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In this study, hydrogels were produced using a Schiff base reaction between two hyaluronic acid derivatives: one containing aldehyde groups (HA-Ald) and the other holding a diethylenetriamine with terminal amino groups (HA-DETA). The DETA portion promotes the in situ growth, complexation, and stabilization of silver nanoparticles (AgNPs), eliminating the need for external reducing agents. The reaction between HA-DETA and HA-Ald leads to the formation of imine bonds, which results in dynamically pH-responsive cross-linking. While the DETA capping ability helped in embedding the AgNPs, the on/off pH environmental responsivity of the hydrogel allows for a controlled and on-demand release of the drug, mainly when bacterial infections cause pH variation of the wound bed. The injectable hydrogels resulted in being highly compatible in contact with blood red cells, fibroblasts, and keratinocytes and capable of having a proliferative effect on an in vitro wound scratch model. The pH-responsive hydrogels showed proper antibacterial activity againstPseudomonas aeruginosaandStaphylococcus aureus, common bacterial strains presented in wound infections. Finally, in vivo wound model studies demonstrated an overall speeding up in the wound healing rate and advanced wound conditions in the experimental group treated with the hydrogels compared to control samples.

Background: Adverse outcome pathways (AOPs) are conceptual frameworks that organize knowledge about biological interactions and toxicity mechanisms. They present a sequence of events commencing with initial interaction(s) of a stressor, which defines the perturbation in a biological system (molecular initiating event, MIE), and a dependent series of key events (KEs), ending with an adverse outcome (AO). AOPs have recently become the subject of intense studies in a view to better understand the mechanisms of nanomaterial (NM) toxicity. Silver nanoparticles (Ag NPs) are one of the most explored nanostructures and are extensively used in various application. This, in turn, has increased the potential for interactions of Ag NPs with environments, and toxicity to human health. The aim of this study was to construct a putative AOPs (pAOP) related to reproductive toxicity of Ag NPs, in order to lay the groundwork for a better comprehension of mechanisms affecting both undesired toxicity (against human cell) and expected toxicity (against microorganisms). Methods: PubMed and Scopus were systematically searched for peer-reviewed studies examining reproductive toxicity potential of Ag NPs. The quality of selected studies was assessed through ToxRTool. Eventually, forty-eight studies published between 2005 and 2022 were selected to identify the mechanisms of Ag NPs impact on reproductive function in human male. The biological endpoints, measurements, and results were extracted from these studies. Where possible, endpoints were assigned to a potential KE and an AO using expert judgment. Then, KEs were classified at each major level of biological organization. Results: We identified the impairment of intracellular SH-containing biomolecules, which are major cellular antioxidants, as a putative MIE, with subsequent KEs defined as ROS accumulation, mitochondrial damage, DNA damage and lipid peroxidation, apoptosis, reduced production of reproductive hormones and reduced quality of

The widespread use of silver nanoparticles (Ag NPs) in food and consumer products suggests the relevance of human oral exposure to these nanomaterials (NMs) and raises the possibility of adverse effects in the gastrointestinal tract. The aim of this study was to investigate the toxicity of Ag NPs in a human intestinal cell line, either uncoated or coated with polyvinylpyrrolidone (Ag PVP) or hydroxyethylcellulose (Ag HEC) and digested in simulated gastrointestinal fluids. Physicochemical transformations of Ag NPs during the different stages of in vitro digestion were identified prior to toxicity assessment. The strategy for evaluating toxicity was constructed on the basis of adverse outcome pathways (AOPs) showing Ag NPs as stressors. It consisted of assessing Ag NP cytotoxicity, oxidative stress, genotoxicity, perturbation of the cell cycle and apoptosis. Ag NPs caused a concentration-dependent loss of cell viability and increased the intracellular level of reactive oxygen species as well as DNA damage and perturbation of the cell cycle. In vitro digestion of Ag NPs did not significantly modulate their toxicological impact, except for their genotoxicity. Taken together, these results indicate the potential toxicity of ingested Ag NPs, which varied depending on their coating but did not differ from that of non-digested NPs.

Introduction: In recent years, there has been a resurgence in the use of traditional medicinal herbs, and as a result, pharmaceutical companies are investing heavily in developing natural medications derived from plants. Nanoparticles act in a number of potential ways and fields. Chemical synthesis of nanoparticles is no longer advantageous compared to plant-based synthesis. The current study uses a green method to create silver nanoparticles (AgNPs) utilizing flower extract. Materials and methods: The cytotoxic activity for gel was tested by the following convention proposed by Muzushima and Kabayashi with specific alterations. 0.05 mL of hibiscus and marigold of various fixations. Result: Using rosa and jasminum extract in the manufacture of silver nanoparticles, the nanoparticles showed remarkable antioxidant and anti-inflammatory activity. It was discovered that the cytotoxic effect was less harmful, demonstrating biocompatibility. Rosa jasminum extract of AgNps showed good anti-inflammatory efficacy in the EA and BSA assays. Conclusion: From our study we concluded that Silver nanoparticles were created using rosa and jasminum extract, and the nanoparticles displayed impressive cytotoxicity.

Nanoparticles are materials that measure from 1 to 100 nm of length. Currently, the antimicrobial property of silver nanoparticles is used by industries for the manufacture of beauty products and medicines. Nanoparticles can be synthesized from plants, algae or microorganisms, and they can also be obtained from combustion products. In this study, extracts of rosemary leaves (Rosmarinus officinalis L.) were used for the synthesis of silver nanoparticles (NPs-Ag) in order to produce an antimicrobial compound to be used as a fruit preservative. NPs-Ag were characterized qualitatively and quantitatively by phytochemical analysis and UV-VIS spectroscopy, showing an absorption in the range of 389-418 nm, which corresponds to their surface plasmon resonance. Furthermore, Scanning Electronic Microscopy was used to determine the size and morphology of the NPs-Ag, observing a spherical shape of 10 nm of diameter. Two bacterial strains were used in the antimicrobial tests, the Gram-negative (Escherichia coli) and the Gram-positive (Staphylococcus aureus) to verify the antimicrobial activity of the NPs-Ag. For E. coli, a better antibacterial activity was obtained with an inhibition halo of 3.21 mm. Subsequently, the NPs-Ag were used in apples to determine their use as a preservative, using beeswax smeared on the surface of the fruit as control, observing that synthesized NPs-Ag prolonged the maturation time of the fruits., As nanopartículas são materiais que podem medir entre 1 e 100 nm de comprimento, atualmente a propriedade antimicrobiana das nanopartículas de prata é utilizada pelas indústrias para fabricação de produtos de beleza e medicamentos. As nanopartículas podem ser sintetizadas a partir de plantas, algas ou microrganismos, e também podem ser obtidas como produtos de combustão. Neste estudo, extratos de folhas de alecrim (Rosmarinus officinalis L.) foram utilizados para a síntese de nanopartículas de prata (NPs-Ag) a fim de produzir um composto antimicrobiano a ser utilizado como conservante de frutas. As NPs-Ag foram caracterizadas qualitativa e quantitativamente por análise fitoquímica e espectroscopia UV-VIS, apresentando uma absorção na faixa de 389-418 nm, que corresponde à ressonância do plasmão superfícial. Além disso, a microscopia eletrônica de varredura foi utilizada para determinar o tamanho e morfologia das NPs-Ag, observando uma forma esférica de 10 nm de diâmetro. Nos testes antimicrobianos realizados foram utilizadas duas cepas bacterianas, uma gram-negativa (Escherichia coli) e uma gram-positiva (Staphylococcus aureus) para verificar a atividade antimicrobiana das NPs-Ag. Para E. coli, foi obtida uma melhor atividade antibacteriana com um halo de inibição de 3,21 mm. Posteriormente, as NPs-Ag foram utilizadas em maçãs para determinar seu uso como conservante, utilizando cera de abelha como controle espalhado na superfície dos frutos, observando-se que as nanopartículas sintetizadas estenderam o tempo de maturação dos frutos, Las nanopartículas son materiales que pueden llegar a medir entre 1 a 100 nm de longitud, y en la actualidad la propiedad antimicrobiana de las nanopartículas de plata es aprovechada por las industrias para la fabricación de productos de belleza y medicamentos. Las nanopartículas pueden ser sintetizadas a partir de plantas, algas o microorganismos, y también pueden ser obtenidas como productos de combustión. En este estudio se utilizaron extractos de las hojas de romero (Rosmarinus officinalis L.) para la síntesis de nanopartículas de plata (NPs-Ag) con la finalidad de producir un compuesto antimicrobiano para usarse como conservante de frutas. Las NPs-Ag se caracterizaron cualitativa y cuantitativamente mediante análisis fitoquímicos y espectroscopia UV-VIS, presentando una absorción en el rango de 389-418 nm, que corresponde a la resonancia de su plasmón superficial. Además, se empleó la microscopía electrónica de barrido para determinar el tamaño y morfología de las NPs-Ag, observándose una forma esférica de 10 nm de diámetro. Se emplearon dos cepas bacterianas en los ensayos antimicrobianos realizados, la gramnegativa (Escherichia coli) y la grampositiva (Staphylococcus aureus) para comprobar la actividad antimicrobiana de las NPs-Ag. Para E. coli se obtuvo una mejor actividad antibacteriana con un halo de inhibición de 3,21 mm. Posteriormente se usaron las NPs-Ag en manzanas para determinar su uso como conservante, usando la cera de abeja como control untada en la superficie de las frutas, observándose que las nanopartículas sintetizadas alargaron el tiempo de maduración de la frutas.

