Marine Bacterial Exopolymers-Mediated Green Synthesis of Noble Metal Nanoparticles with Antimicrobial Properties

A straightforward and green method for the synthesis of gold, silver, and silver chloride nanoparticles (Au NPs and Ag/AgCl NPs) was developed using three different microbial exopolymers (EP) as reducing and stabilizing agents. The exopolysaccharides EPS B3-15 and EPS T14 and the poly-γ-glutamic acid γ-PGA-APA were produced by thermophilic bacteria isolated from shallow hydrothermal vents off the Eolian Islands (Italy) in the Mediterranean Sea. The production of metal NPs was monitored by UV−Vis measurements by the typical plasmon resonance absorption peak and their antimicrobial activity towards Gram-positive and Gram- negative bacteria (Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa), as well as fungi (Candida albicans) was investigated. The biological evaluation showed no activity for EP-Au NPs, except against E. coli, whereas EP-Ag NPs exhibited a broad-spectrum of activity. The chemical composition, morphology, and size of EP-Ag NPs were investigated by UV–Vis, zeta potential (ζ), dynamic light scattering (DLS) measurements and transmission electron microscopy (TEM). The best antimicrobial results were obtained for EPS B3-15-Ag NPs and EPS T14-Ag NPs (Minimum Inhibitory Concentration, MIC: 9.37–45 µg/mL; Minimum Bactericidal Concentration/Minimum Fungicidal Concentration, MBC/MFC: 11.25–75 µg/mL).

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Green approach in gold, silver and selenium nanoparticles using coffee bean extract

Open Agriculture ◽

10.1515/opag-2020-0074 ◽

2020 ◽

Vol 5 (1) ◽

pp. 761-767

Author(s):

Reiyhaneh Abbasian ◽

Hoda Jafarizadeh-Malmiri

Keyword(s):

Spherical Shape ◽

Coffee Bean ◽

Hydrothermal Conditions ◽

Ag Nps ◽

Au Nps ◽

Stabilizing Agents ◽

E Coli ◽

Green Approach ◽

Gold Silver ◽

Ft Ir

AbstractGreen fabrication of metal nanoparticles (NPs), using natural reducing and stabilizing agents existed in plants and their derivatives, due to their unique properties, has gained more attention. The present study focuses on the synthesis of gold (Au), silver (Ag) and selenium (Se) NPs using coffee bean extract under hydrothermal conditions (1.5 atm and 121°C, for 15 min). Coffee bean extract obtained in 2 h processing using Clevenger apparatus and Fourier transform-infrared (FT-IR) spectroscopy indicated five highlighted peaks, namely, hydroxyl, amide, aromatic, alkane and ring groups. Dynamic light scattering analysis revealed that among three different NPs formed, fabricated Ag NPs had small particle size (153 nm) and high zeta potential value (16.8 mV). However, synthesized Au NPs had minimum polydispersity index (0.312). Results also indicated that fabricated Au, Se and Ag NPs had low antioxidant activity with values of 9.1, 8.9 and 8.7%, respectively. Morphological and antibacterial activity assessments, demonstrated that synthesized Ag, Au and Se NPs had spherical shape and high bactericidal activity against E. coli and S. aurous. Obtained results indicated that the synthesized NPs, can be utilized in various areas.

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Facile Photochemical Syntheses of Conjoined Nanotwin Gold-Silver Particles within a Biologically-Benign Chitosan Polymer

Nanomaterials ◽

10.3390/nano9040596 ◽

2019 ◽

Vol 9 (4) ◽

pp. 596 ◽

Cited By ~ 2

Author(s):

Daniel K. Korir ◽

Bharat Gwalani ◽

Abel Joseph ◽

Brian Kamras ◽

Ravi K. Arvapally ◽

...

