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Secondary, or amyloid protein A (AA), amyloidosis is a complication of chronic inflammatory diseases, both infectious and noninfectious. AA constitutes the insoluble fibrils, which are deposited in different organs, and is a major N-terminal part of the acute phase protein serum AA. It is not known why only some patients with chronic inflammation develop AA amyloidosis. Nucleation is a widely accepted mechanism in amyloidogenesis. Preformed amyloid-like fibrils act as nuclei in amyloid fibril formation in vitro, and AA amyloid fibrils and synthetic amyloid-like fibrils also may serve as seed for fibril formation in vivo. In addition to amyloid fibrils, there is a variety of similar nonmammalian protein fibrils with β-pleated structure in nature. We studied three such naturally occurring protein fibrils: silk from Bombyx mori, Sup35 from Saccharomyces cerevisiae, and curli from Escherichia coli. Our results show that these protein fibrils exert amyloid-accelerating properties in the murine experimental AA amyloidosis, suggesting that such environment factors may be important risk factors in amyloidogenesis.

We report a previously unrecognized mechanism for the prolonged action of biocidal agents, which we denote as the zombies effect: biocidally-killed bacteria are capable of killing living bacteria. The concept is demonstrated by first killing Pseudomonas aeruginosa PAO1 with silver nitrate and then challenging, with the dead bacteria, a viable culture of the same bacterium: Efficient antibacterial activity of the killed bacteria is observed. A mechanism is suggested in terms of the action of the dead bacteria as a reservoir of silver, which, due to Le-Chatelier's principle, is re-targeted to the living bacteria. Langmuirian behavior, as well as deviations from it, support the proposed mechanism.

It is generally accepted that antibacterial properties of Ag nanoparticles (AgNPs) are dictated by their dissolved fraction. However, dissolution-based concept alone does not fully explain the toxic potency of nanoparticulate silver compared to silver ions. Herein, we demonstrated that the direct contact between bacterial cell and AgNPs' surface enhanced the toxicity of nanosilver. More specifically, cell-NP contact increased the cellular uptake of particle-associated Ag ions - the single and ultimate cause of toxicity. To prove that, we evaluated the toxicity of three different AgNPs (uncoated, PVP-coated and protein-coated) to six bacterial strains: Gram-negative Escherichia coli, Pseudomonas fluorescens, P. putida and P. aeruginosa and Gram-positive Bacillus subtilis and Staphylococcus aureus. While the toxicity of AgNO3 to these bacteria varied only slightly (the 4-h EC50 ranged from 0.3 to 1.2 mg Ag/l), the 4-h EC50 values of protein-coated AgNPs for various bacterial strains differed remarkably, from 0.35 to 46 mg Ag/l. By systematically comparing the intracellular and extracellular free Ag(+) liberated from AgNPs, we demonstrated that not only extracellular dissolution in the bacterial test environment but also additional dissolution taking place at the particle-cell interface played an essential role in antibacterial action of AgNPs. The role of the NP-cell contact in dictating the antibacterial activity of Ag-NPs was additionally proven by the following observations: (i) separation of bacterial cells from AgNPs by particle-impermeable membrane (cut-off 20 kDa, ∼4 nm) significantly reduced the toxicity of AgNPs and (ii) P. aeruginosa cells which tended to attach onto AgNPs, exhibited the highest sensitivity to all forms of nanoparticulate Ag. Our findings provide new insights into the mode of antibacterial action of nanosilver and explain some discrepancies in this field, showing that \"Ag-ion\" and \"particle-specific\" mechanisms are not controversial but, rather, are two faces of the same coin.

Key message Atropa acuminata aqueous leaf extract biosynthesized silver nanoparticles showed strong antioxidant, anticancerous (HeLa cells) and anti-inflammatory activities. Besides, this bio syn-AgNP also proved effective against mosquito vectors causing malaria, dengue and filariasis. Present study highlights eco-friendly and sustainable approach for the synthesis of silver nanoparticles (AgNP) using aqueous leaf extract of A. acuminata , a critically endangered medicinal herb. The addition of 1 mM silver nitrate to aqueous leaf extract resulted in the synthesis of AgNP when solution was heated at 60 °C for 30 min at pH 7. Absorption band at 428 nm, as shown by UV–Vis spectroscopy confirmed the synthesis of AgNP. XRD patterns revealed the crystalline nature of AgNP and TEM analysis showed that most of the nanoparticles were spherical in shape. Zeta potential of AgNP was found to be − 33.5 mV which confirmed their high stability. FT-IR investigations confirmed the presence of different functional groups involved in the reduction and capping of AgNP. The synthesized AgNP showed effective DPPH (IC 50 —16.08 µg/mL), H 2 O 2 (IC 50 —25.40 µg/mL), and superoxide (IC 50 —21.12 µg/mL) radical scavenging activities. These plant-AgNP showed significant inhibition of albumin denaturation (IC 50 —12.98 µg/mL) and antiproteinase activity (IC 50 —18.401 µg/mL). Besides, biosynthesized AgNP were found to have strong inhibitory effect against a cervical cancer (HeLa) cell line (IC 50 —5.418 µg/mL) as well as larvicidal activity against 3rd instar larvae of Anopheles stephensi (LC 50 —18.9 ppm, LC 90 —40.18 ppm), Aedes aegypti (LC 50 —12.395 ppm, LC 90 —36.34 ppm) and Culex quinquefasciatus (LC 50 —17.76 ppm, LC 90 —30.82 ppm) and were found to be non-toxic against normal cell line (HEK 293), and a non-target organism ( Mesocyclops thermocyclopoides ). This is the first report on the synthesis of AgNP using aqueous leaf extract of A. acuminata , validating their strong therapeutic potential.