Nanoparticles are materials that measure from 1 to 100 nm of length. Currently, the antimicrobial property of silver nanoparticles is used by industries for the manufacture of beauty products and medicines. Nanoparticles can be synthesized from plants, algae or microorganisms, and they can also be obtained from combustion products. In this study, extracts of rosemary leaves (Rosmarinus officinalis L.) were used for the synthesis of silver nanoparticles (NPs-Ag) in order to produce an antimicrobial compound to be used as a fruit preservative. NPs-Ag were characterized qualitatively and quantitatively by phytochemical analysis and UV-VIS spectroscopy, showing an absorption in the range of 389-418 nm, which corresponds to their surface plasmon resonance. Furthermore, Scanning Electronic Microscopy was used to determine the size and morphology of the NPs-Ag, observing a spherical shape of 10 nm of diameter. Two bacterial strains were used in the antimicrobial tests, the Gram-negative (Escherichia coli) and the Gram-positive (Staphylococcus aureus) to verify the antimicrobial activity of the NPs-Ag. For E. coli, a better antibacterial activity was obtained with an inhibition halo of 3.21 mm. Subsequently, the NPs-Ag were used in apples to determine their use as a preservative, using beeswax smeared on the surface of the fruit as control, observing that synthesized NPs-Ag prolonged the maturation time of the fruits., As nanopartículas são materiais que podem medir entre 1 e 100 nm de comprimento, atualmente a propriedade antimicrobiana das nanopartículas de prata é utilizada pelas indústrias para fabricação de produtos de beleza e medicamentos. As nanopartículas podem ser sintetizadas a partir de plantas, algas ou microrganismos, e também podem ser obtidas como produtos de combustão. Neste estudo, extratos de folhas de alecrim (Rosmarinus officinalis L.) foram utilizados para a síntese de nanopartículas de prata (NPs-Ag) a fim de produzir um composto antimicrobiano a ser utilizado como conservante de frutas. As NPs-Ag foram caracterizadas qualitativa e quantitativamente por análise fitoquímica e espectroscopia UV-VIS, apresentando uma absorção na faixa de 389-418 nm, que corresponde à ressonância do plasmão superfícial. Além disso, a microscopia eletrônica de varredura foi utilizada para determinar o tamanho e morfologia das NPs-Ag, observando uma forma esférica de 10 nm de diâmetro. Nos testes antimicrobianos realizados foram utilizadas duas cepas bacterianas, uma gram-negativa (Escherichia coli) e uma gram-positiva (Staphylococcus aureus) para verificar a atividade antimicrobiana das NPs-Ag. Para E. coli, foi obtida uma melhor atividade antibacteriana com um halo de inibição de 3,21 mm. Posteriormente, as NPs-Ag foram utilizadas em maçãs para determinar seu uso como conservante, utilizando cera de abelha como controle espalhado na superfície dos frutos, observando-se que as nanopartículas sintetizadas estenderam o tempo de maturação dos frutos, Las nanopartículas son materiales que pueden llegar a medir entre 1 a 100 nm de longitud, y en la actualidad la propiedad antimicrobiana de las nanopartículas de plata es aprovechada por las industrias para la fabricación de productos de belleza y medicamentos. Las nanopartículas pueden ser sintetizadas a partir de plantas, algas o microorganismos, y también pueden ser obtenidas como productos de combustión. En este estudio se utilizaron extractos de las hojas de romero (Rosmarinus officinalis L.) para la síntesis de nanopartículas de plata (NPs-Ag) con la finalidad de producir un compuesto antimicrobiano para usarse como conservante de frutas. Las NPs-Ag se caracterizaron cualitativa y cuantitativamente mediante análisis fitoquímicos y espectroscopia UV-VIS, presentando una absorción en el rango de 389-418 nm, que corresponde a la resonancia de su plasmón superficial. Además, se empleó la microscopía electrónica de barrido para determinar el tamaño y morfología de las NPs-Ag, observándose una forma esférica de 10 nm de diámetro. Se emplearon dos cepas bacterianas en los ensayos antimicrobianos realizados, la gramnegativa (Escherichia coli) y la grampositiva (Staphylococcus aureus) para comprobar la actividad antimicrobiana de las NPs-Ag. Para E. coli se obtuvo una mejor actividad antibacteriana con un halo de inhibición de 3,21 mm. Posteriormente se usaron las NPs-Ag en manzanas para determinar su uso como conservante, usando la cera de abeja como control untada en la superficie de las frutas, observándose que las nanopartículas sintetizadas alargaron el tiempo de maduración de la frutas.

(1) Background: Wounds with damages to the subcutaneous are difficult to regenerate because of the tissue damages and complications such as bacterial infection. (2) Methods: In this study, we created burn wounds on pigs and investigated the efficacy of three biomaterials: polycaprolactone‐gelatin‐silver membrane (PCLGelAg) and two commercial burn dressings, Aquacel® Ag and UrgoTul™ silver sulfadiazine. In vitro long‐term antibacterial property and in vivo wound healing performance were investigated. Agar diffusion assays were employed to evaluate bacterial inhibition at different time intervals. Minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC) and time‐kill assays were used to compare antibacterial strength among samples. Second‐degree burn wounds in the pig model were designed to evaluate the efficiency of all dressings in supporting the wound healing process. (3) Results: The results showed that PCLGelAg membrane was the most effective in killing both Gram‐positive and Gram-negative bacteria bacteria with the lowest MBC value. All three dressings (PCLGelAg, Aquacel, and UrgoTul) exhibited bactericidal effect during the first 24 h, supported wound healing as well as prevented infection and inflammation. (4) Conclusions: The results suggest that the PCLGelAg membrane is a practical solution for the treatment of severe burn injury and other infection‐related skin complications.

