Silver ions increase plasma membrane permeability through modulation of intracellular calcium levels in tobacco BY-2 cells

Synthetic auxin herbicide 2,4-D and its influence on a model BY-2 suspension

2,4-D is a broadly used auxin herbicide. The presence of the 2,4-D synthetic auxin in the medium is imperative for long-term BY-2 tobacco suspension viability. The precise mechanism of this symbiosis of the suspension and the synthetic auxin remains unclear. Our goal was to study the hormonal regulation of the growth of the cell suspension; and to describe the experiments clarifying the interaction between the chosen growth regulators and phytohormones on the cellular level, specifically between the 2,4-D synthetic auxin and the native stress phytohormone - ethylene. This study examined the influence of low 2,4-D concentrations stimulating cell growth in vitro as well as the influence of high herbicide concentrations on the model tobacco BY-2 suspension. The culture took 6 days. Different parameters were evaluated, including the influence of different 2,4-D concentrations on the production of the phytohormone ethylene and its precursor 1-Aminocyclopropane-1-carboxylic acid (ACC) in the tobacco cells. The content of 2,4-D in the cells and the medium was established. The observations of the morphological changes showed that a heavy impregnation of the cell walls taking place depending on the concentration of 2,4-D. A dramatic increase in protective polysaccharides and a remodulation of the cell walls by the formation of a pectin shield in artificial conditions were expected and observed. At the same time, massive production of the stress phytohormone ethylene took place, and, because of that, plant mutagenicity, anomalous tumour-type proliferation growth, and the production of supercells were observed. The hypothesis of the protective shield is discussed.

Impact of magnetic field on the translocation of iron oxide nanoparticles (Fe3O4) in barley seedlings (Hordeum vulgare L.)

The effect and contribution of an external magnetic field (MF) on the uptake and translocation of nanoparticles (NPs) in plants have been investigated in this study. Barley was treated with iron oxide NPs (Fe3O4, 500 mg/L, 50-100 nm) and grown under various MF strengths (20, 42, 125, and 250 mT). The root-to-shoot translocation of NPs was assessed using a vibrating sample magnetometer (VSM) and inductively coupled plasma optical emission spectrometry (ICP-OES). Additionally, plant phenological parameters, such as germination, protein and chlorophyll content, and photosynthetic and nutritional status, were examined. The results demonstrated that the external MF significantly enhances the uptake of NPs through the roots. The uptake was higher at lower MF strengths (20 and 42 mT) than at higher MF strengths (125 and 250 mT). The root and shoot iron (Fe) contents were approximately 2.5-3-fold higher in the 250 mT application compared to the control. Furthermore, the MF treatments significantly increased micro-elements such as Mn, Zn, Cu, Mo, and B (P < 0.005). This effect could be attributed to the disruption of cell membranes at the root tip cells caused by both the MF and NPs. Moreover, the MF treatments improved germination rates by 28%, total protein content, and photosynthetic parameters. These findings show that magnetic field application helps the effective transport of magnetic NPs, which could be essential for NPs-mediated drug delivery, plant nutrition, and genetic transformation applications.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-023-03727-4.

Phytotoxic Action of Silver Nanoparticles on Lemna minor: Multi-Parameter Analysis of Different Physiological Processes

Considering the widespread use of silver nanoparticles (AgNPs) and their consequent build-up in waterways, there is a concern about the hazardous effect of AgNPs for aquatic ecosystems. The aim of this study was to clarify the mechanism of the action of AgNPs on duckweed (Lemna minor L.) by evaluating multiple parameters in different physiological processes. Duckweed was treated with AgNPs in a concentration range of 0.5 to 5 mg/L over a 7-day period. The analysis revealed that the AgNP-treated duckweed accumulated Ag in accordance with increasing AgNP concentrations. Furthermore, higher concentrations (2 and 5 mg/L) of AgNPs negatively affected N, P and especially K and Mg levels in the plant tissue. Accordingly, the plant growth and photosynthetic parameters were more inhibited in response to higher concentrations of AgNPs. Nanosilver significantly increased the generation of ROS at higher concentrations, although lipid peroxidation was significant even at the lowest concentration of AgNPs. However, defense mechanisms were able to counteract AgNP-induced oxidative stress and balance the intracellular redox status, as evidenced by increased activities of the main detoxification enzymes. With this experimental setting, AgNPs exhibited a relatively weak phytotoxicity at 0.5 and 1 mg/L; nevertheless, silver in a nano form poses a hazard for plants, considering its continuous release into aquatic environments.