Keyword(s):

Second Step ◽

Silver Surface ◽

Ag Nps ◽

Au Nps ◽

Stabilizing Agents ◽

Shell Nanostructures ◽

Photochemical Method ◽

Gold Silver ◽

Bimetallic Nanostructures ◽

Irradiation Process

A simple photochemical method for making conjoined bi-metallic gold-silver (Au/Ag) nanotwins, a new breed of nanoparticles (NPs), is developed. To the best of our knowledge, the photochemical method resulted in distinct, conjoined, bimetallic nanotwins that are different from any well-established alloyed or core-shell nanostructures in the literature. The conjoined Au-Ag NPs possessed surface plasmon resonance (SPR) properties of both metals. The bimetallic nanostructures possessing distinctive optical properties of both metals were obtained using Au NPs as seeds in the first step, followed by the addition of a silver precursor as feed in the second step during a photochemical irradiation process. In the first step, small, isotropic or large, anisotropic Au NPs are generated by photoinduced reduction within a biocompatible chitosan (CS) polymer. In the second step, a silver precursor (AgNO3) is added as the feed to the AuNPs seed, followed by irradiation of the solution in the ice-bath. The entire photochemical irradiation process resulting in the formation of bimetallic Au-AgNPs did not involve any other reducing agents or stabilizing agents other than the CS polymer stabilizer. The small, conjoined Au-Ag bi-metallic NPs exhibited SPR with peak maxima centering at ~400 nm and ~550 nm, whereas the large conjoined nanoparticles exhibited SPR with peak maxima centering at ~400 nm, 550 nm, and 680 nm, characteristic of both gold and silver surface plasmons in solution. The tunability in the SPR and size of the bimetallic NPs were obtained by varying the reaction time and other reaction parameters, resulting in average sizes between 30 and 100 nm. The SPR, size, distribution, and elemental composition of the bi-metallic NPs were characterized using UV-Vis absorption, electron microscopy, and energy dispersive X-ray spectroscopy (EDS) studies.

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Doping Concentration Tuning and Plasmonic Optical Properties Modelling of Metal Nano Particles Utilizing FDTD Method

Materials Science Forum ◽

10.4028/www.scientific.net/msf.995.197 ◽

2020 ◽

Vol 995 ◽

pp. 197-202

Author(s):

Mehran Rafiee ◽

Subhash Chandra ◽

Hind Ahmed ◽

Aaron Glenn ◽

Conor Mc Loughlin ◽

...

Keyword(s):

Optical Properties ◽

Doping Concentration ◽

Radiative Decay ◽

Fdtd Method ◽

Nano Particles ◽

Noble Metal Nanoparticles ◽

Field Energy ◽

Ag Nps ◽

Gold And Silver Nanoparticles ◽

Au Nps

Among noble metal nanoparticles (MNPs), plasmonic effect of gold and silver nanoparticles (Au NPs and Ag NPs) is interesting to study due to their high near-field energy. This makes them excellent particles to absorb and scatter incident radiation in optical applications such as coupling them to fluorescent emitters to enhance their radiative decay and emission rate. This paper reviews and studies the methodology required for tuning the doping concentration and modelling plasmonic optical properties of Au NPs and Ag NPs by using finite difference time domain (FDTD) method. The frequency-dependent optical behaviour of MNPs is discussed. Plasmonic optical properties of MNPs can be characterised by their dimension, shape and doping concentration. Dimension and shape of MNPs can be simply defined in FDTD space grid (known as Yee grid). However, tuning MNPs doping concentration is more challenging which is undertaken by changing the spacing between MNPs and lateral boundaries of FDTD Yee grid. This can be vastly useful in Au NPs and Ag NPs optical optimization and applications to estimate plasmonic resonance based on doping concentration of particles.

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An Immunosensor Based on Au-Ag Bimetallic NPs Patterned on a Thermal Resistant Flexible Polymer Substrate for In-Vitro Protein Detection

Polymers ◽

10.3390/polym11081257 ◽

2019 ◽

Vol 11 (8) ◽

pp. 1257 ◽

Cited By ~ 1

Author(s):

Wang ◽

Wei ◽

Tong ◽

He ◽

Bai ◽

...