This is a protocol to fabricate silver nanoparticle coated silica beads for optical trapping and surface enhanced Raman spectroscopy (SERS) measurement. (2021-01-20)

Metallic nanoparticles are small particles, with dimensions of less than 100 nm, which have unique characteristics. For example, the color of a nanoparticle solution is given by the surface plasmon resonance, in contrast to only absorbance of a molecule. Metallic nanoparticles have been used in the antiquity for the production of colored glass. Many of the medieval cathedral red windows are in fact, stained with gold nanoparticles. However, presenting just a red solution to a class and explaining that the solution contains gold nanoparticles can be disappointing as the red color can be obtained in many different ways without the need of nanoparticles. Something peculiar, like dichroism, can, on the other hand, shine the interest of an observer to the "nano-world". Dichroic nanoparticles show different colors when illuminated from the front (scattering) or from the back (transmission). This effect is unique for nanoparticles and nanostructures in general and can generate the "WOW"effect in class or during public demonstrations. In this article we present a simple synthesis of dichroic silver and gold nanoparticles. Solutions of such nanoparticles are a stunning visual media for demonstrations, outreach and engaging audience in the "nano"world.

The synthesis and adsorption potential of Cy-npAg, obtained by modification of raw montmorillonite clay (raw-Cy) with silver nanoparticle (npAg), was studied in this work. Optimization procedure, with respect to time, temperature and amount of deposit npAg, obtained either by reductive precipitation or ultraviolet irradiation, was performed using response surface methodology (RSM). The most efficient adsorbent, obtained by chemical reduction of silver ion with sodium borohydride, named Cy-npAg, was characterized in detail using Brunauer-Emmett-Teller, scanning electron microscopy, Fourier transform infrared spectroscopy and X-ray diffraction techniques, and point of zero charge determination. The Cy-npAg showed good adsorption capacity with respect to non-systemic organophosphate insecticide (diazinon) as well as of heavy metals ions (Cd2+ and Ni2+ ions), that is, 74.26, 62.33, and 35.49 mg g(-1), respectively, obtained from Langmuir model fitting. Temperature dependent kinetic study allowed determination of pseudo-second rate constant (10(3) g mg(-1) min(-1))/activation energies (kJ mol(-1)): 1.45/14.48 for diazinon, and 1.27/6.59 and 0.7/7.35 kJ mol(-1) for Cd2+ and Ni2+ ions, respectively. Thermodynamic parameters indicated feasible and spontaneous adsorption with main participation of physisorption. Antibacterial potential of npAg deposit for water disinfection was confirmed by the moderate reduction of bacterial growth of Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa, by 64%, 39%, and 70%, respectively. Thus, two synergistic effects contribute to water purification processes using Cy-npAg: pollutants removal with a simultaneous decrease of the microbial contamination contributing to overall water quality improvement.

The synthesis and adsorption potential of Cy-npAg, obtained by modification of raw montmorillonite clay (raw-Cy) with silver nanoparticle (npAg), was studied in this work. Optimization procedure, with respect to time, temperature and amount of deposit npAg, obtained either by reductive precipitation or ultraviolet irradiation, was performed using response surface methodology (RSM). The most efficient adsorbent, obtained by chemical reduction of silver ion with sodium borohydride, named Cy-npAg, was characterized in detail using Brunauer-Emmett-Teller, scanning electron microscopy, Fourier transform infrared spectroscopy and X-ray diffraction techniques, and point of zero charge determination. The Cy-npAg showed good adsorption capacity with respect to non-systemic organophosphate insecticide (diazinon) as well as of heavy metals ions (Cd2+ and Ni2+ ions), that is, 74.26, 62.33, and 35.49 mg g(-1), respectively, obtained from Langmuir model fitting. Temperature dependent kinetic study allowed determination of pseudo-second rate constant (10(3) g mg(-1) min(-1))/activation energies (kJ mol(-1)): 1.45/14.48 for diazinon, and 1.27/6.59 and 0.7/7.35 kJ mol(-1) for Cd2+ and Ni2+ ions, respectively. Thermodynamic parameters indicated feasible and spontaneous adsorption with main participation of physisorption. Antibacterial potential of npAg deposit for water disinfection was confirmed by the moderate reduction of bacterial growth of Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa, by 64%, 39%, and 70%, respectively. Thus, two synergistic effects contribute to water purification processes using Cy-npAg: pollutants removal with a simultaneous decrease of the microbial contamination contributing to overall water quality improvement.

In coatings technology, the possibility of introducing specific characteristics at the surface level allows for the manufacture of medical devices with efficient and prolonged antibacterial properties. This efficiency is often achieved by the use of a small amount of antibacterial molecules, which can fulfil their duty while limiting eventual releasing problems. The object of this work was the preparation and characterization of silver, titanium dioxide and chitosan polyurethane-based coatings. Coatings with the three antibacterials were prepared using different deposition techniques, using a brush or a bar coater automatic film applicator, and compared to solvent casted films prepared with the same components. For silver containing materials, an innovative strategy contemplating the use and preparation of silver nanoparticles in a single step-method was employed. This preparation was obtained starting from a silver precursor and using a single compound as the reducing agent and stabilizer. Ultraviolet-visible spectroscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy, contact angle measurements and adhesion test experiments were used to characterize the prepared coatings. Promising antibacterial properties, measured via direct and indirect methods, were registered for all the silver-based materials.

In this paper we have investigated and demonstrated the antimicrobial capabilities of nano-silver-4 wt%-kaolin (nAg-4-Kn) composite supported on borosilicate glass beads (BGB). Tests have been conducted in a fixed bed reactor on effluent from the secondary clarifier of a conventional wastewater treatment plant (WWTP) in Abu Dhabi, United Arab Emirates (UAE). The prepared BGB with immobilized nAg-4-Kn (nAg-4-Kn/BGB) were characterized using the RAMAN spectroscopy, TEM equipped with EDX and Focus Ion Beam Scanning Electron Microscope (FIB-SEM) techniques. The rate of disinfection was assessed through Luria-Bertani (LB)-agar plate cell counting technique. The results showed complete disinfection after few hours, which was preserved even after several days in repeated runs. The nAg-4-Kn/BGB was reused, demonstrating that the immobilization of nAg-4-Kn was stably achieved, and the activity and integrity of the composites on the BGB were preserved. First order disinfection kinetic constants were estimated to be 2.76 cm h−1 and 2.56 cm h−1 in two consecutive runs. Analyses of the beads after the experiments showed minor losses of nAg from the kaolin matrix thereby corroborating reusability of these materials.

