Peculiarities of synthesis and bactericidal properties of nanosilver in colloidal solutions, SiO2 films and in the textile structure: a review

The aim of this work is a comparative analysis of the biocidal efficiency of Ag nanoparticles (NPs) in the colloidal state, in the structure of films and dispersions of SiO2 and in the composition of textile fabrics, dependent on the method of synthesis, based on literature data and on own researches. Chemical reduction of silver (with borohydrides, hydrogen, hydrazine, etc.) allows one to adjust and control the size and shape of NPs. The shape of the NPs is mostly spherical, what is confirmed by the presence of a band of surface plasmon resonance in absorption spectra and by electron microscopy measurements. To prevent aggregation of NPs obtained by the method of chemical reduction in solution, the optimal ratio of two stabilizers based on surfactants and polymer at their minimum concentration was found, namely NaBH4 as a reductant and polyvinylpyrrolidone + sodium dodecyl sulfate as binary stabilizer of Ag NPs, with bactericidal activity of 99 % and stability for more than 3 years. Chemical reduction of silver ions was carried out also by the amino acid tryptophan (Trp) which has a dual function – a biocompatible reducing agent and stabilizer of silver NPs while maintaining their shape, size and stability for long-term use. Effective methods of photochemical synthesis of Ag NPs have been developed in different ways: by UV irradiation of Ag+ ions in solution in the presence of solid-state photosensitizer SiO2 with adsorbed benzophenone (SiO2/BPh); by UV irradiation of Ag+ ions in solution in the presence of the amino acid tryptophan (Trp); on silica surface when Ag/SiO2 sol-gel films production via irradiation of adsorbed Ag+ ions on SiO2 film (Ag+/SiO2) in the BPh solution. It is shown that when Ag NPs are adsorbed on the surface of highly dispersed SiO2, the logarithm of the reduction of microorganisms reduces and the time of their deactivation increases. A cheap and convenient way to modify of cotton textiles with Ag NPs by soft heat treatment of Ag+/cotton samples with high (90–95 %) efficiency of destruction of bacteria E. coli, K. pneumoniae, E. aerogenes, P. vulgaris, S. aureus, C. albicans, etc., with saving of biocidal activity after 5 cycles of washing has been developed. The dynamics of silver ions release from the surface of NPs in the structure of textile upon their contact with water for 72 hours and the number of irreversibly bound particles have been studied. The electrical resistance of the tissue is proportional to the quantity of NPs. That is NPs in the structure are in different degrees of binding, a certain part of them is retained (adsorbed) irreversibly, saving bactericidal properties after repeated contacts with water. On the basis of literature analysis it is shown that ecologically safe “green synthesis” is a promising way to silver NPs produce with pronounced bactericidal efficiency, which is becoming more common due to the large resource of cheap plant raw materials.

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Fabrication of TiO2/Ag/Ag2O Nanoparticles to Enhance the Photocatalytic Activity of Degussa P25 Titania

Australian Journal of Chemistry ◽

10.1071/ch15250 ◽

2016 ◽

Vol 69 (1) ◽

pp. 41 ◽

Cited By ~ 11

Author(s):

Safyan A. Khan ◽

Shahid Ali ◽

Manzar Sohail ◽

Mohamed A. Morsy ◽

Zain H. Yamani

Keyword(s):

Chemical Reduction ◽

Visible Region ◽

Spherical Shape ◽

Ag Nps ◽

X Ray ◽

Transmission Electron ◽

Silver Nps ◽

Degussa P25 ◽

Average Size ◽

Ag2o Nanoparticles

A simple chemical reduction approach was used to synthesize Ag nanoparticles (NPs) over a reputed photocatalyst, Degussa P25 (TiO2). Silver doping extended the P25 absorption wavelength from the ultraviolet to the visible region. The synthesized silver NPs (Ag NPs) were of spherical shape and had an average size of ~4.6 nm. In the next stage, Ag NPs were partially oxidized by treatment with hydrogen peroxide. The resulting P25/Ag/Ag2O nanocomposites were characterized by X-ray powder diffraction, transmission electron microscopy, energy dispersive X-ray analysis, Brunauer–Emmett–Teller analysis, and UV-visible spectroscopy. The photocatalytic activities of the P25, P25/Ag, and P25/Ag/Ag2O catalysts were investigated for the degradation of non-biodegradable dyes, methylene blue and rhodamine 6G. The P25/Ag/Ag2O nanocomposite exhibited better photodegradation activity than P25, as well as the commonly used Ag3PO4, under visible light irradiation.