The detrimental impact of blood on the antimicrobial activity of AgNbO 3 particles was identified and investigated. It was observed that the impact is more severe in the case of lysed blood. The same phenomenon also operates in the case of commonly used silver salt, AgNO 3 . The inhibition was shown to be due to hemoglobin, but may be unrelated to the heme moiety. In an attempt to find additives to mitigate the inhibitory effect of hemoglobin, iron ions and the chelating agent, K 2 EDTA, were initially considered as potential candidates. Including ferric iron on the particles was shown to have a marginal effect, but supplying the medium with K 2 EDTA chelating agent, provided a better outcome for countering the deleterious impact of hemoglobin on AgNbO 3 activity. These findings may be relevant for adapting the silver compounds to applications such as wound dressings, where silver’s antimicrobial action would have to take place in a blood containing environment.

Theba pisana and Monacha cartusiana , both land snails, are agricultural pests that have caused significant losses in many orchards and fields in various areas of Egypt. In this study, the efficacy of nicotinamide, imidacloprid, and silver nitrate nanoparticles compounds compared to oxamyl were evaluated against these two snail species using residual film and poison bait techniques under laboratory and field conditions to identify alternative, more effective options to conventional pesticides. In addition, the genotoxicity impacts of these compounds on the tested snails were thoroughly investigated. Results showed that, for T. pisana , oxamyl exhibited the highest mortality rate, followed by nicotinamide and silver nitrate, with calculated LC 50 values of 0.028%, 0.049%, and 0.120% for residual film technique and 0.546%, 0.971%, and 1.333% for poison bait technique. Similarly, for M. cartusiana , oxamyl exhibited the highest toxicity, followed by nicotinamide and silver nitrate, with LC 50 values of 0.054%, 0.063 and 0.103% in residual film method, While in the poison bait method, oxamyl showed the highest toxicity, followed by silver nitrate and nicotinamide with LC 50 values of 0.273%, 1.150 and 1.204, respectively. Imidacloprid showed the lowest efficacy in both species with LC 50 values of (0.19, 0.14%) and (1.57, 1.48%) for residual film and baits techniques, respectively. The field evaluation of tested compounds against T. pisana and M. cartusiana snails using poisonous baits revealed varying effectiveness in reducing snail populations. Oxamyl showed the highest reduction rates, with 46.31%, 63.63%, and 90.85% for T. pisana and 29.47%, 63.92%, and 92.13% for M. cartusiana after 1, 7, and 21 days of treatment, respectively. Nicotinamide and silver nitrate nanoparticles were also effective, reducing populations by 81.71% and 72.83% for T. pisana and 92.62% and 84.95% for M. cartusiana after 21 days. Imidacloprid compound resulted in the lowest reductions, with 60.64 and 63.26% for two species, respectively. Respecting molecular diagnosis RAPD- PCR, the results demonstrated that the presence of polymorphism in the two types of snails treated with tested compounds.

Background The biochemical and growth changes resulting from exposure of basil ( Ocimum basilicum L.) seedlings to silver nanoparticles and silver were investigated. Over a two-week period, seedlings were exposed to different concentrations (0, 40, and 80 ppm) of silver nanoparticles and silver. Results Our findings revealed that at concentrations of 40 and 80 ppm, both silver nanoparticles and silver nitrate led to decreased weight, root and shoot length, as well as chlorophyll a and b content. Conversely, these treatments triggered an increase in key biochemical properties, such as total phenols, carotenoids and anthocyanins, with silver nanoparticles showing a more pronounced effect compared to silver nitrate. Moreover, the levels of malondialdehyde (MDA) and hydrogen peroxide (H 2 O 2 ) rose proportionally with treatment concentration, with the nanoparticle treatment exhibiting a more substantial increase. Silver content showed a significant upswing in both roots and leaves as treatment concentrations increased. Conclusions Application of varying concentrations of silver nanoparticles and silver nitrate on basil plants resulted in reduced growth and lower chlorophyll content, while simultaneously boosting the production of antioxidant compounds. Notably, anthocyanin, carotenoid, and total phenol increased significantly. However, despite this increase in antioxidant activity, the plant remained unable to fully mitigate the oxidative stress induced by silver and silver nanoparticles.