Keyword(s):

Protein Detection ◽

Polymer Substrate ◽

Smart Devices ◽

Ag Nps ◽

Au Nps ◽

Flexible Polymer ◽

Gold Silver ◽

Flexible Polymer Substrate ◽

Vitro Protein

Nanosensors based on flexible polymers have emerged as powerful tools for next generation smart devices in the recent years. Here, we report a facile protocol to fabricate an immunosensor supported by a thermally resistant flexible polymer substrate (polyarylene ether nitrile, PEN). The immunosensor is a localized surface plasmon resonance (LSPR) optical sensor for in-vitro protein detection based on anti-body coated gold-silver bimetallic nanoparticles (Au-Ag NPs) immobilized on a PEN substrate. Plasmonic spectroscopy and morphological characterization show that the Au-Ag NPs essentially exhibit a more uniform size distribution and higher quality factors than those from single-component Au NPs. Furthermore, it should be noted that the robust PEN substrate in this nanosensor acts a flexible substrate to support Au-Ag NPs and immobilize the nanoparticles via quick thermal annealing at 290 °C. Thanks to these merits, a prostate-specific antigen (PSA) concentration as low as 1 ng/mL can be specifically discriminated via the prepared PEN/Au-Au NPs, which confirms that the protocol reported in this work can be readily adapted for the construction of various flexible immunosensors for different applications.

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Real-time in vivo imaging of size-dependent transport and toxicity of gold nanoparticles in zebrafish embryos using single nanoparticle plasmonic spectroscopy

Interface Focus ◽

10.1098/rsfs.2012.0098 ◽

2013 ◽

Vol 3 (3) ◽

pp. 20120098 ◽

Cited By ~ 31

Author(s):

Lauren M. Browning ◽

Tao Huang ◽

Xiao-Hong Nancy Xu

Keyword(s):

Embryonic Development ◽

Real Time ◽

Rational Design ◽

Dark Field ◽

Molecular Probes ◽

Noble Metal Nanoparticles ◽

Zebrafish Embryos ◽

Ag Nps ◽

Au Nps

Noble metal nanoparticles (NPs) show distinctive plasmonic optical properties and superior photostability, enabling them to serve as photostable multi-coloured optical molecular probes and sensors for real-time in vivo imaging. To effectively study biological functions in vivo , it is essential that the NP probes are biocompatible and can be delivered into living organisms non-invasively. In this study, we have synthesized, purified and characterized stable (non-aggregated) gold (Au) NPs (86.2 ± 10.8 nm). We have developed dark-field single NP plasmonic microscopy and spectroscopy to study their transport into early developing zebrafish embryos (cleavage stage) and their effects on embryonic development in real-time at single NP resolution. We found that single Au NPs (75–97 nm) passively diffused into the embryos via their chorionic pore canals, and stayed inside the embryos throughout their entire development (120 h). The majority of embryos (96 ± 3%) that were chronically incubated with the Au NPs (0–20 pM) for 120 h developed to normal zebrafish, while an insignificant percentage of embryos developed to deformed zebrafish (1 ± 1)% or dead (3 ± 3)%. Interestingly, we did not observe dose-dependent effects of the Au NPs (0–20 pM) on embryonic development. By comparing with our previous studies of smaller Au NPs (11.6 ± 0.9 nm) and similar-sized Ag NPs (95.4 ± 16.0 nm), we found that the larger Au NPs are more biocompatible than the smaller Au NPs, while the similar-sized Ag NPs are much more toxic than Au NPs. This study offers in vivo assays and single NP microscopy and spectroscopy to characterize the biocompatibility and toxicity of single NPs, and new insights into the rational design of more biocompatible plasmonic NP imaging probes.

