Investigating the Production of Antimicrobial Nanoparticles by Chlorella vulgaris and the Link to Its Loss of Viability

Chlorella vulgaris from Al-Ahsa, KSA was proved to be an active silver and gold nanoparticle producer. Nanogold and nanosilver particles were characterized using UV-visible spectroscopy, Fourier-transform infrared spectroscopy, and scanning electronmicroscopy. Both nanoparticles were used in the antimicrobial bioassay. The two nanoparticles showed antibacterial activities, with the silver nanoparticles being the most effective. To investigate the argumentative nature of their biosynthesis (i.e., whether it is a biotic or abiotic process), we isolated total ribonucleic acid RNA as an indicator of vitality. RNA was completely absent in samples taken after one week of incubation with silver nitrate and even after one or two days. However, successful extraction was only achievable in samples taken after incubation for one and four hours with silver nitrate. Most importantly, the gel image showed recognizable shearing of the nucleic acid after 4 h as compared to the control. An assumption can be drawn that the synthesis of nanoparticles may start biotically by the action of enzyme(s) and abiotically by action of reducing entities. Nonetheless, with prolonged incubation, excessive nanoparticle accumulation can be deadly. Hence, their synthesis continues abiotically. From the RNA banding profile, we suggest that nanosilver production starts both biotically and abiotically in the first few hours of incubation and then continues abiotically. Nanosilver particles proved to have more of an antimicrobial impact than nanogold and hence are recommended for different applications as antibacterial agents.

Can Ethylene Inhibitors Enhance the Success of Olive Somatic Embryogenesis?

An efficient in vitro morphogenesis, specifically through somatic embryogenesis, is considered to be a crucial step for the application of modern biotechnological tools for genetic improvement in olive (Olea europaea L.). The effects of different ethylene inhibitors, i.e., cobalt chloride (CoCl2), salicylic acid (SA), and silver nitrate (AgNO3), were reported in the cyclic somatic embryogenesis of olive. Embryogenic callus derived from the olive immature zygotic embryos of the cultivar Leccino, was transferred to the expression ECO medium, supplemented with the ethylene inhibitors at 20 and 40 µM concentrations. Among these, the maximum number of somatic embryos (18.6) was obtained in media containing silver nitrate (40 µM), followed by cobalt chloride (12.2 somatic embryos @ 40 µM) and salicylic acid (40 µM), which produced 8.5 somatic embryos. These compounds interfered on callus traits: white friable embryogenic calli were formed in a medium supplemented with 40 µM cobalt chloride and salicylic acid; in addition, a yellow-compact embryogenic callus appeared at 20 µM of all the tested ethylene inhibitors. The resulting stimulatory action of silver nitrate among all the tested ethylene inhibitors on somatic embryogenesis, clearly demonstrates that our approach can efficiently contribute to the improvement of the current SE protocols for olive.

The Erroneous Appearance of Silver Nitrate on CT Imaging in Patients with Severe Otitis Externa; A Case Series

Introduction Silver nitrate is commonly used within otolaryngology to treat granulation tissue in severe otitis externa. It appears radio-opaque on CT (computed tomography) imaging and therefore can mimic bony fragments and foreign bodies. This is particularly cumbersome when the phenomena correlates to the clinical complaint. Discussion We report two cases of 73-year-old and 75-year-old males who presented with chronic otalgia and discharge. Granulation tissue in the external auditory canal was identified and chemically cauterised with silver nitrate. Subsequent CT petrous bones demonstrated an unidentified foreign body in the canal with extensive soft tissue swelling giving an impression of a wick in situ and “minor bony erosion in the left external acoustic canal” respectively. An additional CT of a 57-year-old female who had been treated with silver nitrate for granulomatous tissue reported “multiple highly radiopaque foci in the external auditory canal, suggestive of foreign body”. Though relatively unknown, this phenomenon has been reported in literature. However, there are few reports of silver nitrate artefacts in CT images of the head no cases in the context of otitis externa. Our patients avoided further imaging or surgery following clarification with the radiologists and symptomatic improvement with long-term intravenous antibiotics. Conclusion Given the prevalence of CT imaging and cauterization in otolaryngology, we recommend contemporaneously documenting the use of silver nitrate and highlighting this on request forms to avoid alarming erroneous reports, unnecessary investigation and surgical procedures. We also recommend, where clinically acceptable, to use silver nitrate prior to imaging.

