| Nanomaterials have many new physical and chemical properties, as well as many new biological characteristics, which are due to their extremely small size and special structures. So they can be applicated in various fields, such as medicine, manufacture, and daily necessities, communicational engineering and environmental engineering, and so on. Therefore, nanoscience and nanotechnology were listed as the top priority of the science and technological development strategies in many countries. With the changes in physical and chemical properties, nanomaterials may have some new biological effects, especially the potential with some new effects which are not known by us. This brings an important scientific issue, that is, whether the current safety assessment methods are applicable for assessing the safety of nanomaterials. With the rapid development of nanotechnology, the safety evaluation of nanomaterial and nano products has become the urgent need to be solved. It has become one of the bottlenecks in the development of nanotechnology as well as the forefront of research and hot issue of toxicology.Genotoxicity assessment is an important part of safety evaluation, which has been researched a lot at home and abroad. However, these researches focus mainly on finding whether the nanomaterials have genotoxicity and on the relationship of physical properties and genotoxicity. but less involved in research that whether the current methods of genotoxicity assessment are suitable for nanomaterial. So the objective of our research is to reveal the genotoxic characteristics of nanomaterials more thoroughly.According to the different compositions and structures of nanomaterials, they can be divided into four types, they are, metal class, dendrimers, complexes and carbon class. Therefore, we chose some representative materials from four kinds of nanomaterials to research and study their genotoxicity by using single cell in the same exposure condition. The outcome measures include DNA damage, gene mutations and chromosome aberration, and so on. At the same time, we also study the same substances of micrometer scale as control materials. Thus, the results of our study may reveal the genotoxic characteristics of nanomaterials systematically and provide a scientific basis for the determination of method of assessment nanomaterial genotoxicity.Objective:To reveal the genotoxic characteristics and the possible genotoxic mechanisms of nanomaterials, and to provide the basis for the decision-making and choice of strategies about the safety evaluation of nanomaterials by comparative study of microscale and nanoscale materials.Methods:The L5178Y cell lines were selected as tested cells, and the cytokinesis-block micronucleus cytome assays and the alkaline comet assays were chosen to study the characteristics of chromosome breakage, chromosome loss, chromosome rearrangements, gene amplification and DNA damage caused by the microscale and nanoscale materials. The experimental data were expressed as mean and standard deviation (X±S) and analyzed by factorial two-way ANOVA. Multiple comparisons between groups and doses was done by LSD method using SPSS13.0.Results:1. Compared with negative control group, significant increases were observed in the numbers of type I micronucleus and nuclear buds in nano-ZnO group at the dosage of0.5μg/ml (P=0.003. P=0.027), Nucleoplasmic bridges (NPBs) and type II micronucleus were induced by nano-ZnO at the dosage of2.5μg/ml (P=0.001, P=0.012). Micro-ZnO particles basically had no effect on these effects (P=0.694, P=0.058, P=0.074, P=0.438). Compared with micro-ZnO group, significant differences were observed in the numbers of type Ⅰ micronucleus, type Ⅱ micronucleus and nuclear buds in nano-ZnO group (P=0.007, P=0.045, P=0.012). It was showed by alkaline comet assay that DNA damages were induced by nano-ZnO at the dosage of0.5μg/ml or by micro-ZnO at2.5μg/ml. Compared with micro-ZnO group, significant differences were observed in the Tail DNA%, Tail Length and Olive Tail Moment (OTM) in nano-ZnO group (P=0.015, P=0.008, P=0.001).2. Compared with control group, significant increases were observed in the numbers of type I micronucleus in nano-TiO2group at the dosage of1.56μg/ml (P=0.005), nuclear buds and NPBs at3.13μg/ml (P=0.015, P=0.031), and type Ⅱ micronucleus effect at6.25μg/ml (P<0.001). However, micro-TiO2can also increase the number of type I micronucleus at the dosage of6.25μg/ml (P=0.001) and the number of NPBs at12.5μg/ml (P=0.015). But the numbers of type II micronucleus and nuclear