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Silver nanoparticles (AgNPs) have been implemented in a wide range of commercial products, resulting in their unregulated release into aquatic as well as terrestrial systems. This raises concerns over their impending environmental effects. Once released into the environment, they are prone to various transformation processes that modify their reactivity. In order to increase AgNP stability, different stabilizing coatings are applied during their synthesis. However, coating agents determine particle size and shape and influence their solubility, reactivity, and overall stability as well as their behavior and transformations in the biological medium. In this review, we attempt to give an overview on how the employment of different stabilizing coatings can modulate AgNP-induced phytotoxicity with respect to growth, physiology, and gene and protein expression in terrestrial and aquatic plants and freshwater algae.

The harmful effects of silver nanoparticles (AgNPs) have been confirmed in many organisms, but the mechanism of their toxicity is not yet fully understood. In biological systems, AgNPs tend to aggregate and dissolve, so they are often stabilized by coatings that influence their physico-chemical properties. In this study, the effects of AgNPs with different coatings [polyvinylpyrrolidone (PVP) and cetyltrimethylammonium bromide (CTAB)] on oxidative stress appearance and proteome changes in tobacco (

Antimicrobial properties of silver and enhanced reactivity when applied in the nanoparticle form (AgNPs) led to their growing utilization in consumer products. Consequently, their increasing release into water or soil represents a potential environmental hazard and poses an indirect threat to human health. AgNP phytotoxic effects have been mainly attributed to the excess generation of reactive oxygen species (ROS), leading to the induction of oxidative stress [1]. However, most studies so far have been performed in vitro and at the whole plant or whole organ level, where oxidative stress symptoms were observed after plant exposure to stress conditions was long enough to produce extensive cell damage. In this work, detached roots of in vitro grown tobacco (Nicotiana tabacum) plants were exposed for 24 h to either AgNPs stabilized with polyvinylpyrrolidone (PVP) coating or ionic silver (AgNO3), applied in the 100 μM concentration with the aim to investigate in situ early physiological responses as first signs of stressful conditions. Generation of ROS in root cells was monitored by confocal laser scanning microscope (Leica TCS SP8) using highly sensitive and specific fluorescent probes: dihydroethidium (DHE), to detect superoxide radical (O2 –), and 2’, 7’-dichlorofluorescein-diacetate (H2DCF-DA), to detect hydrogen peroxide (H2O2) [2]. Moreover, monochlorobimane (MCB) was applied for the detection of glutathione (GSH), an important constituent of the cell antioxidant defence [3]. Additionally, propidium iodide (PI) was used as a counterstain to verify cell viability. The results showed an increased amount of H2O2 and O2 – and a decreased amount of GSH in roots exposed to both types of treatments in comparison to control, which was accompanied with an increased number of dead cells detected with PI. All observed changes were more prominent upon AgNO3- exposure compared to AgNPs. AgNPs were visualized within root cells upon both types of treatments by observing reflection and transmission with the excitation light source of 476 nm, and by employing a longer excitation wavelength (760 nm) of a multiphoton pulsed laser at which AgNP exhibit fluorescence properties. This suggests that not only AgNPs can enter roots cells, but also new AgNPs are being synthesized upon exposure to AgNO3. Fluorescence lifetime imaging microscopy (FLIM) revealed that the observed reflective and luminescent particles have a relatively short fluorescence lifetime, which could distinguish them from the natural compounds of plant cells. AgNPs were mostly found attached to the root surface and inside root hairs. Employment of transmission electron microscope (TF20, FEI Tecnai G2) coupled with energydispersive X-ray (EDX) detector confirmed AgNP localization in root cells. In conclusion, AgNPs and AgNO3 not only compromised cellular redox-homeostasis, but possibly caused cell necrosis, while different level of impact was observed depending on the form of the applied silver.