Green synthesis, characterization and biological activity of Solanum trilobatum-mediated silver nanoparticles

Biologically inspired synthesis of nanoparticles was found to be more attractive in metal nanoparticle synthesis. The present study reported an in-situ biogenic synthesis of silver nanoparticles (AgNPs) using Solanum trilobatum aqueous leaf extract. On this basis, the aqueous leaf extract of S. trilobatum acted as a reducing agent and stabilizing agent to synthesize highly stable AgNPs at ambient temperature. Eventually, the synthesized and stabilized AgNPs surface plasmon resonance was near 430 nm through a UV–visible (UV–vis) spectrophotometer. Here, the stability of the silver colloids monitored through zeta potential and mean particle size was evaluated through diffraction light scattering (DLF). Further, the average particle size was found to be 27.6 nm and spherical, confirmed with transmission electron microscopy (TEM). Also, colloidal AgNPs and aqueous extract are found to be rich sources of antioxidants and exhibit higher free radical scavenging ability. Thus, efficient inhibition with COX1 and COX2 enzymes and the protective effect with human red blood cell (HRBC) membrane stability showed significant results. These features are promising, suggesting the possibility of the AgNPs to be useful to disease-modifying for treating inflammatory disorders and associated complications.

In Vitro Root Induction from Argan (Argania spinosa (L.) Skeels) Adventitious Shoots: Influence of Ammonium Nitrate, Auxins, Silver Nitrate and Putrescine, and Evaluation of Plantlet Acclimatization

Argania spinosa (L.) Skeels is an endangered plant species endemic to Morocco. In recent years, attempts to develop in vitro regeneration systems for this species were made. However, rooting and acclimatization of in vitro plants have been a bottleneck for successful propagation. In the present study, the effects of different concentrations of auxins, putrescine, silver nitrate (AgNO₃) and ammonium nitrate on the in vitro rooting of adventitious shoots of two argan genotypes "Mejji" and "R'zwa", were evaluated. The highest rooting percentages (86.6% in "Mejji" and 84.4% in "R'zwa") were observed on Murashige and Skoog (MS) medium modified by reducing the ammonium nitrate concentration and supplemented with 1.5 mg L^-1 indole-3-butyric acid (IBA), 0.5 mg L^-1 1-naphthalene acetic acid (NAA), 2 mg L^-1 AgNO₃ and 160 mg L^-1 putrescine. This medium resulted in the development of a good root system after only 10 days of culture. Plantlet acclimatization was carried out using different substrate mixtures, and high survival rates (100%) were observed when the substrate contained either peat alone or a sand-peat mixture (1:1, w/w). The high percentages of rooting and acclimatization reported in the present study are of high importance for rapid and large-scale propagation of this endangered species.

Positive effects of metallic nanoparticles on plants: Overview of involved mechanisms

Engineered nanoparticles (NPs) are considered as potential agents for agriculture as fertilizers, growth enhancers and pesticides. Therefore, understanding the mechanisms that are responsible for their effects is important. Various studies demonstrated that the application of nontoxic concentrations can promote seed germination, enhance plant growth and increase the yield. Moreover, NPs can be used to protect plants from environmental impacts such as salt or drought stress and diminish accumulation and toxicity of heavy metals. NPs can serve as a source of micronutrients (e.g. ZnO, iron- and manganese-based NPs), thus increasing fitness and helps plants to cope with stress conditions. TiO₂ and iron-based NPs are able to delay senescence and speed-up cell division via changes in phytohormonal levels. The application of some NPs can promote the activity of enzymes such as amylase, nitrate reductase, phosphatase, phytase and carbonic anhydrases, which are involved in metabolism and nutrient acquisition. E.g. ZnO and TiO₂ NPs can stimulate chlorophyll biosynthesis and photosynthetic activity. Iron-based and CeO₂ NPs enhance stomata opening resulting in better gas exchange and CO₂ assimilation rate. NPs can also modulate oxidative stress by the stimulation of the antioxidant enzymes such peroxidases and superoxide dismutase. However, the knowledge about the fate, transformation, and accumulation of NPs in the environment and organisms is needed prior to their use in agriculture to avoid negative environmental impacts. Higher or lower toxicity of various NPs was established for microorganisms, plants or animals. In this overview, we focused on the possible mechanisms of Ag, ZnO, TiO₂, Fe-based, CeO₂, Al₂O₃, and manganese-based NPs responsible for their positive effects on plants.

Embryotoxicity of silver nanomaterials (Ag NM300k) in the soil invertebrate Enchytraeus crypticus - Functional assay detects Ca channels shutdown

