Study On The Interaction Between Polystyrene Nanoplastics And Two Brominated Flame Retardants And Human Serum Albumi

As an emerging environmental contaminant,nanoplastics（NPs）have attracted more and more attention for their potential risks to the environment and human beings.Brominated flame retardants（BFRs）are another contaminant of widespread concern,commonly used as plastic additives,which are abundant in the environment and can have adverse effects on organisms.Due to its hydrophobicity,BFRs can be adsorbed on the surface of NPs to form complex pollutants,resulting in combined toxic effects on environment or organisms.NPs and BFRs,which are widely present in the environment,can be transferred to organisms through the respiratory and digestive tracts as well as the skin,and bind to proteins in the blood,change the structure and physiological function of proteins,thus affecting human health.Proteins play an important role in both the environment and organisms,so it is important to study the interaction of NPs and their complex pollutants with BFRs with human serum albumin（HSA）and their effects on protein function to understand the toxic effects of NPs.In this paper,polystyrene nanoplastics（PSNPs）,tetrabromobisphenol A（TBBPA）and tetrabromobisphenol S（TBBPS）were selected as the research objects.The interaction between PSNPs and HSA and the effect of the presence of PSNPs on the interaction between TBBPA/TBBPS and HSA were studied at the molecular level.The main research contents and findings are as follows:（1）Multispectral technique and dynamic light scatterin（DLS）method were used to study the interaction between PSNPs and HSA and its effects on the protein function under two physiological acidity conditions（p H 4.0 and 7.4）.Spectral analysis showed that PSNPs and HSA formed a complex through dynamic and static binding quenching mechanism.Under acidic p H 4.0,the binding of PSNPs and HSA was stronger,resulting in significant fluorescence quenching.Electrostatic interaction drives the binding of HSA and PSNPs,which affects the surface properties and stability of HSA-PSNPs complex.In addition,the binding of PSNPs interfered with the conformation of HSA,and then inhibited the esterase activity of HSA,which was more obvious under acidic p H conditions.（2）The interaction of pristine polystyrene（PS）、carboxy-modified polystyrene（PS-COOH）、amino-modified polystyrene（PS-NH₂）NPs with HSA and its effects on protein conformation and physiological activities were investigated under simulated physiological environment conditions.Fluorescence experiments showed that the combination of PS,PS-COOH and PS-NH₂ with HSA induced the quenching of the intrinsic fluorescence of HSA,and its mechanism was dynamic and static mixed quenching.Since PS-COOH binds closer to tryptophan residues,the fluorescence quenching is most obvious.The DLS results showed that the interaction between HSA and three PSNPs resulted in different particle size changes,and the binding of HSA promoted the dispersion of PS-COOH.The presence of PS,PS-COOH and PS-NH₂ can affect the conformation of HSA.The esterase activity results showed that PS,PS-COOH and PS-NH₂ all caused a decrease in the esterase activity of HSA,and the decrease caused by PS-COOH was greater.（3）The effects of the presence of PSNPs on the interaction between TBBPA/TBBPS and HSA under simulated physiological and natural water environment were studied by spectroscopy combined with molecular docking technology.Studies have shown that both protein adsorption and binding of BFRs are affected by the p H value and structure of BFRs.At p H 7.4,HSA adsorbed on NPs particles would bind fewer BFRs,while at p H 4.0,the binding of BFRs was not affected.The spectral study showed that with the decrease of p H value,the binding efficiency of TBBPS and HSA increased,while the binding efficiency of TBBPA was inhibited.There were different binding modes between TBBPA/TBBPS and HSA,which did not significantly affect the structure of proteins.The results showed that p H value and chemical heterogeneity of BFRs were important factors affecting the interaction of HSA,BFRs and PSNPs.In addition,different types of electrolytes also have a great impact on the interaction.The presence of ions can lead to changes in the surface electrostatic properties and conformation of HSA,thus affecting the binding behavior of HSA with BFRs and PSNPs.