The synthesis and adsorption potential of Cy-npAg, obtained by modification of raw montmorillonite clay (raw-Cy) with silver nanoparticle (npAg), was studied in this work. Optimization procedure, with respect to time, temperature and amount of deposit npAg, obtained either by reductive precipitation or ultraviolet irradiation, was performed using response surface methodology (RSM). The most efficient adsorbent, obtained by chemical reduction of silver ion with sodium borohydride, named Cy-npAg, was characterized in detail using Brunauer-Emmett-Teller, scanning electron microscopy, Fourier transform infrared spectroscopy and X-ray diffraction techniques, and point of zero charge determination. The Cy-npAg showed good adsorption capacity with respect to non-systemic organophosphate insecticide (diazinon) as well as of heavy metals ions (Cd2+ and Ni2+ ions), that is, 74.26, 62.33, and 35.49 mg g(-1), respectively, obtained from Langmuir model fitting. Temperature dependent kinetic study allowed determination of pseudo-second rate constant (10(3) g mg(-1) min(-1))/activation energies (kJ mol(-1)): 1.45/14.48 for diazinon, and 1.27/6.59 and 0.7/7.35 kJ mol(-1) for Cd2+ and Ni2+ ions, respectively. Thermodynamic parameters indicated feasible and spontaneous adsorption with main participation of physisorption. Antibacterial potential of npAg deposit for water disinfection was confirmed by the moderate reduction of bacterial growth of Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa, by 64%, 39%, and 70%, respectively. Thus, two synergistic effects contribute to water purification processes using Cy-npAg: pollutants removal with a simultaneous decrease of the microbial contamination contributing to overall water quality improvement.

Two main projects are described in this dissertation. In the first, high-nuclearity bismuth-nitrogen complexes were synthesized as potential precursors to nanomaterials. In the second, a one-pot, seedless approach of producing triangular silver nanoplates of controllable size was developed for light-harvesting applications.The synthesis of the bismuth-nitrogen cubane complex, [Bi4(NSnMe3)4Cl6]2−, from the reaction between [Bi2Cl9]3− and (Me3Sn)3N is presented. This is the first report of a bismuth-nitrogen cubane complex where the nitrogen sites of the Bi4N4 cube are solely bound to metal atoms. The reaction of [Bi4(NSnMe3)4Cl6]2− with GaCl3 produces [Bi4N4(GaCl3)4], which represents a rare transformation of a high-nuclearity compound directly to another through a metal exchange process. The reactions of [Bi4(NSnMe3)4Cl6]2− with other metal halides (AlCl3, InCl3, BiCl3, [Bi2Cl9]3−, and [GaCl4]1−) were also investigated, and the results suggest that similar transformations also occur. The technique of hot injection was then used with the complexes [Bi4(NSnMe3)4Cl6]2− and [Bi4N4(GaCl3)4] to explore whether they could serve as precursors to form bismuth-nitride containing nanoparticles. The resulting particles were characterized by scanning electron microscopy, which showed that the sizes were in fact in the micrometer range. The reactions to produce bismuth-nitrogen cubane complexes were adopted for synthesizing bismuth-phosphide complexes from [Bi2Cl9]3− and (Me3Si)3P.The final two chapters are devoted to the synthesis and application of silver nanoparticles. A new method of producing triangular silver nanoplates of tunable size is presented. These nanoplates can absorb or scatter light throughout the visible and infrared regions of light. Notably, these nanoplates are stable for long periods of time at room temperature and have capping agents that are easily displaced, which is important in potential applications. They can also be produced in large quantity. In prel

Two main projects are described in this dissertation. In the first, high-nuclearity bismuth-nitrogen complexes were synthesized as potential precursors to nanomaterials. In the second, a one-pot, seedless approach of producing triangular silver nanoplates of controllable size was developed for light-harvesting applications.The synthesis of the bismuth-nitrogen cubane complex, [Bi4(NSnMe3)4Cl6]2−, from the reaction between [Bi2Cl9]3− and (Me3Sn)3N is presented. This is the first report of a bismuth-nitrogen cubane complex where the nitrogen sites of the Bi4N4 cube are solely bound to metal atoms. The reaction of [Bi4(NSnMe3)4Cl6]2− with GaCl3 produces [Bi4N4(GaCl3)4], which represents a rare transformation of a high-nuclearity compound directly to another through a metal exchange process. The reactions of [Bi4(NSnMe3)4Cl6]2− with other metal halides (AlCl3, InCl3, BiCl3, [Bi2Cl9]3−, and [GaCl4]1−) were also investigated, and the results suggest that similar transformations also occur. The technique of hot injection was then used with the complexes [Bi4(NSnMe3)4Cl6]2− and [Bi4N4(GaCl3)4] to explore whether they could serve as precursors to form bismuth-nitride containing nanoparticles. The resulting particles were characterized by scanning electron microscopy, which showed that the sizes were in fact in the micrometer range. The reactions to produce bismuth-nitrogen cubane complexes were adopted for synthesizing bismuth-phosphide complexes from [Bi2Cl9]3− and (Me3Si)3P.The final two chapters are devoted to the synthesis and application of silver nanoparticles. A new method of producing triangular silver nanoplates of tunable size is presented. These nanoplates can absorb or scatter light throughout the visible and infrared regions of light. Notably, these nanoplates are stable for long periods of time at room temperature and have capping agents that are easily displaced, which is important in potential applications. They can also be produced in large quantity. In prel

Two main projects are described in this dissertation. In the first, high-nuclearity bismuth-nitrogen complexes were synthesized as potential precursors to nanomaterials. In the second, a one-pot, seedless approach of producing triangular silver nanoplates of controllable size was developed for light-harvesting applications.The synthesis of the bismuth-nitrogen cubane complex, [Bi4(NSnMe3)4Cl6]2−, from the reaction between [Bi2Cl9]3− and (Me3Sn)3N is presented. This is the first report of a bismuth-nitrogen cubane complex where the nitrogen sites of the Bi4N4 cube are solely bound to metal atoms. The reaction of [Bi4(NSnMe3)4Cl6]2− with GaCl3 produces [Bi4N4(GaCl3)4], which represents a rare transformation of a high-nuclearity compound directly to another through a metal exchange process. The reactions of [Bi4(NSnMe3)4Cl6]2− with other metal halides (AlCl3, InCl3, BiCl3, [Bi2Cl9]3−, and [GaCl4]1−) were also investigated, and the results suggest that similar transformations also occur. The technique of hot injection was then used with the complexes [Bi4(NSnMe3)4Cl6]2− and [Bi4N4(GaCl3)4] to explore whether they could serve as precursors to form bismuth-nitride containing nanoparticles. The resulting particles were characterized by scanning electron microscopy, which showed that the sizes were in fact in the micrometer range. The reactions to produce bismuth-nitrogen cubane complexes were adopted for synthesizing bismuth-phosphide complexes from [Bi2Cl9]3− and (Me3Si)3P.The final two chapters are devoted to the synthesis and application of silver nanoparticles. A new method of producing triangular silver nanoplates of tunable size is presented. These nanoplates can absorb or scatter light throughout the visible and infrared regions of light. Notably, these nanoplates are stable for long periods of time at room temperature and have capping agents that are easily displaced, which is important in potential applications. They can also be produced in large quantity. In prel

