,5,10,50,100 mg/L,and have a stronger positive correlation of adsorption capacity to TC concentrations of 1,5,10,50,100 mg/L than 500 nm PS-MPs.Adsorption kinetics was suitable for pseudo-first-order model.(3)The damage mechanism of PS-MPs and PS-NPs exposing to AGS cell was researched.Cell viability was decreased by 60 nm PS-NPs and 500 nm PS-MPs using MTT method.And then,the ROS level was detected by DCFH-DA probe,and the results showed that compared with 500 nm PS-MPs,ROS was apparently influenced by 600 mg/L PS-NPs.Moreover,the mitochondrial membrane potential(?? m)was detected by JC-1 probe,and the results showed that PS-MPs and PS-NPs could decrease the ?? m.Comet assay was used to assess DNA damage and the results showed that DNA was damaged by 60 nm PS-NPs and PS-TC NPs,500 nm PS-MPs and PS-TC MPs,and 60 nm PS-NPs damaged DNA more serious than 500 nm PS-MPs.Furthermore,Western blot was utilized to detect the PS-MPs and PS-NPs on apoptotic-related proteins and signal pathway,and the results showed that PS-NPs,PS-MPs could influence the expressions of bax and bal-2,and Akt-m TOR signal pathway was also actived.In summary,500 nm PS-MPs and 60 nm PS-NPs were prepared using emulsion polymerization method in the study.The adsorption capacity of PS-MPs and PS-NPs to TC was positive correlation to TC concentrations.Adsorption kinetics results were suitable for pseudo-first-order model.Furthermore,PS-NPs and PS-MPs caused AGS cell damage,intracellular ROS increasing,DNA damage,?? m deceasing,apoptosis protein overexpressions and Akt-m TOR signal pathway activating.All experiments on the cytotoxicity of PS-MPs and PS-NPs complexed with TC on AGS were larger than those group only exposing to PS-MPs and PS-NPs.It seems that 60 nm PS-NPs have more toxic on AGS cell comparing with 500 nm PS-MPs.