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Dietary intake of tryptophan tied emotion-related impulsivity in humans

International Journal for Vitamin and Nutrition Research ◽

10.1024/0300-9831/a000608 ◽

2019 ◽

pp. 1-8 ◽

Cited By ~ 1

Author(s):

Florian Javelle ◽

Descartes Li ◽

Philipp Zimmer ◽

Sheri L. Johnson

Keyword(s):

Amino Acids ◽

Amino Acid ◽

Food Intake ◽

Essential Amino Acid ◽

Food Habits ◽

Psychological Disorder ◽

Serotonin Synthesis ◽

Amino Acid Tryptophan ◽

Pass Through ◽

Three Factor

Abstract. Emotion-related impulsivity, defined as the tendency to say or do things that one later regret during periods of heightened emotion, has been tied to a broad range of psychopathologies. Previous work has suggested that emotion-related impulsivity is tied to an impaired function of the serotonergic system. Central serotonin synthesis relies on the intake of the essential amino acid, tryptophan and its ability to pass through the blood brain barrier. Objective: The aim of this study was to determine the association between emotion-related impulsivity and tryptophan intake. Methods: Undergraduate participants (N = 25, 16 women, 9 men) completed a self-rated measure of impulsivity (Three Factor Impulsivity Index, TFI) and daily logs of their food intake and exercise. These data were coded using the software NutriNote to evaluate intakes of tryptophan, large neutral amino acids, vitamins B6/B12, and exercise. Results: Correlational analyses indicated that higher tryptophan intake was associated with significantly lower scores on two out of three subscales of the TFI, Pervasive Influence of Feelings scores r = –.502, p < . 010, and (lack-of) Follow-Through scores, r = –.407, p < . 050. Conclusion: Findings provide further evidence that emotion-related impulsivity is correlated to serotonergic indices, even when considering only food habits. It also suggests the need for more research on whether tryptophan supplements might be beneficial for impulsive persons suffering from a psychological disorder.

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Antibacterial Effect of Amino Acid–Silver Complex Loaded Montmorillonite Incorporated in Dental Acrylic Resin

Materials ◽

10.3390/ma14061442 ◽

2021 ◽

Vol 14 (6) ◽

pp. 1442

Author(s):

Kumiko Yoshihara ◽

Noriyuki Nagaoka ◽

Aya Umeno ◽

Akinari Sonoda ◽

Hideki Obika ◽

...

Keyword(s):

Amino Acid ◽

Antibacterial Agents ◽

Antibacterial Effect ◽

Dental Materials ◽

Silver Ions ◽

Acrylic Resin ◽

Chloride Ions ◽

Antibacterial Efficacy ◽

Growth Measurement ◽

Dental Acrylic

Several dental materials contain silver for antibacterial effect, however the effect is relatively low. The reason for the lower antibacterial efficacy of silver is considered to be the fact that silver ions bind to chloride ions in saliva. To develop new effective silver antibacterial agents that can be useful in the mouth, we synthesized two novel amino acid (methionine or histidine)–silver complexes (Met or His–Ag) loaded with montmorillonite (Mont) and analyzed their antibacterial efficacy. At first the complexes were characterized using nuclear magnetic resonance (NMR), and amino acid–Ag complex-loaded Mont (amino acid–Ag–Mont) were characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The antibacterial efficacy of these materials in dental acrylic resin was then investigated by bacterial growth measurement using a spectrophotometer. As controls, commercially available silver-loaded zeolite and silver-zirconium phosphate were also tested. Dental acrylic resin incorporating His–Ag–Mont strongly inhibited Streptococcus mutans growth. This was explained by the fact that His-Ag complex revealed the highest amounts of silver ions in the presence of chloride. The structure of the amino acid–Ag complexes affected the silver ion presence in chloride and the antibacterial efficacy. His–Ag–Mont might be used as antibacterial agents for dental materials.

