Can the surface modification and/or morphology affect the ecotoxicity of zinc oxide nanomaterials?

Among nanomaterials, zinc oxide (ZnO) is notable for its excellent biocidal properties. In particular, it can be incorporated in mortars to prevent biofouling. However, the morphology of these nanomaterials (NMs) and their impact on the action against biofouling are still unknown. This study aimed to assess how the morphology and surface modification can affect the ecotoxicology of ZnO NMs. The morphologies evaluated were nanoparticles (NPs) and nanorods (NRs), and the ZnO NMs were tested pure and with surface modification through amine functionalization (@AF). The toxic effects of these NMs were evaluated by acute and chronic ecotoxicity tests with the well-established model microcrustacean Daphnia magna. The ZnO NMs were characterized by transmission electron microscopy, X-ray diffraction and infrared spectroscopy. The EC5048h to D. magna indicated higher acute toxicity of ZnO@AF NRs compared to all tested NMs. Regarding the chronic test with D. magna, high toxic effects on reproduction and longevity were observed with ZnO@AF NRs and effects on growth were observed with ZnO NRs. In general, all tested ZnO NMs presented high toxicity when compared to the positive control, and the NRs presented higher toxicity than NPs in all tested parameters, regardless of the form tested (pure or with surface modification). Additionally, the pathways of ecotoxicity of the tested ZnO NMs was found to be related to combined factors of Zn ion release, effective diameter of particles and NM internalization in the organism.

Investigation of toxicological effects of amorphous silica nanostructures with amine-functionalized surfaces on Vero cells.

Amorphous silica (SiO2) nanostructures are described in the literature as having low toxicity and are widely used in many industrial products. However, surface modifications, such as amine-functionalization, can result in increased cytotoxicity. In this study, amorphous SiO2 nanostructures (SiO2 NS) were synthesized and amine-functionalized with two different amine molecules: primary (SiO2 NS@1) and tri-amine (SiO2 NS@3). The materials were characterized by transmission electron microscopy (TEM), zeta potential (ZP), effective diameter (ED) and surface area measurements, X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The toxicity of the three SiO2 NS samples toward Vero cells was evaluated. According to the methyl thiazolyl tetrazolium (MTT) assay, the IC50,24h was 1.477 ±â€¯0.12 g L-1 for SiO2 NS, 0.254 ±â€¯0.07 g L-1 for SiO2 NS@1 and 0.117 ±â€¯0.05 g L-1 for SiO2 NS@3. The order of cytotoxicity was SiO2 NS@3 > SiO2 NS@1 ¼ SiO2 NS. There was an increase in malondialdehyde (MDA) levels and ROS productions in the cells exposed to all three materials. Also, TEM images showed damage on the mitochondria and rough endoplasmic reticulum.

Comparative assessment of toxicity of ZnO and amine-functionalized ZnO nanorods toward Daphnia magna in acute and chronic multigenerational tests.

Zinc oxide nanomaterials (ZnO NM) have been used in a large number of applications due to their interesting physicochemical properties. However, the increasing use of ZnO NM has led to concerns regarding their environmental impacts. In this study, the acute and chronic toxicity of ZnO nanorods (NR) bare (ZnONR) and amine-functionalized (ZnONR@AF) toward the freshwater microcrustacean Daphnia magna was evaluated. The ZnO NR were characterized by transmission electron microscopy (TEM), X-Ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and the zeta potential and hydrodynamic diameter (HD). The acute EC50(48h) values for D. magna revealed that the ZnONR@AF were more toxic than the ZnONR. The generation of reactive oxygen species (ROS) was observed in both NM. Regarding the chronic toxicity, the ZnONR@AF were again found to be more toxic than the ZnONR toward D. magna. An effect on longevity was observed for ZnONR, while ZnONR@AF affected the reproduction, growth and longevity. In the multigenerational recovery test, we observed that maternal exposure can affect the offspring even when these organisms are not directly exposed to the ZnO NR.