In the current study, we evaluated the modulatory effects of size and surface coating/charge of AgNPs on their toxicity to a unicellular yeast Saccharomyces cerevisiae BY4741–a fungal model. For that, the toxicity of a set of 10 and 80 nm citrate-coated (negatively charged) and branched polyethylenimine (bPEI) coated (positively charged) AgNPs was evaluated in parallel with AgNO3 as ionic control. Yeast cells were exposed to different concentrations of studied compounds in deionized water for 24 h at 30 °C and evaluated for the viability by the post-exposure colony-forming ability. Particle-cell interactions were assessed by SEM, TEM and confocal laser scanning microscopy (CLSM) in the reflection mode. AgNPs toxicity to yeast was size and charge-dependent: 24-h IC50 values ranged from 0.04 (10nAg-bPEI) up to 8.3 mg Ag/L (80nAg-Cit). 10 nm AgNPs were 5–27 times more toxic than 80 nm AgNPs and bPEI-AgNPs 8–44 times more toxic than citrate-AgNPs. SEM and TEM visualization showed that bPEI-AgNPs but not citrate-AgNPs adsorbed onto the yeast cell’s surface. However, according to CLSM all the studied AgNPs, whatever the size and coating, ended up within the yeast cell. Toxicity of citrate-AgNPs was largely explained by the dissolved Ag ions but the bPEI-AgNPs showed mainly particle-driven effects leading to the cellular internalization and/or to more pronounced dissolution of AgNPs in the close vicinity of the cell wall. Therefore, the size, and especially the coating/charge of AgNPs can be efficiently used for the design of new more efficient antifungals.

“This is a post-peer-review, pre-copyedit version of an article published in Cellulose. The final authenticated version is available online at: https://doi.org/10.1007/s10570-019-02678-5, Bacterial cellulose (BC) was functionalized applying the Laccase/TEMPO oxidative treatment, leading to a five-fold increase of the concentration of carboxyl groups. Paper produced with this cellulose showed improved mechanical properties while maintaining barrier function against water and greases as compared to paper produced with non-oxidized BC. Also, the negative charge provided by the carboxyl groups on functionalized BC was used to generate silver nanoparticles (AgNPs), obtaining a BC paper and Ag composite. The presence of AgNPs in the composites was validated by SEM, EDS and ICP analysis, showing spherical, uniformly sized particles stabilized in the BC nanofibers matrix. Additionally, antimicrobial property of composites containing AgNPs was tested. The results showed the strong antimicrobial activity of the composites against Gram-positive and Gram-negative bacteria and fungi. The generation of Ag nanoparticles in a matrix that combine the physical characteristics of the BC nanofibers with the stiffness and the mechanical properties of paper produced composites that may have applicability in technological and biomedical uses, Peer Reviewed, Postprint (author's final draft)

type:text, [ABSTRACT] Information concerning the unoccupied states of condensed matter is of great relevance to their electronic, optical and chemical properties. These unoccupied states can be directly examined by inverse photoelectron spectroscopy (IPES), which is often regarded as the time-inversion process of photoelectron spectroscopy (PES). The fundamental drawback of IPES is its low signal intensity. Other spectroscopic intensities are enhanced by surface plasmon resonance (SPR), so the intensity of the IPES signal may also be enhanced by SPR. This was, however, impossible because the photon energy involved in conventional IPES exceeds 9 eV and is much higher than the SPR energy of existing materials. In 2012, we developed low-energy IPES (LEIPS), in which the photon energy is less than 5 eV, which can then be matched with the SPR energy. We demonstrate a 5-fold enhancement of the LEIPS signal from a prototypical organic semiconductor, copper phthalocyanine (CuPc), by SPR of Ag nanoparticles.

Particularly-shaped silver nanostructures are successfully applied in many scientific fields, such as nanotechnology, catalysis, (nano)engineering, optoelectronics, and sensing. In recent years, the production of shape-controlled silver-based nanostructures and the knowledge around this topic has grown significantly. Hence, on the basis of the most recent results reported in the literature, a critical analysis around the driving forces behind the synthesis of such nanostructures are proposed herein, pointing out the important role of surface regulating agents in driving crystalline growth by favoring (or opposing) development along specific directions. Additionally, growth mechanisms of the different morphologies considered here are discussed in depth, and critical points highlighted

It is commonly true that a diluted colloidal suspension is more stable over time than a concentrated one because dilution reduces collision rates of the particles and therefore delays the formation of aggregates. However, this generalization does not apply for some engineered ligand-coated nanoparticles (NPs). We observed the opposite relationship between stability and concentration of NPs. We tested 4 different types of NPs: CdSe-11-mercaptoundecanoic acid, CdTe-polyelectrolytes, Ag-citrate, and Ag-polyvinylpyrrolidone. The results showed that dilution alone induced aggregation and subsequent sedimentation of the NPs that were originally monodispersed at very high concentrations. Increased dilution caused NPs to progressively become unstable in the suspensions. The extent of the dilution impact on the stability of NPs is different for different types of NPs. We hypothesize that the unavoidable decrease in free ligand concentration in the aqueous phase following dilution causes detachment of ligands from the suspended NP cores. The ligands attached to NP core surfaces must generally approach exchange equilibrium with free ligands in the aqueous phase; therefore, ligand detachment and destabilization are expected consequences of dilution. More studies are necessary to test this hypothesis. Because the stability of NPs determines their physicochemical and kinetic behavior including toxicity, dilution-induced instability needs to be understood to realistically predict the behavior of engineered ligand-coated NPs in aqueous systems. Environ Toxicol Chem 2018;37:1301-1308. © 2018 SETAC.

It is commonly true that a diluted colloidal suspension is more stable over time than a concentrated one because dilution reduces collision rates of the particles and therefore delays the formation of aggregates. However, this generalization does not apply for some engineered ligand-coated nanoparticles (NPs). We observed the opposite relationship between stability and concentration of NPs. We tested 4 different types of NPs: CdSe-11-mercaptoundecanoic acid, CdTe-polyelectrolytes, Ag-citrate, and Ag-polyvinylpyrrolidone. The results showed that dilution alone induced aggregation and subsequent sedimentation of the NPs that were originally monodispersed at very high concentrations. Increased dilution caused NPs to progressively become unstable in the suspensions. The extent of the dilution impact on the stability of NPs is different for different types of NPs. We hypothesize that the unavoidable decrease in free ligand concentration in the aqueous phase following dilution causes detachment of ligands from the suspended NP cores. The ligands attached to NP core surfaces must generally approach exchange equilibrium with free ligands in the aqueous phase; therefore, ligand detachment and destabilization are expected consequences of dilution. More studies are necessary to test this hypothesis. Because the stability of NPs determines their physicochemical and kinetic behavior including toxicity, dilution-induced instability needs to be understood to realistically predict the behavior of engineered ligand-coated NPs in aqueous systems. Environ Toxicol Chem 2018;37:1301-1308. © 2018 SETAC.