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Size Control of Synthesized Silver Nanoparticles by Simultaneous Chemical Reduction and Laser Fragmentation in Origanum majorana Extract: Antibacterial Application

Materials ◽

10.3390/ma14092326 ◽

2021 ◽

Vol 14 (9) ◽

pp. 2326

Author(s):

Entesar Ali Ganash ◽

Reem Mohammad Altuwirqi

Keyword(s):

Silver Nanoparticles ◽

Irradiation Time ◽

Chemical Reduction ◽

Size Control ◽

Reduction Process ◽

Laser Wavelength ◽

X Ray Diffraction ◽

Ag Nps ◽

Transmission Electron ◽

Origanum Majorana

In this work, silver nanoparticles (Ag NPs) were synthesized using a chemical reduction approach and a pulsed laser fragmentation in liquid (PLFL) technique, simultaneously. A laser wavelength of 532 nm was focused on the as produced Ag NPs, suspended in an Origanum majorana extract solution, with the aim of controlling their size. The effect of liquid medium concentration and irradiation time on the properties of the fabricated NPs was studied. While the X-ray diffraction (XRD) pattern confirmed the existence of Ag NPs, the UV–Vis spectrophotometry showed a significant absorption peak at about 420 nm, which is attributed to the characteristic surface plasmon resonance (SPR) peak of the obtained Ag NPs. By increasing the irradiation time and the Origanum majora extract concentration, the SPR peak shifted toward a shorter wavelength. This shift indicates a reduction in the NPs’ size. The effect of PLFL on size reduction was clearly revealed from the transmission electron microscopy images. The PLFL technique, depending on experimental parameters, reduced the size of the obtained Ag NPs to less than 10 nm. The mean zeta potential of the fabricated Ag NPs was found to be greater than −30 mV, signifying their stability. The Ag NPs were also found to effectively inhibit bacterial activity. The PLFL technique has proved to be a powerful method for controlling the size of NPs when it is simultaneously associated with a chemical reduction process.

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Highly specific “sensing” of tryptophan by a luminescent europium(III) complex

Zeitschrift für Naturforschung B ◽

10.1515/znb-2016-0096 ◽

2016 ◽

Vol 71 (10) ◽

pp. 1025-1028 ◽

Cited By ~ 1

Author(s):

Jan A. Stubenrauch ◽

Christian Mevissen ◽

Marie F. Schulte ◽

Steffen Bochenek ◽

Markus Albrecht ◽

...

Keyword(s):

Amino Acid ◽

Europium Complex ◽

Phenanthroline Ligand ◽

Amino Acid Tryptophan ◽

Tryptophan Emission

AbstractThe europium(III) complex 1-Cl3 (S,S-2,2′-(((1,10-phenanthroline-2,9-diyl)bis(methanylylidene))bis(azanylylidene))bis(3-methylbutanamide)europiumtrichloride) undergoes, only in the presence of the amino acid tryptophan, a change of emission at 615 nm. In the presence of few equivalents of tryptophan, emission of the europium complex is enhanced while it disappears upon addition of large amounts. This behavior can be assigned to displacement of the sensitizing phenanthroline ligand of 1-Cl2•Trp in the latter case.

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Effect of UV irradiation on cell surface protease activity and amino acid uptake

Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis ◽

10.1016/s0027-5107(98)00175-4 ◽

1998 ◽

Vol 422 (1) ◽

pp. 55-67 ◽

Cited By ~ 6

Author(s):

Terrence J. Piva ◽

Kari G. Francis ◽

Darren R. Krause ◽

Grace M. Chojnowski ◽

Kay A.O. Ellem

Keyword(s):

Amino Acid ◽

Cell Surface ◽

Uv Irradiation ◽

Protease Activity ◽

Amino Acid Uptake ◽

Acid Uptake ◽

Cell Surface Protease

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Green Synthesis of Silver Nanoparticles Using Raw Fruit Extract of Mimusops elengi and their Antimicrobial Study