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Gold/Silver-Polymer Hybrid Nanostructures as Thermoreversible Optical Sensors and Probes for the Quantification Radical Compounds

MRS Proceedings ◽

10.1557/opl.2015.833 ◽

2015 ◽

Vol 1802 ◽

pp. 41-44 ◽

Cited By ~ 1

Author(s):

Eun Chul Cho ◽

Ju A La ◽

Sora Lim ◽

Ji Eun Song

Keyword(s):

Optical Sensors ◽

Polymeric Materials ◽

Hybrid Nanostructures ◽

Stimuli Responsive ◽

Ag Nps ◽

Au Nps ◽

Optical Signals ◽

Gold Silver ◽

Wide Range ◽

Color Switching

ABSTRACTWe present gold (Au) and silver (Ag) nanoparticles (NPs) could be used not only for stimuli-responsive optical sensors but also for the quantification of radical compounds when these nanoparticles are suitably combined with polymeric materials. When Au NPs are assembled 2-dimensionally on the surface of hydrogel NPs which respond to temperatures, the hybrid NPs displayed thermoreversible multiple color switching. Accordingly, optical bandwidths of the hybrid NPs are reversibly changed with temperatures: with hybrid NPs assembled with 51 nm Au NPs, prominent optical signals are recorded at 900 nm at 50 °C while most of extinction signals are shown below 600 nm at room temperatures. In addition, we demonstrate the modification of Ag NPs’ surfaces (nanocubes and nanospheres) with polyelectrolytes (either positive or negative) could extend the quantifiable detection ranges of radical compounds. Through the surface modification of Ag NPs, the polyelectrolytes protect the Ag NPs by probably either retarding (forming diffusion barriers) or preventing (blocking/entrapping/scavenging) the arrival of radicals to Ag NPs or both. The roles of the polyelectrolytes are demonstrated by using radical compounds produced from tetrahydrofuran and H2O2. From the results, we could obtain calibration curves for the wide-range quantification of radical compounds.

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Green synthesis of silver nanoparticles: Characterization and its potential biomedical applications

Green Processing and Synthesis ◽

10.1515/gps-2021-0039 ◽

2021 ◽

Vol 10 (1) ◽

pp. 412-420

Author(s):

Mona S. Alwhibi ◽

Dina A. Soliman ◽

Manal A. Awad ◽

Asma B. Alangery ◽

Horiah Al Dehaish ◽

...

Keyword(s):

Silver Nanoparticles ◽

Aloe Vera ◽

Inhibition Zone ◽

Biologically Active ◽

Noble Metal Nanoparticles ◽

Biological Synthesis ◽

Ag Nps ◽

Mouse Melanoma ◽

Therapeutic Benefits ◽

Vis Spectroscopy

Abstract In recent times, research on the synthesis of noble metal nanoparticles (NPs) has developed rapidly and attracted considerable attention. The use of plant extracts is the preferred mode for the biological synthesis of NPs due to the presence of biologically active constituents. Aloe vera is a plant endowed with therapeutic benefits especially in skincare due to its unique curative properties. The present study focused on an environmental friendly and rapid method of phytosynthesis of silver nanoparticles (Ag-NPs) using A. vera gel extract as a reductant. The synthesized Ag-NPs were characterized by transmission electron microscopy (TEM), UV-Vis spectroscopy, Fourier transform infrared (FTIR), and dynamic light scattering (DLS). TEM micrographs showed spherical-shaped synthesized Ag-NPs with a diameter of 50–100 nm. The UV-Vis spectrum displayed a broad absorption peak of surface plasmon resonance (SPR) at 450 nm. The mean size and size distribution of the formed Ag-NPs were investigated using the DLS technique. Antibacterial studies revealed zones of inhibition by Ag-NPs of A. vera (9 and 7 mm) against Pseudomonas aeruginosa and Escherichia coli, respectively. Furthermore, the antifungal activity was screened, based on the diameter of the growth inhibition zone using the synthesized Ag-NPs for different fungal strains. Anticancer activity of the synthesized Ag-NPs against the mouse melanoma F10B16 cell line revealed 100% inhibition with Ag-NPs at a concentration of 100 µg mL−1. The phytosynthesized Ag-NPs demonstrated a marked antimicrobial activity and also exhibited a potent cytotoxic effect against mouse melanoma F10B16 cells. The key findings of this study indicate that synthesized Ag-NPs exhibit profound therapeutic activity and could be potentially ideal alternatives in medicinal applications.