Background: Every medical graduate after completion of his course is posted in the emergency room where he/she faces many chest emergencies. In some chest emergencies a small intervention can be life-saving. In view of evidence based clinical practice every medical graduate should be confident to diagnose chest emergencies (e.g. Tension pneumothorax, massive pleural effusion, periodical effusion etc.) on radiographs, where an immediate intervention is necessary. Video Assisted learning (VAL) improves the performance of learners as it addresses a variety of learning styles. Video can be as good as an instructor in communicating facts or demonstrating procedures to assist in mastery learning where a student can view complex clinical or mechanical procedures as many times as they need to. In this study the advantages of video assisted learning would be used to enhance the academic output of learners. Method : 60 medical students of 6th semester were exposed to video assisted learning after traditional didactic lecture teaching on chest emergencies in the discipline of Radiology. Pretest OSCE was conducted in the form of interpretation of chest radiographs and post test OSCE was conducted after the intervention (VAL) Results: The average pretest score was 25.2 (31.5%) and average post test score was 48.15(60.18%). Based on the pretest scores, students were divided into three groups, i.e. Top one-third students, Middle one-third students and Bottom one-third students (i.e. slow learners). The pretest and post test results were compared as mean scores of the groups, with Paired t test. The difference in the scores was found to be statistically significant in all the groups (p value less than 0.001). The students perceived VAL as a good instructor which improves the understanding of complex case scenarios. Conclusion: Video assisted learning is an effective medium for teaching learning in graduate medical education.

Background: Every medical graduate after completion of his course is posted in the emergency room where he/she faces many chest emergencies. In some chest emergencies a small intervention can be life-saving. In view of evidence based clinical practice every medical graduate should be confident to diagnose chest emergencies (e.g. Tension pneumothorax, massive pleural effusion, periodical effusion etc.) on radiographs, where an immediate intervention is necessary. Video Assisted learning (VAL) improves the performance of learners as it addresses a variety of learning styles. Video can be as good as an instructor in communicating facts or demonstrating procedures to assist in mastery learning where a student can view complex clinical or mechanical procedures as many times as they need to. In this study the advantages of video assisted learning would be used to enhance the academic output of learners. Method : 60 medical students of 6th semester were exposed to video assisted learning after traditional didactic lecture teaching on chest emergencies in the discipline of Radiology. Pretest OSCE was conducted in the form of interpretation of chest radiographs and post test OSCE was conducted after the intervention (VAL) Results: The average pretest score was 25.2 (31.5%) and average post test score was 48.15(60.18%). Based on the pretest scores, students were divided into three groups, i.e. Top one-third students, Middle one-third students and Bottom one-third students (i.e. slow learners). The pretest and post test results were compared as mean scores of the groups, with Paired t test. The difference in the scores was found to be statistically significant in all the groups (p value less than 0.001). The students perceived VAL as a good instructor which improves the understanding of complex case scenarios. Conclusion: Video assisted learning is an effective medium for teaching learning in graduate medical education.

In this study, a chicken meat containing AgNPs (candidate reference material Nanolyse 14) has been used as a model matrix to study the fate and behaviour of AgNPs upon oral ingestion following an in vitro model that included saliva, gastric and intestinal digestions. The behaviour of a 40 nm AgNPs standard solution during the three digestion steps was also evaluated. Sample preparation conditions were optimised to prevent AgNPs oxidation and/or aggregation and to ensure the representativeness of the reported results. Total silver released from the test sample and the evaluated AgNP standard was determined by inductively coupled plasma mass spectrometry (ICPMS). The presence of both AgNPs and dissolved silver in the extracts was confirmed by single particle (SP)-ICPMS analysis. AgNPs were sized and the particle number concentration determined in the three digestion juices. Experimental results demonstrated differentiated behaviours for AgNP from the standard solution and the meat sample highlighting the relevance of using physiological conditions for accurate risk assessment. In the most realistic scenario assayed (i.e., spiked chicken meat analysis), only 13% of the AgNPs present in the reference material would reach the intestine wall. Meanwhile, other bioaccessible dissolved forms of silver would account for as much as 44% of the silver initially spiked to the meat paste., Ministerio de Economía y Competitividad (MINECO), Comunidad de Madrid, Depto. de Química Analítica, Fac. de Ciencias Químicas, TRUE, pub

The present study is focused on the synthesis and investigation of the physicochemical and biological properties of silver nanoparticles stabilized with a series of cationic gemini surfactants having a polymethylene spacer of variable length. UV-VIS spectroscopy, dynamic light scattering, scanning electron microscopy and zeta potential measurements were applied to provide physicochemical characterization of the silver nanoparticles. The mean size values of the nanoparticles were found to be in the 50 to 115 nm range. From the nanoparticle size distributions and scanning electron microscopy images it results that a population of small nanoparticles with the size of several nanometers was confirmed if the nanoparticles were stabilized with gemini molecules with either a short methylene spacer (two or four CH2 groups) or a long spacer (12 CH2 groups). The average zeta potential value for silver nanoparticles stabilized with gemini molecules is roughly independent of gemini surfactant spacer length and is approx. +58 mV. An interaction model between silver nanoparticles and gemini molecules which reflects the gained experimental data, is suggested. Microbicidal activity determinations revealed that the silver nanoparticles stabilized with gemini surfactants are more efficient against Gram-negative bacteria and yeasts, which has a direct relation to the interaction mechanism of nanoparticles with the bacterial cell membrane and its structural composition.

In this study, a chicken meat containing AgNPs (candidate reference material Nanolyse 14) has been used as a model matrix to study the fate and behaviour of AgNPs upon oral ingestion following an in vitro model that included saliva, gastric and intestinal digestions. The behaviour of a 40 nm AgNPs standard solution during the three digestion steps was also evaluated. Sample preparation conditions were optimised to prevent AgNPs oxidation and/or aggregation and to ensure the representativeness of the reported results. Total silver released from the test sample and the evaluated AgNP standard was determined by inductively coupled plasma mass spectrometry (ICPMS). The presence of both AgNPs and dissolved silver in the extracts was confirmed by single particle (SP)-ICPMS analysis. AgNPs were sized and the particle number concentration determined in the three digestion juices. Experimental results demonstrated differentiated behaviours for AgNP from the standard solution and the meat sample highlighting the relevance of using physiological conditions for accurate risk assessment. In the most realistic scenario assayed (i.e., spiked chicken meat analysis), only 13% of the AgNPs present in the reference material would reach the intestine wall. Meanwhile, other bioaccessible dissolved forms of silver would account for as much as 44% of the silver initially spiked to the meat paste., Ministerio de Economía y Competitividad (MINECO), Comunidad de Madrid, Depto. de Química Analítica, Fac. de Ciencias Químicas, TRUE, pub

In this study, a chicken meat containing AgNPs (candidate reference material Nanolyse 14) has been used as a model matrix to study the fate and behaviour of AgNPs upon oral ingestion following an in vitro model that included saliva, gastric and intestinal digestions. The behaviour of a 40 nm AgNPs standard solution during the three digestion steps was also evaluated. Sample preparation conditions were optimised to prevent AgNPs oxidation and/or aggregation and to ensure the representativeness of the reported results. Total silver released from the test sample and the evaluated AgNP standard was determined by inductively coupled plasma mass spectrometry (ICPMS). The presence of both AgNPs and dissolved silver in the extracts was confirmed by single particle (SP)-ICPMS analysis. AgNPs were sized and the particle number concentration determined in the three digestion juices. Experimental results demonstrated differentiated behaviours for AgNP from the standard solution and the meat sample highlighting the relevance of using physiological conditions for accurate risk assessment. In the most realistic scenario assayed (i.e., spiked chicken meat analysis), only 13% of the AgNPs present in the reference material would reach the intestine wall. Meanwhile, other bioaccessible dissolved forms of silver would account for as much as 44% of the silver initially spiked to the meat paste.

