Toxicity And Mechanism Of Lead-loaded Ultrafine Carbon Black On Blood Transporter And Mouse Nephrocyte

Atmospheric particulate matter(PM)is the main pollutant affecting urban air quality at present.The concentration and size of PM will directly affect the morbidity and mortality of urban residents,and the adverse effects caused by smaller PM is greater.The number concentration of ultrafine particles(UFPs)occupy an important part in atmospheric particles.Exposure to UFPs could cause lung inflammation and respiratory diseases,and even induce damages to other tissues and organs by crossing the lung-blood barrier.With the small particle size and large specific surface area,UFPs as the complex environmental pollutants,are easy to adsorb a variety of pollutants such as heavy metals.After UFPs enter the organism,the toxic effects produced are the result of the combined action of various components.However,there are few studies on the toxic effects and mechanisms of each components of UFPs.Ultrafine carbon black has the single component and is similar to the morphology and structure of-UFPs,it could be used as the substitute for the biological study of UFPs.Heavy metal lead is a common pollutant and is easily adsorbed by UFPs.It is very common for UFPs loaded with lead to enter organisms,and its toxic effects and mechanisms are still unclear Therefore,we systematically studied and comparatively analyzed the toxicity effects of ultrafine carbon black before and after lead loading on mouse nephrocytes and two protein:human serum albumin(HSA)and bovine hemoglobin(BHb),at the cellular and molecular level.The main research content of this article includes the following parts:(1)Modified ultrafine carbon black(UFCB)was obtained by using ozone oxidation to improve the dispersion stability of ultrafine carbon black in solution.The modified ultrafine carbon black was applied to the adsorption experiment of heavy metal lead,and a lead-loaded ultrafine carbon black(UFCB-Pb)with a lead loading of 0.65 mg/mg was prepared(2)Mouse nephrocytes were selected as target cells.The effects of UFCB,UFCB-Pb and Pb(Ac)2 on the oxidative stress of mouse nephrocytes were explored and compared at the cellular level.The results showed that the exposure of the three pollutants significantly reduced the cell viability of mouse nephrocytes.When the concentration of the pollutants reached 8 mg/L,the cell viability of mouse kidney cells decreased by more than 30%.The presence of the three pollutants significantly increased the production of intracellular reactive oxygen species(ROS).When the concentration of the pollutants reached 8 mg/L,the relative levels of intracellular ROS production reached 141%(UFCB),175%(UFCB-Pb)and 227%(Pb(Ac)2).As the concentrations of the three pollutants increased from 0 mg/L to 8 mg/L,the intracellular MDA content showed a significant upward trend,which could reach 125%(UFCB),134%(UFCB-Pb),and 167%(Pb(Ac)2).The intracellular catalase(CAT)activity increased,and its relative activity level exceeded 130%.The superoxide dismutase(SOD)activity decreased,and its relative level was below 85%.It is concluded that the three pollutants of UFCB,UFCB-Pb and Pb(Ac)2 induced the oxidative stress effects of mouse nephrocytes and caused some oxidative damage.By comparison,the oxidative stress effects of Pb(Ac)2 in mouse nephrocytes were the most obvious,and UFCB-Pb could be easier to induce oxidative stress in mouse nephrocytes than UFCB(3)Human serum albumin and bovine hemoglobin were selected as target molecules.At the molecular level,the interactions of UFCB,UFCB-Pb,and Pb(Ac)2,with proteins were studied using technologies such as ultraviolet-visible absorption spectra,fluorescence spectra,and circular dichroism spectra.The results of HSA showed that with the exposure concentrations of the three pollutants increase from 0 mg/L to 8 mg/L,the HSA skeleton structure became tighter.The three pollutants interacted with HSA to form a complex,which increased the particle size of the experimental system.UFCB had a fluorescence quenching effect on HSA,while UFCB-Pb and Pb(Ac)2 had a fluorescence sensitizing effect on HSA.The presence of UFCB-Pb slightly changed the secondary structure of HSA,reduced the a-helix content by 2.6%and reduced the ?-sheet content by 2.2%.The secondary structure of HSA was not significantly changed by UFCB and Pb(Ac)2.The results of BHb showed that the exposure of the three pollutants tightened the BHb skeleton structure,and made BHb have a fluorescence sensitization effect,and reduced the content of a-helix in the secondary structure of BHb.When the pollutant concentration reached 8 mg/L,the a-helix content in BHb decreased by 3.6%(UFCB),7.3%(UFCB-Pb),and 2.8%(Pb(Ac)2).UFCB and UFCB-Pb exposure increased the particle size of the experimental system,and Pb(Ac)2 exposure decreased the particle size.Through comparison,it could be found that the interaction effects of UFCB,UFCB-Pb and Pb(Ac)2 with proteins are not the same,and the difference in the effects of UFCB-Pb chould be due to the Pb adsorbed by UFCBIn this thesis,a method for ultrafine carbon black surface modification and adsorption of heavy metal lead was established.The toxic effects of three pollutants,UFCB,UFCB-Pb and Pb(Ac)2,were studied and compared at the cellular and molecular levels.The results showed that compared to UFCB,UFCB-Pb had more toxic effects on organisms at the molecular and cellular levels.This paper provides the biological safety information of UFCB-Pb,and provides a scientific basis and research methods for evaluating the toxic effects of UFPs with complex components.