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State-of-art of silver and gold nanoparticles synthesis routes, characterization and applications: a review

Zeitschrift für Physikalische Chemie ◽

10.1515/zpch-2021-3084 ◽

2021 ◽

Vol 0 (0) ◽

Author(s):

Faisal Ali ◽

Muhammad Hamza ◽

Munawar Iqbal ◽

Beriham Basha ◽

Norah Alwadai ◽

...

Keyword(s):

Electron Microscope ◽

X Rays ◽

Ag Nps ◽

Au Nps ◽

Advantages And Disadvantages ◽

Transmission Electron ◽

Synthesis Properties ◽

Synthesis Routes ◽

Synthesis Approach ◽

Comprehensive Study

Abstract To date, the noble metal-based nanoparticles have been used in every field of life. The Au and Ag nanoparticles (NPs) have been fabricated employing different techniques to tune the properties. In this study, the methodologies developed and adopted for the fabrication of Au and Ag have been discussed, which include physical, chemical and biological routes. The Au and Ag characteristics (morphology, size, shape) along with advantages and disadvantages are discussed. The Au and Ag NPs catalytic and biomedical applications are discussed. For the Ag and Au NPs characterization, SEM (scanning electron microscope), TEM (transmission electron microscope), FTIR (Fourier transform infra-red spectroscopy), XRD (X-rays diffraction) and DLS (dynamic light scattering) techniques are employed. The properties of Au and Ag NPs found dependent to synthesis approach, i.e., the size, shape and morphologies, which showed a promising Catalytic, drug delivery and antimicrobial agent applications. The review is a comprehensive study for the comparison of Au and Ag NPs synthesis, properties and applications in different fields.

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Au-on-Ag nanostructure for in-situ SERS monitoring of catalytic reactions

Nanotechnology ◽

10.1088/1361-6528/ac47d2 ◽

2022 ◽

Author(s):

Shuyue He ◽

Di Wu ◽

Siwei Chen ◽

Kai Liu ◽

Eui-Hyeok Yang ◽

...

Keyword(s):

Catalytic Activity ◽

Thermal Evaporation ◽

Reduction Process ◽

Ag Nps ◽

Au Nps ◽

Surface Enhanced ◽

Surface Enhanced Raman ◽

Enhanced Raman Scattering ◽

Raman Probe

Abstract Dual-functionality Au-on-Ag nanostructures (AOA) were fabricated on a silicon substrate by first immobilizing citrate-reduced Ag nanoparticles (Ag NPs, ~43 nm in diameter), followed by depositing ~7 nm Au nanofilms (Au NFs) via thermal evaporation. Au NFs were introduced for their catalytic activity in concave-convex nano-configuration. Ag NPs underneath were used for their significant enhancement factor (EF) in surface-enhanced Raman scattering (SERS)-based measurements of analytes of interest. Rhodamine 6G (R6G) was utilized as the Raman-probe to evaluate the SERS sensitivity of AOA. The SERS EF of AOA is ~37 times than that of Au NPs. Using reduction of 4-nitrothiophenol (4-NTP) by sodium borohydride (NaBH4) as a model reaction, we demonstrated the robust catalytic activity of AOA as well as its capacity to continuously monitor via SERS the disappearance of reactant 4-NTP, emergence and disappearance of intermediate 4, 4’-DMAB, and the appearance of product 4-ATP throughout the reduction process in real-time and in situ.

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