Background: The discovery of new solutions with antibacterial activity as efficient and safe alternatives to common preservatives (such as parabens) and to combat emerging infections and drug-resistant bacterial pathogens is highly expected in cosmetics and pharmaceutics. Colloidal silver nanoparticles (NPs) are attracting interest as novel effective antimicrobial agents for the prevention of several infectious diseases. Methods: Water-soluble, negatively charged silver nanoparticles (AgNPs) were synthesized by reduction with citric and tannic acid and characterized by transmission electron microscopy, dynamic light scattering, zeta potential, differential centrifuge sedimentation, and ultraviolet–visible spectroscopy. AgNPs were tested with model Gram-negative and Gram-positive bacteria in comparison to two different kinds of commercially available AgNPs. Results: In this work, AgNPs with higher antibacterial activity compared to the commercially available colloidal silver solutions were prepared and investigated. Bacteria were plated and the antibacterial activity was tested at the same concentration of silver ions in all samples. The AgNPs did not show any significant reduction in the antibacterial activity for an acceptable time period. In addition, AgNPs were transferred to organic phase and retained their antibacterial efficacy in both aqueous and nonaqueous media and exhibited no toxicity in eukaryotic cells. Conclusion: We developed AgNPs with a 20 nm diameter and negative zeta potential with powerful antibacterial activity and low toxicity compared to currently available colloidal silver, suitable for cosmetic preservatives and pharmaceutical preparations administrable to humans and/or animals as needed.

The present study is focused on the synthesis and investigation of the physicochemical and biological properties of silver nanoparticles stabilized with a series of cationic gemini surfactants having a polymethylene spacer of variable length. UV-VIS spectroscopy, dynamic light scattering, scanning electron microscopy and zeta potential measurements were applied to provide physicochemical characterization of the silver nanoparticles. The mean size values of the nanoparticles were found to be in the 50 to 115 nm range. From the nanoparticle size distributions and scanning electron microscopy images it results that a population of small nanoparticles with the size of several nanometers was confirmed if the nanoparticles were stabilized with gemini molecules with either a short methylene spacer (two or four CH2 groups) or a long spacer (12 CH2 groups). The average zeta potential value for silver nanoparticles stabilized with gemini molecules is roughly independent of gemini surfactant spacer length and is approx. +58 mV. An interaction model between silver nanoparticles and gemini molecules which reflects the gained experimental data, is suggested. Microbicidal activity determinations revealed that the silver nanoparticles stabilized with gemini surfactants are more efficient against Gram-negative bacteria and yeasts, which has a direct relation to the interaction mechanism of nanoparticles with the bacterial cell membrane and its structural composition.

The present study is focused on the synthesis and investigation of the physicochemical and biological properties of silver nanoparticles stabilized with a series of cationic gemini surfactants having a polymethylene spacer of variable length. UV-VIS spectroscopy, dynamic light scattering, scanning electron microscopy and zeta potential measurements were applied to provide physicochemical characterization of the silver nanoparticles. The mean size values of the nanoparticles were found to be in the 50 to 115 nm range. From the nanoparticle size distributions and scanning electron microscopy images it results that a population of small nanoparticles with the size of several nanometers was confirmed if the nanoparticles were stabilized with gemini molecules with either a short methylene spacer (two or four CH2 groups) or a long spacer (12 CH2 groups). The average zeta potential value for silver nanoparticles stabilized with gemini molecules is roughly independent of gemini surfactant spacer length and is approx. +58 mV. An interaction model between silver nanoparticles and gemini molecules which reflects the gained experimental data, is suggested. Microbicidal activity determinations revealed that the silver nanoparticles stabilized with gemini surfactants are more efficient against Gram-negative bacteria and yeasts, which has a direct relation to the interaction mechanism of nanoparticles with the bacterial cell membrane and its structural composition.

The present study is focused on the synthesis and investigation of the physicochemical and biological properties of silver nanoparticles stabilized with a series of cationic gemini surfactants having a polymethylene spacer of variable length. UV-VIS spectroscopy, dynamic light scattering, scanning electron microscopy and zeta potential measurements were applied to provide physicochemical characterization of the silver nanoparticles. The mean size values of the nanoparticles were found to be in the 50 to 115 nm range. From the nanoparticle size distributions and scanning electron microscopy images it results that a population of small nanoparticles with the size of several nanometers was confirmed if the nanoparticles were stabilized with gemini molecules with either a short methylene spacer (two or four CH2 groups) or a long spacer (12 CH2 groups). The average zeta potential value for silver nanoparticles stabilized with gemini molecules is roughly independent of gemini surfactant spacer length and is approx. +58 mV. An interaction model between silver nanoparticles and gemini molecules which reflects the gained experimental data, is suggested. Microbicidal activity determinations revealed that the silver nanoparticles stabilized with gemini surfactants are more efficient against Gram-negative bacteria and yeasts, which has a direct relation to the interaction mechanism of nanoparticles with the bacterial cell membrane and its structural composition.

The present study is focused on the synthesis and investigation of the physicochemical and biological properties of silver nanoparticles stabilized with a series of cationic gemini surfactants having a polymethylene spacer of variable length. UV-VIS spectroscopy, dynamic light scattering, scanning electron microscopy and zeta potential measurements were applied to provide physicochemical characterization of the silver nanoparticles. The mean size values of the nanoparticles were found to be in the 50 to 115 nm range. From the nanoparticle size distributions and scanning electron microscopy images it results that a population of small nanoparticles with the size of several nanometers was confirmed if the nanoparticles were stabilized with gemini molecules with either a short methylene spacer (two or four CH2 groups) or a long spacer (12 CH2 groups). The average zeta potential value for silver nanoparticles stabilized with gemini molecules is roughly independent of gemini surfactant spacer length and is approx. +58 mV. An interaction model between silver nanoparticles and gemini molecules which reflects the gained experimental data, is suggested. Microbicidal activity determinations revealed that the silver nanoparticles stabilized with gemini surfactants are more efficient against Gram-negative bacteria and yeasts, which has a direct relation to the interaction mechanism of nanoparticles with the bacterial cell membrane and its structural composition.

This paper reports rapid and eco-friendly biosynthesis of silver nanoparticles using latex of two different plants Jatropha curcas (Jc) and Lannea grandis (Lg). Latex of these plants act as both reducing as well as capping agent. The surface plasmon resonance (SPR) band of as-synthesized silver nanocolloids (AgNC) appeared at 440 nm and 415 nm for the AgNC synthesized by latex of Jc and Lg, respectively. TEM images show that the latex of Lg produced smaller regular-shaped particles than those produced by latex of Jc. The influence of different synthesis parameters like concentration of latex, concentration of metal ion, time of reaction etc., on the morphology of the particles were also studied by monitoring UV-Vis spectra of the samples.

Background: The discovery of new solutions with antibacterial activity as efficient and safe alternatives to common preservatives (such as parabens) and to combat emerging infections and drug-resistant bacterial pathogens is highly expected in cosmetics and pharmaceutics. Colloidal silver nanoparticles (NPs) are attracting interest as novel effective antimicrobial agents for the prevention of several infectious diseases. Methods: Water-soluble, negatively charged silver nanoparticles (AgNPs) were synthesized by reduction with citric and tannic acid and characterized by transmission electron microscopy, dynamic light scattering, zeta potential, differential centrifuge sedimentation, and ultraviolet–visible spectroscopy. AgNPs were tested with model Gram-negative and Gram-positive bacteria in comparison to two different kinds of commercially available AgNPs. Results: In this work, AgNPs with higher antibacterial activity compared to the commercially available colloidal silver solutions were prepared and investigated. Bacteria were plated and the antibacterial activity was tested at the same concentration of silver ions in all samples. The AgNPs did not show any significant reduction in the antibacterial activity for an acceptable time period. In addition, AgNPs were transferred to organic phase and retained their antibacterial efficacy in both aqueous and nonaqueous media and exhibited no toxicity in eukaryotic cells. Conclusion: We developed AgNPs with a 20 nm diameter and negative zeta potential with powerful antibacterial activity and low toxicity compared to currently available colloidal silver, suitable for cosmetic preservatives and pharmaceutical preparations administrable to humans and/or animals as needed.