Despite that silver (Ag) is among the most studied nanomaterials (NM) in environmental species and Ag's embryotoxicity is well known, there are no studies on Ag NMs embryotoxicity in soil invertebrates. Previous Full Life Cycle (FLC) studies in Enchytraeus crypticus, a standard soil invertebrate, showed that Ag materials decreased hatching success, which was confirmed to be a hatching delay effect for silver nitrate (AgNO₃) and mortality for Ag NM300K. In the present study, we aimed to investigate if the impact of Ag takes place during the embryonic development, using histology and immunohistochemistry. E. crypticus cocoons were exposed to a range of concentrations of Ag NM300K (0-10-20-60-115 mg Ag/kg) and AgNO₃ (0-20-45-60-96 mg Ag/kg) in LUFA 2.2 soil, in an embryotoxicity test, being sampled at days 1, 2, 3 and 6 (3, 4, 5 and 7 days after cocoon laying). Measured endpoints included the number of embryonic structures, expression of transferrin receptor (TfR) and L type calcium channels (LTCC) through histological and immunohistochemistry analysis, respectively. Results confirmed that Ag materials affected the embryonic development, specifically at the blastula stage (day 3). The expression and localization of TfR in E. crypticus was shown in the teloblasts cells, although this transcytosis mechanism was not activated. Ag affected calcium (Ca) metabolism during embryonic development: for AgNO_3, LTCC was initially activated, compensating the impact, for Ag NM300K, LTCC was not activated, hence no Ca balance, with irreversible consequences, i.e. terminated embryonic development. An Adverse Outcome Pathway was drafted, integrating the mechanisms here discovered with previous knowledge.

Role of inorganic nanoparticle degradation in cancer therapy

Nanomaterials are currently widely exploited for their potential in the development of novel cancer therapies, and so far, mainly nanoparticles (NPs) consisting of liposomes and polymers have made their way into the clinic. However, major bottlenecks for the clinical translation of other types of NPs (i.e. inorganic) are the lack of knowledge concerning their long-term distribution in vivo and their potential toxicity. To counter this, various research groups have worked on soluble NPs, such as zinc oxide (ZnO), copper oxide (CuO), and silver (Ag), which tend to dissolve spontaneously into their ionic form, releasing toxic metal ions and leading to reactive oxygen species (ROS) generation when exposed to cellular environments. By fine-tuning the dissolution kinetics of these NPs, it is possible to control the level of ROS production and thus cytotoxicity to selectively destroy tumor tissue. Specifically, cancer cells tend to exhibit a higher basal level of oxidative stress compared to normal cells due to their higher metabolic rates, and therefore, by engineering NPs that generate sufficient ROS that barely exceed toxic thresholds in cancer cells, normal cells will only experience reversible transient damage. This review focuses on the use of these soluble inorganic NPs for selective cancer therapy and on the various in vitro and in vivo studies that have aimed to control the dissolution kinetics of these NPs, either through particle doping or surface modifications.

Time of In Vitro Anther Culture May Moderate Action of Copper and Silver Ions that Affect the Relationship between DNA Methylation Change and the Yield of Barley Green Regenerants

Plant anther culture allows for the regeneration of uniform and homozygous double haploids. However, off-type regenerants may appear as a result of so-called tissue culture-induced variation (TCIV). In addition, the presence of Cu²⁺ and Ag⁺ ions in the culture medium might influence the number of green plants. The regenerants were obtained via anther cultures of barley under varying Cu²⁺ and Ag⁺ ion concentrations in the induction medium during distinct time conditions. DArTseqMet markers were evaluated based on regenerants and donor plants and delivering data on DNA demethylation (DM) and de novo methylation (DNM) and changes in methylation (Delta). The number of green regenerated plants per 100 anthers (GPs) was evaluated. The Cu²⁺ and Ag⁺ ion concentrations moderated relationships between Delta and the number of green plants conditional on time of tissue cultures. Depending on the ions, moderated moderation is valid within the different time of anther culture. When the highest concentration of copper is analyzed, plant regeneration is possible under short ‘Time’ (21 days) of anther culture wherein Delta is negative or under elongated Time when Delta is positive. Under 21 days of culture, the highest concentration of silver ions and when Delta is negative, some regenerants could be evaluated. However, under high Ag⁺ concentration when Time of culture is long and Delta positive, the highest number of green plants could be obtained.

Metabolic Changes Induced by Silver Ions in Carlina acaulis

Silver is one of the most toxic heavy metals for plants, inducing various toxic symptoms and metabolic changes. Here, the impact of Ag(I) on Carlina acaulis physiology and selected metabolites was studied using two Ag concentrations (1 or 10 µM) after 14 days of exposure. The higher concentration of Ag(I) evoked reduction of growth, while 1 µM Ag had a growth-promoting effect on root biomass. The translocation factor (<0.04) showed that Ag was mainly retained in the roots. The 1 µM Ag concentration increased the level of low-molecular-weight organic acids (LMWOAs), while 10 µM Ag depleted these compounds in the roots. The increased concentration of Ag(I) elevated the accumulation of phytochelatins (PCs) in the roots and reduced glutathione (GSH) in the shoots (but not in the roots). At 1 µM, Ag(I) elevated the level of phenolic and triterpene acids, while the 10 µM Ag treatment increased the carlina oxide content in the roots. The obtained results indicate an alteration of metabolic pathways of C. acaulis to cope with different levels of Ag(I) stress. Our data imply that the intracellular binding of Ag(I) and nonenzymatic antioxidants contribute to the protection against low concentrations of Ag ions.