Study On The Toxicological Effects Of Anatase TiO₂ Nanoparticles On Brachionus Calyciflorus

Brachionus calyciflorus Pallas belongs to Rotifer,Monogononta,Ploima,Brachionidae,and its life history has alternate generations.In recent years,due to its small size,short life cycle,easy cultivation in laboratories,more sensitive life indicators for toxicity evaluation,and its important role in aquatic ecosystems,rotifers have been studied internationally as ecotoxicology the test animals has become a hot spot,is considered the most meaningful study of nanoparticles tiny invertebrate herbivores influence on the indicator species.Nano-sized TiO₂,also known as titanium dioxide.The diameter is below 100 nm,and the appearance of the product is white loose powder.With anti-line,antibacterial,self-cleaning,anti-aging properties,widely used in many consumer products and the decontamination process of air,soil and water.Due to the negative impact of the emission of nanoparticles on the ecosystem,its pollution has become one of the most concerned environmental issues.nano-scale TiO₂ is a nanomaterial that has attracted more attention at present.In this experiment,Brachionus calyciflorus was used as a test organism in fresh water,and the purpose was to explore the effects of TiO₂ nanoparticle solutions of different sizes and different concentrations on rotifer population,lifespan and reproduction.Furthermore,the effects of different TiO₂ nanoparticle solutions on some antioxidant enzyme activities and feeding conditions in rotifers were studied,which provided theoretical basis for promoting Brachionus calyciflorus as a model animal for the study of nanoparticle ecological toxicology,and experimentally studied TiO₂Toxicity of nanoparticles to rotifers and potential risks to aquatic ecosystems.The main experimental results are as follows:1.Effects of different sizes of anatase TiO₂ nanoparticles on population parameters of Brachionus calyciflorusThe experimental temperature was 25±1?,the light was 4000lx,and the day length ratio?L:D?was 16:8.A control group and TiO₂ nanoparticle solutions with 5,50,and 200 nm diameter particles?EPA configuration?were set.After exposure treatment with four concentration gradients of 0.5,1,10,and 20 mg/L,the population dynamics,population growth rate,and population density of Brachionus calyciflora were counted.The experiments show that when the diameter of TiO₂ nanoparticles was When the concentration was 5 nm and the concentration was 20 mg/L,the difference between the groups was the most significant.In this group,the maximum population density was reached on the 6th day,and the maximum population density was 21.6±4.3 ind/m L,which was about 63.14%lower than the control group?the maximum population density was 58.6±3.98 ind/m L?.The maximum population growth rate of this group was 0.73,Which was about 11.0%lower than that of the control group?the maximum population growth rate is 0.82?.The experimental results showed that TiO₂nanoparticles can inhibit the growth of Brachionus calyciflorus population and reduce the environmental capacity of the population.The inhibition effect is positively related to the concentration of nanoparticles in the TiO₂ nanoparticle solution and negatively related to the size of the particles.2.Effects of different sizes of anatase TiO₂ nanoparticles on lifespan and reproduction of Brachionus calyciflorusIn the experiment,the average lifespan,pre-reproductive stage,average number of eggs carried,reproductive curve and average number of progeny were counted at the same experimental concentration and diameter.Through the two-factor analysis,with the exception of the pre-reproductive period,as the concentration increased and the particle size of the nanoparticles decreased,the average lifespan,average number of eggs carried,reproductive curve,and average number of progeny of each treatment group were affected to varying degrees inhibition.The pre-reproductive stage was only related to the concentration of the nanoparticle solution.When the concentration of the solution was higher,the pre-reproductive stage of rotifers has an earlier trend.Among them,the diameter of TiO₂ nanoparticles was 5 nm and the concentration is 20 mg/L.The average lifespan of rotifers was 71.0±4.88 h,which was 49.29%less than the control group?140.0±5.10 h?;The pre-reproductive period is 20.8±1.52 h,The control group?22.8±1.87 h?was 9.1%earlier;the average egg carrying capacity was 5.9±0.82,a 63.12%decrease compared to the control group?16.0±1.20?;the average number of offspring was 5.4±1.13,compared with the control group?9.6±1.80?decreased by 43.75%,the difference was particularly significant.Experiments had showed that TiO₂ nanoparticles not only affect the population growth of rotifers,but their toxicity also had a negative effect on the life and reproduction of rotifers.Increasing exposure time will also increase the toxicity of TiO₂ nanoparticles to rotifers.3.Effects of different sizes of anatase TiO₂ nanoparticles on CAT and SOD enzyme activities of Brachionus calyciflorusAfter being exposed to different diameters and different sizes of TiO₂ nanoparticle solutions for 24 hours,the CAT and SOD enzyme activities were measured in vivo.The data showed that the activities of CAT and SOD enzymes increased with the increase of the concentration of TiO₂ nanoparticle solution,and decreased with the increase of the particle size of the nanoparticle,enzyme activity values were increased compared to the control group.Experiments showed that the addition of nanoparticles activates the activity of CAT and SOD enzymes.The activity value of CAT and SOD enzymes in rotifers was particularly significant in small particle size and high concentration solutions.Compared with the control group,the CAT enzyme activity value increased by 81.14%,and the SOD enzyme activity value increased by 52.31%.Experiments showed that within a certain concentration range,TiO₂ nanoparticles cause rotifers to produce oxidative stress,and the body's active oxygen ROS significantly increases.More antioxidant enzymes were needed to clear the body's active oxygen ROS,which was directly related to defense mechanisms.4.Effects of different sizes of anatase-type TiO₂ nanoparticles on feeding of Brachionus calyciflorusBrachionus calyciflorus was exposed to TiO₂ nanoparticles with different diameters at a concentration of 10 mg/L,and images were taken for 24,48,and 72 h.During the72 h experimental period when no algae food was provided,TiO₂ nanoparticles of various diameters both were partially ingested by rotifers.In the experimental group,during the same time from 24 h to 72 h,the accumulation of rotifer's masticator,intestine and stomach had different degrees of nanoparticle accumulation than the control group,the phenomenon in the 5 nm experimental group was the most obvious,and the accumulation in the 200 nm experimental group was the lightest.We found that small-sized nanoparticles can even penetrate the intestinal wall into the body cavity,while larger-sized nanoparticles were mainly restricted to the intestine and stomach.TiO₂ nanoparticles cannot be completely excreted in the rotifer's body.Accumulation in the body will affect the rotifers'normal intake of algae and other nutrients,rotifer individuals cannot obtain sufficient nutrition,and their life span and reproduction were inhibited,which will affect the establishment of the population.Our experiments showed that the accumulation of nanoparticles in rotifers is positively related with the time of the experiment,negatively related with the diameter of the experimental nanoparticles,and the experimental phenomenon was significant.