A Physiological behavior and tolerance of Lactuca sativa to lead nitrate and silver nitrate heavy metals

This study goal to evaluate the effects of different concentrations of lead (Pb) and silver (Ag) on germination, initial growth and anatomical alterations of Lactuca sativa L. Plants use various mechanisms to reduce the impacts caused by anthropic action, such as xenobiotic elements of soils and water contaminated by heavy metals. These metals were supplied as lead nitrate and silver nitrate and the following treatments were established: control for both metals, maximum dose of heavy metals, for arable soils, allowed by the National Council of the Environment (Ag = 25 mg. Kg-1, Pb = 180 mg. Kg-1), double (Ag = 50 mg. Kg-1, Pb = 360 mg. Kg-1) and triple (Ag = 75 mg. Kg-1, Pb = 540 mg. Kg -1) of this dosage. Vigor and germination tests of the seeds and possible anatomical changes in the leaves and roots of lettuce plants were performed. The species showed a high capacity to germinate under Pb and Ag stress, and the germination was never completely inhibited; however, the germination decreased with increasing Pb concentrations, but not under Ag stress. The use of increasing doses of metals reduced seed vigor and increased chlorophyll content. An increase in biomass was also observed in plants from treatments submitted to Pb. The phytotoxic effects of metals were more pronounced at 15 days after sowing. Anatomically, L. sativa was influenced by metal concentrations, and had a reduction of up to 79.9% in root epidermis thickness at the highest Pb concentration, although some structures did not suffer significant changes. The results suggest that L. sativa presents tolerance to high concentrations of heavy metals, showing possible mechanisms to overcome the stress caused by these metals. In this research lettuce possibly used the mechanism of exclusion of metals retaining Pb and Ag in the roots preserving the photosynthetic apparatus in the aerial part of the plants. In general, the chemical element Pb was more toxic than Ag, in these experimental conditions.

One-pot green synthesis of antimicrobial chitosan derivative nanocomposites to control foodborne pathogens

This study aimed to show the efficacy of the one-pot green biosynthesis of nanocomposites as effective antimicrobial agents based on a water-soluble biodegradable polysaccharide and silver nitrate (AgNO3).

Nano Ag/AgCl wires photocatalyzed hydrogen production and transfer hydrogenation of Knoevenagel-type products

Investigation of the relationship between the morphology of Ag/AgCl nanostructured composites with their catalytic performance was reported. The concentration ratio of silver nitrate and hydrochloric acid was controlled to produce...

Facile Route to Effective Antimicrobial Aluminum Oxide Layer Realized by Co-Deposition with Silver Nitrate

The emergence and spreading of the SARS-CoV-2 pandemic has forced the focus of attention on a significant issue: the realization of antimicrobial surfaces for public spaces, which do not require extensive use of disinfectants. Silver represents one of the most used elements in this context, thanks to its excellent biocidal performance. This work describes a simple method for the realization of anodized aluminum layers, whose antimicrobial features are ensured by the co-deposition with silver nitrate. The durability and the chemical resistance of the samples were evaluated by means of several accelerated degradation tests, such as the exposure in a salt spray chamber, the contact with synthetic sweat and the scrub test, highlighting the residual influence of silver in altering the protective behavior of the alumina layers. Furthermore, the ISO 22196:2011 standard was used as the reference protocol to set up an assay to measure the effective antibacterial activity of the alumina-Ag layers against both Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) bacteria, even at low concentrations of silver. Finally, the Ag-containing aluminum oxide layers exhibited excellent antimicrobial performances also following the chemical–physical degradation processes, ensuring good durability over time of the antimicrobial surfaces. Overall, this work introduces a simple route for the realization of anodized aluminum surfaces with excellent antibacterial properties.