Biointerface Research in Applied Chemistry ◽

10.33263/briac113.1004010051 ◽

2020 ◽

Vol 11 (3) ◽

pp. 10040-10051

Keyword(s):

Green Synthesis ◽

Colloidal Stability ◽

Low Cost ◽

Antimicrobial Activities ◽

Health Food ◽

Ag Nps ◽

Fruit Extract ◽

Silver Nps ◽

Mimusops Elengi ◽

Bacteria And Fungi

These days, nanoparticles are being considered as nano-antibiotics because of their execution of antimicrobial activities towards a broad range of microbes. Nanoparticles are used in industrial products, health, food, space, and cosmetics;thus, researchers need for a green, ecofriendly, and low-cost approach to synthesize it. Green synthesis is such an approach of synthesizing NPs using microorganisms and plants, which is free of additional impurities. We used Mimusops elengi Linn. raw fruit extract in water to reduce the silver nitrate salt to produce silver NPs. The samples were characterized using various instrumental techniques. Broadband known as Surface Plasmon Resonance found near 450 nm in the absorption spectrum shows the formation of Ag NPs. NPs with average hydrodynamic diameters in the ranges 20-300 nm were detected from DLS study having negative zeta potential value (varies between - 25.8 to 15.8 mV), which suggests that as NPs surface is charged, it provides colloidal stability to the NPs in a liquid medium. FTIR study reveals that an increase in the intensity of some of the vibrational band with NP-content is due to the adsorption of some molecules on the surface of NPs. XRD pattern shows that NPs have an fcc structure. Samples were tested to have capabilities to kill both bacteria and fungi.

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Silver nanoparticles used to counter Monilinia fructicola fungicide-resistance and reduce fungicide environmental footprint

10.5194/egusphere-egu21-9285 ◽

2021 ◽

Author(s):

Constantinos Chrysikopoulos ◽

Anastasios A. Malandrakis ◽

Nektarios Kavroulakis ◽

Anthi Stefanarou

Keyword(s):

Silver Nanoparticles ◽

Control Plant ◽

Resistance Mutation ◽

Silver Ions ◽

Apple Fruit ◽

Ag Nps ◽

Gene Target ◽

Benzimidazole Fungicides

<div>The potential of silver nanoparticles (Ag-NPs) to control plant pathogen Moniliafructicola and to deter environmental contamination by reducing fungicide doses was evaluated in vitro and in vivo. &#160;Fungitoxicity screening of&#160;M. fructicola&#160;isolates resulted in the detection of 18 benzimidazole-resistant (BEN-R) isolates with reduced sensitivity to fungicides &#160;thiophanate methyl (TM)&#160; and carbendazim. All resistant isolates caried the E198A resistance mutation in their &#946;-tubulin gene, target site of the benzimidazole fungicides.&#160;Ag-NPs could effectively control both sensitive (BEN-S) and resistant isolates while the combination of Ag-NPs with TM significantly enhanced their fungitoxic effect both in vitro&#160;and in apple fruit tests. The positive correlation observed between Ag-NPs and TM+Ag-NPs treatments indicates a mixture-enhanced Ag-NPs activity/availability as a possible mechanism of synergy. No correlation between Ag-NPs&#160; and AgNO3&#160;could&#160; be found suggesting difference(s) in the fungitoxic mechanism of action between Nps and their bulk/ionic counterparts. Indications of the involvement of energy (ATP) metabolism in the mode of action of Ag-NPs were also evident by the synergy observed between Ag-NPs and the oxidative phosphorylation-uncoupler fluazinam (FM) against both BEN-R and BEN-S phenotypes. The role of silver ions release on the inhibitory action of Ag-NPs against the fungusis probably limited since the AgNPs/NaCl combination enhanced fungitoxicity, a fact that could not be justified by the expected binding of silver with chlorine ions. Concluding, Ag-NPs can be effectively used as a means of controlling both BEN-S and BEN-R M.&#160;fructicola&#160;isolates while&#160;their combination with conventional fungicides should aid anti-resistant strategies and reduce the environmental impact of synthetic fungicides by reducing effective doses to the control the pathogen.</div>

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