Effects Of Titanium Dioxide Nanoparticles On Intestinal Commensal Bacteria

Rapid development of nano science and technology in recent years makes the nano materials widely used in people's daily life.Titanium dioxide nanoparticles(TiO2)is considered non.-toxic to human body and thus has been adopted in purification of air and water,food packaging,sunscreen cosmetics production,and many other applications.Wide use of titanium dioxide nanoparticles makes it very easy absorbed into the human intestine through food,air or water.Human intestinal symbiotic has plenty of intestinal flora and the normal symbiotic bacteria play an important role in the host energy and metabolic balance.Once they are in disorder,host health is likely affected and it results in disease.Titanium dioxide photocatalytic bactericidal effect has been applied in practice.Once the titanium dioxide nanoparticles enters the human body,where they are not exposed to ultraviolet,it will effect intestinal bacteria and the side effects to the human body remain to be researched.Drosophila as a model of biological experiments have the same conservative signaling pathway to mammals and have less drosophila intestinal bacteria class number.Therefore they are good to use for research.The midgut of laboratory-reared drosophila harbors five major commensal bacterial species,Commensali bacterintestini,Acetobacterpomorum,Gluconobactermorbifer,Lactobacillus plantarum,and Lactobacillus brevis.Our experiment mainly aimed at three of these intestinal flora,Acetobacteria,Lactobacilli and Enterobacteria,to examine the effect of nanometer titanium dioxide on gut bacteria.In vitro,we use titanium dioxide nanoparticles to deal with the intestinal bacteria that isolated from fruit flies,and we observed that high concentration(2 mg/ml)of titanium dioxide has the sterilization effect,and the report of titanium dioxide sterilization mechanism shows it can absorb a certain wavelength ultraviolet light wave to make its surface to produce super oxide,super oxide effects on bacteria and killing bacteria.It is also possible that the titanium dioxide nanoparticles has the small size effect,making it easier to penetrate the cell membrane,enter the cells,destroy the cellular structure and even the genetic material,eventually kill bacteria.Because our experiment is away from light,we can rule out photocatalytic bactericidal effect and prove that in the absence of photocatalytic in vitro,titanium dioxide nanoparticles have antiseptic effect.Then we performed the experiment inside flies,through feeding the drosophila larvae and adult titanium dioxide nanoparticles,intestinal dissection,counting the number of bacteria.We found no obvious difference with the control and the number of bacteria is not affected.As known,flora imbalance can cause the host body lesions.We didn't see the effect of titanium dioxide to the drosophila in our experiment so we assume that the fruit body health also should not be affected.In our following efforts we test weight,growth and development situation,lipid metabolism and climbing index of flies.We hope that these physical index can give us a direct look at the nanometer titanium dioxide effection on the body.Our results validate our speculation and show that these indicators has no difference with control.Our experiments proved that the body environment is better than in vitro in protecting the intestinal bacteria from titanium dioxide poisoning.Toxicity of nano titanium dioxide has been demonstrated in mice.A certain concentration of nano titanium dioxide can cause mouse liver,lungs,tissues and organs such as brain cortex injury.Because our experiment took only two concentrations,and the flies were fed 5 days with nanometer titanium dioxide,there is no any adverse effects on the fly.However it cannot be denied that the toxic effects of nano titanium dioxide,may be the titanium dioxide concentration that we used is too low,making its toxicity did not show its effect.Another possibility could be the time is too short and thus the impact on the host role has not arisen.Therefore we can only say that titanium dioxide nanoparticles in low concentration and shortened time won't affect intestinal bacteria and host.As for increasing the volume of titanium dioxide nanoparticles and long-term accumulation effect remains to be further researched.