The Study On Toxicity Of Fe₃O₄ Nanoparticles With As Or Pb Adduct And TiO₂ Nanoparticles To Cells And Bacteria

There are many kinds of pollutants in the environment,including heavy metal pollutants and metal oxide nanoparticles.Considering the different reaction between pollutants and organisms,the additional toxicity caused by should be studied in details.It is impotant to study on the environmental risk of metal oxide nanoparticles and their heavy metal addcut in the environment and toxic effects on health.We studied the biological toxicity effects of metal oxide nanoparticles and their heavy metal addcut by bacterial and cell models,and explored the possible mechanisms of their toxicity,which is great significance to understand and evaluate its potential impact on water environment,animal and human health.TiO₂ nanoparticles?TiO₂NPs?and Magnetite nanoparticles?MNPs?are two kinds of metal oxide nanomaterials,which are widely used.We use MNPs with arsenic?As?or lead?Pb?adduct?MNPs-As or MNPs-Pb?as the representative of the adduct of metal oxide nanoparticles and heavy metals,with human embryonic kidney cells?HEK293?and rat kidney cells?NRK?as a model to study the cytotoxic effect of adduct on human cells and animal cells.The studies are as follows:?1?With different culture methods?adherent culture and suspension culture?,we studied the toxic effects of TiO₂ NPs mass concentration,particle size and surface area on the different forms of bacteria,and further discussed the possible mechanism the toxicity mechanism of TiO₂ NPs.?2?We used MNPs-As as the representative of the adduct of metal oxide nanoparticles,human embryonic kidney cells as model cells,SOD enzyme as the representative of oxidative stress indicators.With corresponding concentration of arsenic and MNPs as comparison,we determined cell viability,uptake of the nanoparticles,cell morphology,oxidative stress,cell apoptosis level,to study effects of MNPs-As on physiological cell function and its possible toxic effect.?3?With the corresponding concentration of lead and MNPs as comparison,we studied the influence of MNPs-Pb on rat kidney cells and its possible toxic effects by measuring cell viability,cell morphology,cell uptake of nanoparticles and apoptosis level.The results obtained are as follows:?1?Under non light conditions and different cultivation modes,the toxic effects of TiO₂ NPs on bacteria were significantly different.Under the same conditions,TiO₂NPs had more toxic effects on bacteria in suspension culture than in adherent culture.Adherent bacteria reduced the toxicity of nanoparticles by secreting extracellular polymeric substances?EPS?and forming biofilms.In suspension culture,bacteria were difficult to form biofilms and reduce the toxic effect of TiO₂ NPs.The surface area of TiO₂ NPs that can directly contact with bacteria was positively correlated with the toxicity of TiO₂ NPs to bacteria.Smaller TiO₂ NPs has more chances to contact directly with bacterial.The small TiO₂ NPs had more toxic effects on the adherent culture bacteria than larger nanoparticles,because smaller TiO₂ NPs may readily transpot between biofilm and EPS than larger nanoparticles.?2?Arsenic could lead significantly the cell viability inhibition,change in cell morphology and density,decrease of SOD activity in cells,oxidative damage and cell apoptosis,which the toxic effect was dose-dependent.MNPs-As could not significantly change cell morphology and cell density.The cell uptake of MNPs-As could not significantly effect the cell because location and no"Trojan horse"effect.There were slightly oxidative stress,cell apoptosis level increasing and cell viability inhibition.It was inferred that MNPs-As may have not significant toxic effects on cells,compared with the corresponding concentration of arsenic,The toxic effect of MNPs and arsenic on human embryonic kidney cells was not synergistic.?3?Lead could cause significant inhibition of cell viability,significant change in cell morphology,and significant cell apoptosis,which had significant toxic effect on cells.MNPs-Pb could not lead to significant changes in cell density and morphology.It made the early apoptosis of cells increase slightly and no effect of promoting apoptosis.Due to the large particle size and rare uptake by cells,it was difficult to cause significant toxic effects.MNPs-Pb may have not significant toxic effects on rat kidney cells,compared with the corresponding concentration of lead.It was found that there was not synergistic effect of MNPs and lead on the renal cells of rats.