Silver nanoparticles (AgNPs) are widely used in numerous industries and areas of daily life, mainly as antimicrobial agents. The particles size is very important, but still not suffi ciently recognized parameter infl uencing the toxicity of nanosilver. The aim of this study was to investigate the cytotoxic effects of AgNPs with different particle size (~ 10, 40 and 100 nm). The study was conducted on both reproductive and pulmonary cells (CHO-9, 15P-1 and RAW264.7). We tested the effects of AgNPs on cell viability, cell membrane integrity, mitochondrial metabolic activity, lipid peroxidation, total oxidative and antioxidative status of cells and oxidative DNA damage. All kinds of AgNPs showed strong cytotoxic activity at low concentrations (2÷13 μg/ml), and caused an overproduction of reactive oxygen species (ROS) at concentrations lower than cytotoxic ones. The ROS being formed in the cells induced oxidative damage of DNA in alkaline comet assay. The most toxic was AgNPs<10 nm. The results indicate that the silver nanoparticles, especially less than 10 nm, may be harmful to the organisms. Therefore, risk should be considered when using nanosilver preparations and provide appropriate protective measures when they are applied.

In August 2016, tomato plants grown during a hot, wet summer with heavy soil flooding, displaying symptoms of wilting, dead plant, root rot with crown and stem rot, at Beni Suef and Fayoum governorates were examined. A number of 16 fungal isolates were isolated from tomato plants displaying the above symptoms. These isolates were classified as belonging to six species, namely: Alternaria solani, Chaetomium globosum, Fusarium solani, Fusarium oxysporum, Pythium spp. and Rhizoctonia solani. Isolates of Pythium spp. were prevalent and were found to be more pathogenic than the other fungal isolates. This species causes damping-off, root rot, sudden death, stem rot and fruit rot. The pathogen was identified as Pythium aphanidermatum based on morphological, cultural, and molecular characteristics. Biogenic silver nanoparticles (AgNPs) were produced using the F. oxysporum strain and characterized by transmission electron microscopy (TEM). The size of these spherical particles ranged from 10 to 30 nm. In vitro, biogenic AgNPs showed antifungal activity against P. aphanidermatum. In greenhouse and field experiments, AgNPs treatment significantly reduced the incidence of dead tomato plants due to root rot caused by P. aphanidermatum compared to the control. All of the investigated treatments were effective and the treatment of root dipping plus soil drenching was the most effective. To the best of our knowledge, this study describes P. aphanidermatum on tomato in Egypt for the first time. Also, biogenic AgNPs could be used for controlling root rot disease caused by this pathogen.

Prolonged exposure to UV radiation, and ever-increasing life expectancy, mean that an increasing proportion of the population suffers from clouding of the intraocular lens. Nowadays, the performance of intraocular implantation procedures is commonplace. Unfortunately, with the increasing number of operations, the number of postoperative complications is also increasing. One way to avoid complications may be to use an intraocular implant that has been immersed in a solution containing silver nanoparticles. As part of the study, four selected intraocular implants – that are available on the ophthalmic market – were tested. In order to investigate the effect of silver particles on the optical properties of the implants, tests were carried out using a UV-VIS spectrophotometer. Two series of implants were tested: before and after immersion in a silver solution. The implants were immersed for a period of 7 days. It was found that the presence of silver particles does not have a negative impact on the translucency of the implants.

In this study, Ag-impregnated silica aerogel composites were fabricated via wet impregnation. In this approach, silver salt was reduced with ethylene glycol in the presence of polyvinylpyrrolidone (PVP) at reaction temperature 80°C. PVP was used as a capping agent to protect the Ag nanoparticles (NPs) from agglomeration. Wet impregnation was used to synthesize the Ag/SiO2 composite by combining the reduction of AgNO3 with a silica aerogel slurry. Experimental results showed that the AgNO3 concentration and PVP: AgNO3 ratio had an active influence on the growth of Ag NPs on silica surfaces. The X-ray diffraction (XRD) patterns of the composite material showed no imprints of impurities or parasitic materials except for Ag and SiO2. Scanning electron microscopy (SEM) images revealed that the Ag NPs were well impregnated into the porous silica aerogel structure. It was found that SiO2 aerogel surfaces were homogeneously surrounded by the Ag NPs.

Since silver nanoparticles (AgNPs) are used as nanofungicides and nanopesticides in agriculture, the toxicity of AgNPs as well as AgNO3 must be determined. Besides this, we evaluated the combined effects of salicylic acid (SA) and nitric oxide (NO) on responses of Phlomis tuberosa plants to Ag-induced stress. The results of growth parameters together with measurement of malondialdehyde (MDA) indicated that exposure to 1000 mg L–1 of AgNPs or AgNO3 exerted more toxicity, which was closely associated with the over– accumulation of ROS and the reduction of photochemical functioning. However, SNP (NO) and SA addition successfully alleviated adverse impact of AgNPs on Phlomis seedlings. Maximum amelioration of Ag-induced stress was found by combined treatments of SA+NO. Phlomis plants primed with SA+NO exhibited higher synthesis of chlorophyll b and carotenoid pigments to ameliorate AgNP-induced adverse effects on chlorophyll fluorescence parameters. SA+NO led to high levels of proline under both AgNPs and AgNO3 treatments. A further increase in antioxidants (phenolic compounds) was observed in NO-primed plants under AgNPs- induced stress, which was attendant with the high level of CAT and APX activities. Increase in total Ag translocation into shoot organs and cell survival were also enhanced by SA+NO under AgNPs stress. We concluded that SA+NO mitigated the inhibitory effects of AgNPs stress on the photosynthetic apparatus by increasing the phenolic compounds and carotenoids as well as by regulating accumulation of Ag, ROS and antioxidants. The present findings provide important knowledge to design strategies that minimize the negative impact of AgNPs and AgNO3 on crops.