DETERMINATION OF OPTIMAL PARAMETERS FOR SYNTHESIS OF SILVER NANOPARTICLES STABILIZED WITH POLYETHYLENE GLYCOL

В рамках данной работы представлены результаты исследования влияния концентраций стабилизатора и прекурсора на процесс синтеза наночастиц серебра. В качестве прекурсора использован нитрат серебра, а в качестве стабилизатора -полиэтиленгликоль с молекулярной массой от 200 до 600 Да. Синтез осуществляли методом химического восстановления в водной среде. Полученные образцы исследовали фотонно-корреляционной спектроскопией и спектрофотометрией. Установлено наличие характеристической полосы поглощения на 400 нм в спектрах поглощения всех образцов наноразмерного серебра, стабилизированного полиэтиленгликолем, что обусловлено возникновением поверхностного плазмонного резонанса у металлических наночастиц серебра. Также установлено, что при наибольшей и наименьшей концентрации стабилизатора, равных, соответственно, 0. 005 и 0,1 мас. %, в реакционной системе наблюдается формирование крупных частиц серебра со средним гидродинамическим радиусом от 132 до 1900 нм. В результате определены оптимальные параметры синтеза агрегативно устойчивых наночастиц серебра: концентрация нитрата серебра С (AgNO) = 0,05 M и концентрация полиэтиленгликоля, равная 0,01 - 0,05 %. Проведено компьютерное квантовохимическое моделирование. Установлено, что энергетически выгодным является взаимодействие атома серебра с концевой гидроксогруппой в молекуле полиэтиленгликоля в элементарном акте взаимодействия при стабилизации наночастиц серебра данным полимером. Данный тип взаимодействия характеризуется абсолютной химической жесткостью, равной ƞ = 0,146 эВ, и внутренней энергией E = -2048,34 ккал / моль. Within the framework of this work, the results are presented of a study of the effect of the concentrations of the stabilizer and precursor on the synthesis of silver nanoparticles. Silver nitrate was used as a precursor, and polyethylene glycol with a molecular weight from 200 to 600 Da was used as a stabilizer. The synthesis was carried out by the method of chemical reduction in an aqueous medium. The obtained samples were investigated by photon correlation spectroscopy and spectrophotometry. The presence of a characteristic absorption band at 400 nm in the absorption spectra of all samples of nanosized silver stabilized with polyethylene glycol was established, which is due to the appearance of surface plasmon resonance in metallic silver nanoparticles. It was also found that at the highest and lowest concentration of the stabilizer, equal, respectively, 0,005 and 0,1 mass. %, the formation of large silver particles with an average hydrodynamic radius from 132 to 1900 nm is observed in the reaction system. As a result, the optimal parameters for the synthesis of aggregatively stable silver nanoparticles were determined: the concentration of silver nitrate C(AgNO) = 0,05 M and the concentration of polyethylene glycol equal to 0,01 - 0,05 %. Computer quantum-chemical modeling is carried out. It is found that the interaction of the silver atom with the terminal hydroxogroup in the polyethylene glycol molecule in the elementary act of interaction during the stabilization of silver nanoparticles by this polymer is energetically advantageous. This type of interaction is characterized by an absolute chemical hardness equal to ƞ = 0,146, and an internal energy of E = -2048,34 kcal / mol.

IMPACT OF VARIOUS PRESERVATIVE SOLUTIONS ON VASE LIFE AND POST-HARVEST QUALITY OF CUT ROSES

Short vase life and post-harvest losses of cut flowers are major threat to floriculture industry. There are different preservative solutions that have been used to extend the post-harvest life of cut flowers. Hence, this study was executed at Floriculture laboratory of Ayub Agricultural Research Institute, Faisalabad during 2018-2020 to explore the efficacy of different preservative solutions on vase life and post-harvest quality of cut roses. There were 6 treatments viz, (T1= Distilled water, T2= Silver nitrate @ 100 ppm, T3= 8-Hydroxyquiroline citrate @ 100 ppm, T4= Sodium thiosulphate @100 ppm, T5= Sodium benzoate @100 ppm, T6= Sucrose @ 40 g/L) and two rose cultivars Kardinal and Gold medal. The experiment was arranged according to complete randomized design (CRD). Results designated that longest vase life (15 days), maximum soluble solid contents (9.3 Brix) and longest opening period (7.4 days) were acquired with silver nitrate @100 ppm solution while maximum flower size (6.77 cm2) and largest head diameter (8.6 cm) were achieved with sodium thiosulphate when applied at the rate of 100 ppm in cultivar Kardinal. All other chemical solutions also displayed positive effects. Keeping in view the remarkable impact of Silver nitrate on vase life and quality of cut roses, it is recommended for commercial growers and cut flower industry for preservation of cut roses for longer time.