Magnesium oxide nanoparticles alleviate arsenic toxicity, reduce oxidative stress and arsenic accumulation in rice (Oryza sativa L.).

Magnesium oxide nanoparticles (MgO NPs) have been attracted by the scientific community for their combating action against heavy metal stress in plants. However, their role towards the mitigation of arsenic (As) induced toxicity is still obscure. In the present study, MgO NPs were synthesized through the green route and assessed their efficacy towards the reduction of As accumulation and phytotoxicity in As-stressed rice cultivar MTU-1010 under laboratory conditions. Initially, rice seedlings were grown under separate and combined applications of As (10 mg/L) and MgO NPs (0, 10, 50, and 100 mg/L) and further analyzed plant growth attributes and As accumulation in rice seedlings. Characterization of biosynthesized MgO NPs by UV-Vis spectrophotometer, transmission electron microscopy (TEM), scanning electron microscopy with energy-dispersive X-ray analysis (SEM-EDX), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) analysis showed the cubic in shape, and crystalline nature (73.10%) with average size ranges from 17-23 nm. The growth experiment showed a significant (p < 0.05) increase in seed germination, seedling growth, photosynthetic and other pigments content, and biomass accumulation in rice seedlings under the combined application of As (10 mg/L) and MgO NPs (50 mg/L) as compared to only As (10 mg/L) treatment. Additionally, As exposure resulted in declined primary metabolites such as soluble sugars and protein. However, the application of MgO NPs exhibited the alleviation of As toxicity through significant (p < 0.05) reduction of As accumulation by 34 and 53% in roots and 44 and 62% in shoots of rice seedlings under 50 and 100 mg/L MgO NPs supplementations, respectively and restored the accumulation of the primary metabolites. Furthermore, MgO NPs demonstrated the ability to scavenge reactive oxygen species (ROS) like hydrogen peroxide (H2O2) and superoxide anion (O2•-), through significant (p < 0.05) promotion of non-enzymatic (carotenoid, anthocyanin, flavonoid, and proline) and enzymatic (CAT, POD, and SOD) antioxidant defence under As stress. These findings highlighted the potential of green synthesized MgO NPs towards the mitigation of As contamination in rice plants. However, future study is necessary to unfold the actual mechanisms responsible for the protective effects of MgO NPs and to screen out the optimal dose to be used to formulate a potent nanofertilizer for sustainable rice production in metal-contaminated soils.

Bio-fabricated silver nanoparticles for controlling dengue and filaria vectors and their characterization, as well as toxicological risk assessment in aquatic mesocosms.

The present study is focused on synthesis of silver nanoparticles from weeds and an assessment of their mosquito larvicidal efficacy. This study also presented the toxicological effects as well as the stability of these nanoparticles in aquatic mesocosms. The weed Digiteria sanguinallis was first time used for the synthesis of silver nanoparticles. The synthesized nanoparticles were characterized by various analytical techniques, such as UV-VIS, TEM, FESEM, EDX, XRD, FTIR, and zeta potential study. The result revealed that the nanoparticles are crystalline, spherical shape with band gap 2.44 eV, and average size 18 nm. The LC50 value of synthesized AgNPs were recorded as 7.47 and 6.31 mg/L at 24 h against Cx. quinquefasciatus and A. albopictus respectively. In contrast, larvicidal activity of weed extract was insignificant against two target species. In aquatic mesocosm study, AgNPs (LC50 dose) does not alter the nature of water parameters within experimental period. However only EC % and ORP were changes because of silver ion oxidation. In biochemical parameters, only stress enzymes for animal and plant species were moderately altered under long term exposure. But glycogen, protein, and AchE of two mosquito species were significantly changed under same mesocosm setup within short exposure. Comparatively, in control mesocosm, synthesized AgNPs are naturally change their nano form within 20 days with the presence of all non-target species and pond sediment. Therefore, it can be concluded that biosynthesized AgNPs could be used as a larvicidal agent in near future with negligible effects on aquatic organisms.

Genotoxicity study of nano Al2O3, TiO2 and ZnO along with UV-B exposure: An Allium cepa root tip assay.

The present effort aims to investigate the cytotoxic and genotoxic impact of three widely used nanoparticles (ZnO, TiO2 and Al2O3) on root cells of Allium cepa as a test organism. The root tip of Allium cepa were treated with three different concentrations (0.1 10 and 100 mg/L) of the above-mentioned NPs and the observations were recorded after proper growth of root under both nanoparticle solutions and UV-B exposure in combined conditions and separately. The parameters such as mitotic index, various forms of chromosomal aberrations, various reactive oxygen species (ROS) generation such as superoxide radical (O-2·), hydrogen peroxide, hydroxyl radical (·OH), lipid peroxidation and bio-uptake of nanoparticles were assessed. The results revealed that for all the three nanoparticles, mitotic index (MI) was highly reduced in comparison to control. Among the three nanoparticles, the MI value of TiO2 was 59.5% at 0.1 mg/L. Chromosomal aberration data suggest that nano Al2O3 exhibited disturbed metaphase at 0.1 mg/L, and abnormal anaphase and sticky metaphase at 10 and 100 mg/L, respectively. Similarly, lagged metaphase and anaphase with multiple chromatin bridges were recorded for both nano ZnO and nano TiO2 at 0.1 mg/L. But, nonsignificant (p > 0.05) results were recorded between only nano metal oxide and UV-B along with nano metal oxide. ROS generation data revealed that ZnO is more active under UV-B than TiO2 and Al2O3. The cellular deformation and the existence of metal in A. cepa under nano ZnO, TiO2 and Al2O3 treatment were evaluated by Scanning Electron Micrograph (SEM) and X-ray fluorescence (XRF) study, respectively. It may safely be concluded that with respect to chromosomal aberration and mitotic index, out of the three nanoparticles, Al2O3 is the most severe at higher concentrations and nano ZnO shows lowest mitotic index under UV-B exposure.