This paper reports rapid and eco-friendly biosynthesis of silver nanoparticles using latex of two different plants Jatropha curcas (Jc) and Lannea grandis (Lg). Latex of these plants act as both reducing as well as capping agent. The surface plasmon resonance (SPR) band of as-synthesized silver nanocolloids (AgNC) appeared at 440 nm and 415 nm for the AgNC synthesized by latex of Jc and Lg, respectively. TEM images show that the latex of Lg produced smaller regular-shaped particles than those produced by latex of Jc. The influence of different synthesis parameters like concentration of latex, concentration of metal ion, time of reaction etc., on the morphology of the particles were also studied by monitoring UV-Vis spectra of the samples.

Silver nanoparticles (AgNPs) are among the most exploited antimicrobial agents and are used in many consumer products. Size and surface reactivity are critical physico-chemical properties responsible for NPs toxicity, and surface coatings, often used to functionalize or stabilize AgNPs, can influence their toxic profile and biocompatibility. In the current study the developmental toxicity of (1) negatively charged citrate-coated AgNPs (Cit-AgNPs), (2) positively charged branched polyethylenimine-coated AgNPs (BPEIAgNPs), and (3) Agþ (from 0.0625 to 0.75 mg Ag/L) was investigated by the standard Frog Embryo Teratogenesis Assay – Xenopus (FETAX). In order to identify the most sensitive developmental phase, embryos were also exposed during different embryonic stages. Morphological and bio-physical studies were performed to characterize tissue lesions and NP uptake. The results suggest that Agþ was strongly embryo-lethal. Contrary to Cit-AgNPs, the positively charged BPEI-AgNPs exert a concentration-dependent effect on lethality and malformations of embryos. The BPEI-AgNPs showed the highest teratogenic index (TI1⁄4 1.6), pointing out the role of functional coating in determining the developmental hazard. The highest susceptibility to BPEI-AgNPs was during early embryogenesis, when embryos are still enclosed in the fertilization envelope, and the post-stomodeum opening stages, when NPs ingestion occurs. In BPEIAgNPs treated larvae, the histological examination revealed irregular intestinal diverticula coupled with edematous connective tissue. Small NPs aggregates are mapped throughout the intestinal mucosa and secondary target organs by two-photon excitation microscopy. We conclude that a teratogenic risk may be associated with BPEI-AgNPs exposure, but the modality of NP-tissue interactions and the teratogenic mechanism need further investigations to be better defined.

In this study, a chicken meat containing AgNPs (candidate reference material Nanolyse 14) has been used as a model matrix to study the fate and behaviour of AgNPs upon oral ingestion following an in vitro model that included saliva, gastric and intestinal digestions. The behaviour of a 40 nm AgNPs standard solution during the three digestion steps was also evaluated. Sample preparation conditions were optimised to prevent AgNPs oxidation and/or aggregation and to ensure the representativeness of the reported results. Total silver released from the test sample and the evaluated AgNP standard was determined by inductively coupled plasma mass spectrometry (ICPMS). The presence of both AgNPs and dissolved silver in the extracts was confirmed by single particle (SP)-ICPMS analysis. AgNPs were sized and the particle number concentration determined in the three digestion juices. Experimental results demonstrated differentiated behaviours for AgNP from the standard solution and the meat sample highlighting the relevance of using physiological conditions for accurate risk assessment. In the most realistic scenario assayed (i.e., spiked chicken meat analysis), only 13% of the AgNPs present in the reference material would reach the intestine wall. Meanwhile, other bioaccessible dissolved forms of silver would account for as much as 44% of the silver initially spiked to the meat paste.

Single-particle inductively coupled plasma mass spectrometry (sp-ICP-MS) promises fast and selective determination of nanoparticle size and number concentrations. While several studies on practical applications have been published, data on formal, especially interlaboratory validation of sp-ICP-MS, is sparse. An international interlaboratory study was organized to determine repeatability and reproducibility of the determination of the median particle size and particle number concentration of Ag nanoparticles (AgNPs) in chicken meat. Ten laboratories from the European Union, the USA, and Canada determined particle size and particle number concentration of two chicken meat homogenates spiked with polyvinylpyrrolidone (PVP)-stabilized AgNPs. For the determination of the median particle diameter, repeatability standard deviations of 2 and 5% were determined, and reproducibility standard deviations were 15 and 25%, respectively. The equivalent median diameter itself was approximately 60% larger than the diameter of the particles in the spiking solution. Determination of the particle number concentration was significantly less precise, with repeatability standard deviations of 7 and 18% and reproducibility standard deviations of 70 and 90%.

A comparative study of the reduction of aqueous silver (Ag) and gold (Au) salts to colloidal Ag and Au nanoparticles, respectively, by a gaseous, cathodic, atmospheric-pressure microplasma electrode is presented. The resulting nanoparticles (NPs) were characterized by ultraviolet-visible (UV-vis) absorption spectroscopy and transmission electron microscopy (TEM), and the aqueous solution composition before and after experiments was determined by ionic conductivity, electrochemical potential, and/or UV-vis absorption measurements. TEM showed that Ag and Au NPs were spherical and non-agglomerated when synthesized in the presence of a stabilizer, polyvinyl alcohol. The charge injected by the plasma was correlated to the maximum intensity in the absorbance spectra which in turn depends on the nanoparticle concentration. Separately, the charge injected was correlated to the metal cation concentration. Ag and Au reduction rates were found to be directly proportional to the charge injected, independent of plasma current and process time. Differences in the mechanism for Ag and Au reduction were also observed, and solution species generated by the plasma and their role in the reduction process (e.g. H2O2, electrons) is discussed., SCOPUS: ar.j, info:eu-repo/semantics/published

Single-particle inductively coupled plasma mass spectrometry (sp-ICP-MS) promises fast and selective determination of nanoparticle size and number concentrations. While several studies on practical applications have been published, data on formal, especially interlaboratory validation of sp-ICP-MS, is sparse. An international interlaboratory study was organized to determine repeatability and reproducibility of the determination of the median particle size and particle number concentration of Ag nanoparticles (AgNPs) in chicken meat. Ten laboratories from the European Union, the USA, and Canada determined particle size and particle number concentration of two chicken meat homogenates spiked with polyvinylpyrrolidone (PVP)-stabilized AgNPs. For the determination of the median particle diameter, repeatability standard deviations of 2 and 5% were determined, and reproducibility standard deviations were 15 and 25%, respectively. The equivalent median diameter itself was approximately 60% larger than the diameter of the particles in the spiking solution. Determination of the particle number concentration was significantly less precise, with repeatability standard deviations of 7 and 18% and reproducibility standard deviations of 70 and 90%.