buds were not increased in micro-TiO2group (P=0.068, P=0.076). Compared with micro-TiO2group, significant differences were observed in the number of type I micronucleus, type II micronucleus and nuclear buds in nano-TiO2group (P=0.005, P=0.010, P=0.031). It was showed by alkaline comet assay that compared with control group, significant differences were observed in the Tail Length and OTM in nano-TiO2group at0.78μg/ml dose (P=0.001, P=0.029) and in the Tail Length in micro-TiO2group at3.13μg/ml. Compared with micro-TiO2group, significant differences were observed in the Tail DNA%, Tail Length and OTM in nano-TiO2group (P=0.003, P<0.001, P<0.001).3. Compared with control group, significant increases were observed in the numbers of type I micronucleus and NPBs in nano-polystyrene group at the dosage of40μg/ml (P=0.026, P=0.023) as well as in micro-polystyrene group at80μg/ml (P=0.026, P=0.023), The increasement of type II micronucleus were observed in nano-polystyrene group at80μg/ml (P=0.008) and in micro-polystyrene group at160μg/ml (P=0.008). Nano-polystyrene could induce the increasement of nuclear buds at the dosage of160μg/ml (P=0.030) but micro-polystyrene had no effect at the same dose (P=0.093). It was showed by alkaline comet assay that compared with control group, significant differences were observed in Tail DNA%, Tail Length and OTM in nano-polystyrene group at20μg/ml dose (P=0.030, P=0.010, P=0.001), but did not observed in micro-polystyrene group (P=0.653, P=0.089, P=0.082).4. Compared with control group, significant increases were observed in the numbers of type I micronucleus, type II micronucleus and nuclear buds in CdTe/Cds/ZnS630group at the dosage of2.5μg/ml (P<0.001, P<0.001, P=0.010) and NPBs at the dosage of5.0μg/ml (P=0.001). CdTe/Cds/ZnS570could induce type I micronucleus and nuclear buds at0.63μg/ml (P=0.042, P=0.001) and type Ⅱ micronucleus and NPBs at1.25μg/ml These kinds of damages induced by CdTe/Cds/ZnS570were greater than by CdTe/Cds/ZnS630at1.25μg/ml or above (P=0.001, P<0.001, P=0.035, P=0.001). It was showed by alkaline comet assay that compared with control group, significant differences were observed in Tail Length in CdTe/Cds/ZnS630group at0.63μg/ml dose (P=0.007) and in Tail DNA%, Tail Length and OTM in CdTe/Cds/ZnS570(P<0.001, P=0.002, P=0.002).5. Compared with control group, significant increases were observed in the number of type I micronucleus in singlewalled carbon nanotube (SWCNT) group at the dosage of40μg/ml (P<0.001). Type II micronucleus and nuclear buds were induced by SWCNT at the dosage of80μg/ml (P=0.010, P=0.013), so did in NPBs at160μg/ml (P=0.008). Morewalled carbon nanotube (MWCNT) led an increase in the numbers of type Ⅰ micronucleus and nuclear buds at20μg/ml (P=0.003, P=0.038), type Ⅱ micronucleus at40μg/ml (P=0.024) and NPBs at80μg/ml (P=0.006). However, carbon black particles did not significantly induce the increasement of type Ⅰ micronucleus, type Ⅱ micronucleus, NPBs or nuclear buds (P=0.088, P=0.526, P=0.104,P=0.051).Conclusions:1. The properties and strength of genotoxicity were significantly different between nano-ZnO/nano-TiO2(belong to metal class nanomaterials) and their micro-scale materials. Nano-ZnO and nano-TiO2can induce the generation of type I micronucleus, type II micronucleus, nuclear buds and NPBs and the damage of DNA, whereas only DNA damage is caused by micro-ZnO and type I micronucleus and NPBs can be induced by mico-TiO2.2. The genotoxicity of nano-polystyrene (belong to dendrimers nanomaterials) is stronger than those of micro-polystyrene. Nano-polystyrene can induce the generation of type I micronucleus, type II micronucleus, nuclear buds, NPBs and DNA damage, whereas nuclear buds are not caused by micro-polystyrene even at higher levels, which indicated that there are differences in the genotoxic properties between nano-polystyrene and micro-polystyrene.3. CdTe/Cds/ZnS630and CdTe/Cds/ZnS570(belong to complexes nanomatcrials) can induce the generation of type Ⅰ micronucleus, type Ⅱ micronucleus, nuclear buds, NPBs and DNA damage, but the genotoxicity of CdTe/Cds/ZnS570is stronger than that of CdTe/Cds/ZnS630.4. The properties of genotoxicity are different between CNTs (SWCNT and MWCNT, belong to carbon class nanomaterials) and micro-carbon black particles. CNTs can induce the generation of type Ⅰ micronucleus, type Ⅱ micronucleus, nuclear buds and NPBs, but micro-carbon black particles can not. However, the genotoxicity of MWCNT is stronger than that of SWCNT. |
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