Toxic Effects Of Two Same Particle Size Nanoscale Oxides Stress On Three Species Of Green Algae

Deemed as a new material, nanomaterials is an important foundation for the development of nanotechnology, and is a significant material foundation for in-depth development of a variety of disciplines such as future information technology and biotechnology. Up to till now, people have achieved a series of influential creative results in the field of nanotechnology. Meanwhile, the biological safety of our lives, affected by nanomaterials, also attracted people’s attention when we frequently use it and also gain from it. As a new type of semiconductor nanomaterials, the characteristics of its toxicology research is determined by the unique physical and chemical properties of nanoparticles NiO (nNiO) and nano-silica (nSiO2), which can enter the soil, air and water environment through multiple routes, and finally into the human body. Therefore, the safety evaluation and risk assessment of nNiO and nSiO2has become a new toxicology topic of the21st century. The toxic effects of two nano-oxides—nNiO and nSiO2, which have the same particle size (30nm), stress on three tested green algae(Scenedesmus quadricauda, Chlorella vulgaris and Selenastrum capricornutum) was investigated, which lasted for10days. It focused on the aspects of the morphology, growth conditions and physiological and biochemical indexes, to assess the safety of nNiO and nSiO2stress on aquatic plants, and to provide theoretical basis for mechanism of nanometer materials inhibiting algae’s growth.The experiment researched on the toxic effects of the two same particle size nano-oxides (nNiO and nSiO2) suspension to the three green algae. The microscopic observation; cell density and IR, contents of chlorophyll a, chlorophyll b, total chlorophyll, carotenoid contents from Od to10d(total11days) were measured in different concentrations of two nano-oxides suspensions of0,60,120,180,240,300mg/L; the protein concentrations, contents of malonyldialdehyde (MDA), the activities of superoxide dismutase (SOD) and catalase (CAT) from the first day of every other day(total5days) were also measured under the two nano-oxides suspensions concentrations. The results indicated three points:(1) the toxic effects of the two nano-oxides with the same particle size (30nm) acted on the three species of algae is nNiO> nSiO2; morphological, under this stress, all the three species of algae would agglomerate and algal cells would also lose of green, deform, swell and apoptosis.(2) The growth of three species were inhibited under the stress of nNiO, that Scenedesmus quadricauda and Selenastrum capricornutum (the second day of300mg/L treatment group) had achieved and maintained the maximum inhibition rate (IR>50%), Chlorella vulgaris (the fourth day of300mg/L treatment group) also had the same result, effects of lower concentrations of nNiO (60-120mg/L) on tested algae (Chlorella vulgaris and Selenastrum capricornutum, in addion to Scenedesmus quadricauda) showed "inhibition-promotion-inhibition", which promoted the growth of these two algae, that showed obvious dose effect during the same time, while higher concentrations (180-300mg/L) showed inhibited cell growth; affects the performances of the three algae physiological indicators were as follows:the chloroplast pigment and protein content decreased, MDA content increased and the antioxidant vitality reduced.(3) The growth of three species were inhibited under the stress of nSiO2, but were not serious and able to grow, both had the "low concentration to promote growth and high concentrations inhibit the growth". And the dose-effect of different concentration of nSiO2stress was obviously in the same time period, and the IR of three species of algae did not exceed50%in the entire processing cycles (10d); affect the performances of the three algae physiological indicators:affect the performances of the three algae physiological indicators:the chloroplast pigment and protein content increased, MDA content of Chlorella vulgaris was increased, MDA content of the other two algae were decreased, and antioxidant activity was gradually increased. These results confirmed that, the exposure of nNiO and nSiO2did have toxic effects to the three tested green algae, and showed a dose effect.