In this study, the callus of Carica papaya was treated with silver nitrate solution to form silver nanoparticles which were later used as anti-contaminant substances in micropropagation media on C. nocturnum (cestrum, night queen) and Rosa indica (rose) in tissue culture medium. For this purpose, the rose and cestrum explants were cultured using murashige and skoog (MS) media containing 2 mg/l benzylaminopurine (BAP). After micropropagation of the shoots, different concentrations of biogenically synthesized silver nanoparticles (AgNPs) i.e., 2, 3, and 5 ppm were added into the MS media, for dose optimization. The morphology of tissue-cultured plants in control and experimental has been studied and compared through fluorescent microscopy and Scanning Electron Microscopy (SEM). The cells, tissues, and vascular bundles of C. nocturnum and rose tissue culture plants were studied in both control and treated plants. AgNPs added at a concentration of 5 ppm to the tissue culture medium of both test plants were safe and effective in controlling the contamination and the bacterial and fungal attack in the tissue culture medium was reduced; it gave the highest percentage of survived plants in both the rose and the cestrum plant. No significant difference was observed in the chlorophyll content of the plants maintained on treatment medium having AgNPs concentration of 5 ppm and the control plants maintained on medium without nanoparticles. The molecular assessment of the stress impact of AgNPs treatment was analyzed through expression of the SAND and PP2A housekeeping genes in treated plants and control plants by comparing their mRNA profile on real-time PCR, and the results showed equal expression of SAND and PP2A in both the control and treated plants. This study proves that low amounts of bio-synthesized silver nanoparticles when supplied in tissue culture media can act as an anti-contaminant in rose and cestrum in vitro cultures without affecting its morphology, physiology, and genetics.

Plants that synthesize bioactive compounds that have high antioxidant value and elicitation offer a reliable in vitro technique to produce important nutraceutical compounds. The objective of this study is to promote the biosynthesis of these phenolic compounds on a large scale using elicitors in date palm cell suspension culture. Elicitors such as pectin, yeast extract (YE), salicylic acid (SA), cadmium chloride (CdCl2), and silver nitrate (AgNO3) at 50, 100, and 200 mg/L concentrations are used. The effects of elicitors on cell culture were determined in terms of biomass [packed cell volume (PCV), fresh and dry weight], antioxidant activity, and phenolic compounds (catechin, caffeic acid, kaempferol, apigenin) were determined using high-performance liquid chromatography (HPLC). Results revealed that enhanced PCV (12.3%), total phenolic content [317.9 ± 28.7 mg gallic acid equivalents (GAE)/100 g of dry weight (DW)], and radical scavenging activity (86.0 ± 4.5%) were obtained in the 50 mg/L SA treated cell culture of Murashige and Skoog (MS) medium. The accumulation of optimum catechin (26.6 ± 1.3 µg/g DW), caffeic acid (31.4 ± 3.8 µg/g DW), and kaempferol (13.6 ± 1.6 µg/g DW) was found in the 50 mg/L SA-treated culture when compared to the control. These outcomes could be of great importance in the nutraceutical and agronomic industries.

HDL from healthy humans and lean mice inhibits palmitate-induced adipocyte inflammation; however, the effect of the inflammatory state on the functional properties of HDL on adipocytes is unknown. Here, we found that HDL from mice injected with AgNO3 fails to inhibit palmitate-induced inflammation and reduces cholesterol efflux from 3T3-L1 adipocytes. Moreover, HDL isolated from obese mice with moderate inflammation and humans with systemic lupus erythematosus had similar effects. Since serum amyloid A (SAA) concentrations in HDL increase with inflammation, we investigated whether elevated SAA is a causal factor in HDL dysfunction. HDL from AgNO3-injected mice lacking Saa1.1 and Saa2.1 exhibited a partial restoration of antiinflammatory and cholesterol efflux properties in adipocytes. Conversely, incorporation of SAA into HDL preparations reduced antiinflammatory properties but not to the same extent as HDL from AgNO3-injected mice. SAA-enriched HDL colocalized with cell surface-associated extracellular matrix (ECM) of adipocytes, suggesting impaired access to the plasma membrane. Enzymatic digestion of proteoglycans in the ECM restored the ability of SAA-containing HDL to inhibit palmitate-induced inflammation and cholesterol efflux. Collectively, these findings indicate that inflammation results in a loss of the antiinflammatory properties of HDL on adipocytes, which appears to partially result from the SAA component of HDL binding to cell-surface proteoglycans, thereby preventing access of HDL to the plasma membrane.