We report a plant (Beta vulgaris L. subsp. vulgaris.) cell culture-mediated reduction of prochiral 1-(3,4-dimethylphenyl)ethanone into the chiral alcohol (1R)-1-(3,4-dimethylphenyl)ethanol in natural deep eutectic solvents (NADES). To the best of our knowledge, this is the first report on plant culture cell behaviour during incubation in these solvents, where the novelty is transformation in callus culture. Three different choline chloride-based NADES (aqueous solutions containing 30, 50 and 80 % water [w/w]) containing sugar (glucose) or polyalcohols (glycerol and ethylene glycol) were screened for conversion and enantiomeric excess during the bioreduction. Both the conversion and the enantiomeric excess differed considerably when using different hydrogen bond donors, with the (R)-alcohol configuration predominating in the reactions conducted in most NADES. Changing the water content in NADES also altered the enantioselectivity. Testing the biocompatibility of NADES with sugar beet cell cultures revealed that NADES cause permeabilisation of cell membranes, leading to stress conditions that change plant metabolism. The potential for recycling and reusing plant biomass was tested for sugar beet cell cultures. The results indicate that recycling may be possible after 3–7 days of incubation, but longer incubations lead to too high a toxicity to cellular metabolism.

Optically active chiral building molecular blocks are widely used as intermediates in the production of drugs, organic chemicals, agricultural chemicals and other fine chemicals. As the conventional, environmentally hazardous chemical synthesis is expensive and extremely complicated, there is a rising need to introduce environmentally friendly approaches into the preparation of various commercial products. Herein, two tools of green chemistry were used: performing reactions by biocatalysis and the use of alternative green solvents – natural deep eutectic solvents (NADES). For that purpose two plant callus cultures - sugar beet and cactus were used, due to stereoselectivity of the plant enzymes, as biocatalysts for the asymmetric reduction of 1- (3, 4)-dimethylphenyl)ethanone (DMPA) into corresponding optically active 1-(3, 4- dimethylphenyl)ethanol in choline chloride- based NADES containing glucose, glycerol or ethylene glycol as hydrogen bond donor with 30%, 50% or 80% (v/v) of water. The efficiency of proposed biocatalytic reaction was monitored for both conversion and enantiomeric excess of reaction, and it was found to differ with the type of hydrogen bond donor and water content in NADES. Interestingly, for asymmetric reduction of DMPA with sugar beet plant culture performed in water and cactus plant culture performed in water and NADES containing 80% (v/v) of water, high enantioselectivity giving the (S) alcohol was observed, indicating that the reaction follows Prelog’s rule, while in other cases (R) alcohol was predominate enantiomer. Additionally, biocompatibility of NADES with plant callus cultures was studied for 3 weeks by monitoring morphology and viability of plant cells as well as by measuring stress enzymes and metabolite molecules.

Green chemistry is a prevention approach to designing products and processes that minimize the use of materials hazardous to human health and environment. Biocatalysis, green solvents, reducing energy consumption by using alternative energy sources (e.g. microwave, ultrasound) are most important tools of green chemistry. The biocatalysis (whole cells, cell extracts, or purified enzymes) has the ability to catalyse organic reactions in the high chemo-, regio-, and stereoselectivity under mild reaction conditions and therefore represents an environment-friendly method of performing reactions that are known to require highly acidic or alkaline levels, high energy consumption for heating or even highly toxic metal catalysts. During the last 10 years, in order to find an alternative to conventional organic solvents, natural deep eutectic solvents (NADES) have started to be assessed as tools for biocatalysis, either as solvents or as separative agents, to overcome challenging workup procedures. A number of enzymes have shown enhanced activity and stability in the presence of cholinium-based NADES. The possibility to design an optimal NADES for each specific biocatalytic reaction system allows to improve substrate/product solubility ; enhance enzyme activity, enantioselectivity, regioselectivity and stability ; or to tailor the reaction rate. Herein, the behavior of industrial biocatalyst, Candida antarctica lipase B, carrot root and yeast Saccharomyces cerevisiae in the asymmetric hydrolysis of prochiral compounds and asymmetric reduction of prochiral ketones in natural deep eutectic solvents was studied. The effects of NADES on the synthetic activity and enantioselectivity of selected biocatalysts (as solvents, co- solvents or immiscible second phase), as well as some key parameters of processes involving them, will be presented.