Toxicity Of ZnO Nanoparticles On Human Hepatocyte And Embryonic Kidney Cells

ZnO nanoparticles (ZnO NPs) have strong photocatalysis as well asresistance of oxidantion, corrosion and ultraviolet compare with micro-ZnO, andhas been widely used in consumer and industrial products, especially photovoltaics,rubber industry, food additives, bio-medical etc. ZnO NPs can take place into theorganism through the skin, respiratory or digestive, saving in the body, but it’sdifficult to discharge such small material. The potential toxic effects of ZnO NPs,which caused the people’s attention for its security, had become a research hotpot.For toxicity evaluations, human hepatocyte cells HL-7702and embryonic kidneycells HEK293cellular morphology exposed to ZnO nanoparticles, mitochondrialfunction (MTT assay), Oxidative stress markers (GSH, MDA and SOD), DNAdamage (SCGE assay), chromosomes damage(Micronucleus test), protein oxidativedamage(DNPH assay) and apoptosis detection (DNA-laddering) were assessed undercontrol and exposed conditions (24h of exposure).1. In Vitro Cytotoxicity of ZnO Nanoparticles in HL-7702and HEK293cellsThe aim of the study is to determine the optimal viability assay for use with ZnONPs in order to assess their toxicity. We confirmed the size of particles by TEM. Fortoxicity evaluations, cellular morphology and mitochondrial function (MTT assay)were assessed under control and exposed conditions.The results showed that cell viability significantly decreased in HL-7702cellsexposed to ZnO NPs (≥25μg/mL), while HEK293cells tested displayed cell viabilityat higher doses (10μg/mL), and a dose-response relationship was observed. Themicroscopic studies demonstrated that nanoparticle-exposed cells at higher dosesbecame abnormal in size, displaying cellular shrinkage, and an acquisition of anirregular shape.2. DNA Damage of HL-7702and HEK293cells by ZnO nanoparticlesTo study the genetoxic effect of ZnO nanoparticles with different concentrations onhuman cells (HL-7702and HEK293), they were exposed to ZnO nanoparticles at theconcentration of10,25,50,75and100μg/mL for12h,24h and48h. The modified comet assay and micronucleus test were performed to research the effect of DNAdamage and chromosomal damage. The results showed that the DNA damage oftreated groups was more serious. The tail moment, olive tail moment and tail DNApercentage were significantly increased with the rising of ZnO nanoparticlesconcentration, but the head DNA percentage was decreased. Micronucleus assayshowed that the micronuclear rates increased. The result showed that ZnO NPs hadthe genotoxicity effect on cells in vitro, leading to DNA damage and chromosomaldamage.3. Oxidative Stress on HL-7702and HEK293cells in the Presence of ZnOnanoparticlesIn order to verify whether ZnO nanoparticles could induce oxidative damage,oxidative stress markers (MDA, GSH and SOD) were assessed under control andexposed conditions (10,25,50,75and100μg/mL for24h exposured), proteincarbonyl contents using DNPH assay to study the protein damage. The resultsexhibited significant depletion of GSH and SOD level, increase in MDA levels in adose range from10μg/mL to100μg/mL, and the contents of protein carbonyl wascreased in the high dosage groups(P＜0.05), which suggested that cytotoxicity ofZnO NPs in liver and kidney cells might be mediated through oxidative stress, and adose-response relationship was observed. Though the exact mechanism behind ZnONPs toxicity is suggested oxidative stress playing an important role in ZnO NPselicited cell membrane disruption, DNA damage and subsequent cell death.4. Apoptosis of HL-7702and HEK293cells by ZnO nanoparticlesTo evaluate the effect of ZnO nanoparticles on the apoptosis of HL-7702andHEK293cell lines, cell apoptosis were determined by DNA-laddering assay. Theelectrophoresis results showed DNA fragmentation in100-200bp, which indicate thatin vitro ZnO nanoparticles can significantly induce apoptosis in human hepatocyteand embryonic kidney cells, this may be one of the mechanisms of cytotoxicity butneeds further studies.