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Microstructural, spectroscopic, and antibacterial properties of silver-based hybrid nanostructures biosynthesized using extracts of coriander leaves and seeds

View Article: PubMed Central - PubMed

ABSTRACT

Coriander leaves and seeds have been highly appreciated since ancient times, not only due to their pleasant flavors but also due to their inhibitory activity on food degradation and their beneficial properties for health, both ascribed to their strong antioxidant activity. Recently, it has been shown that coriander leaf extracts can mediate the synthesis of metallic nanoparticles through oxidation/reduction reactions. In the present study, extracts of coriander leaves and seeds have been used as reaction media for the wet chemical synthesis of ultrafine silver nanoparticles and nanoparticle clusters, with urchin- and tree-like shapes, coated by biomolecules (mainly, proteins and polyphenols). In this greener route of nanostructure preparation, the active biocompounds of coriander simultaneously play the roles of reducing and stabilizing agents. The morphological and microstructural studies of the resulting biosynthesized silver nanostructures revealed that the nanostructures prepared with a small concentration of the precursor Ag salt (AgNO3 =5 mM) exhibit an ultrafine size and a narrow size distribution, whereas particles synthesized with high concentrations of the precursor Ag salt (AgNO3 =0.5 M) are polydisperse and formation of supramolecular structures occurs. Fourier transform infrared and Raman spectroscopy studies indicated that the bioreduction of the Ag− ions takes place through their interactions with free amines, carboxylate ions, and hydroxyl groups. As a consequence of such interactions, residues of proteins and polyphenols cap the biosynthesized Ag nanoparticles providing them a hybrid core/shell structure. In addition, these biosynthesized Ag nanomaterials exhibited size-dependent plasmon extinction bands and enhanced bactericidal activities against both Gram-positive and Gram-negative bacteria, displaying minimal inhibitory Ag concentrations lower than typical values reported in the literature for Ag nanoparticles, probably due to the synergy of the bactericidal activities of the Ag nanoparticle cores and their capping ligands.

No MeSH data available.


Related in: MedlinePlus

Transmission electron microscopy (TEM) studies of sample L-5mM.Notes: (A) TEM micrograph. The inset is a low-magnification TEM image. (B) Histogram of the particle diameter distribution. (C) High-resolution TEM image. The inset is the Fourier-filtered image of the Ag nanoparticle highlighted by a dashed yellow square. The arrows and line segments in the inset indicate the interplanar distance observed in the high-resolution TEM image. (D) TEM image of the sample S-5mM. The inset shows the particle diameter distribution of this sample.Abbreviations: L-5mM, final colloid obtained using coriander leaf extract and 5 M AgNO3; S-5mM, sample obtained using extracts of coriander seeds and 5 M AgNO3 solution.
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f2-ijn-11-4787: Transmission electron microscopy (TEM) studies of sample L-5mM.Notes: (A) TEM micrograph. The inset is a low-magnification TEM image. (B) Histogram of the particle diameter distribution. (C) High-resolution TEM image. The inset is the Fourier-filtered image of the Ag nanoparticle highlighted by a dashed yellow square. The arrows and line segments in the inset indicate the interplanar distance observed in the high-resolution TEM image. (D) TEM image of the sample S-5mM. The inset shows the particle diameter distribution of this sample.Abbreviations: L-5mM, final colloid obtained using coriander leaf extract and 5 M AgNO3; S-5mM, sample obtained using extracts of coriander seeds and 5 M AgNO3 solution.

Mentions: Figure 2A depicts a representative TEM image of sample L-5mM. In this micrograph, the biosynthesized nanoparticles appear as well-dispersed dark dots embedded into an amorphous matrix associated to residual material of the coriander leaf extract. Most particles exhibited an ultrafine size with a mean diameter of 2.9(6) nm (Figure 2B represents the diameter distribution of these particles). However, a small fraction of the observed particles (<1%) exhibited sizes of several tens of nanometers (shown in the inset of Figure 2A). The appearance of these bigger particles could be reduced further by size-selection procedures such as ultracentrifugation. Figure 2C depicts a typical HRTEM of these nanoparticles showing lattice fringes associated to the fcc silver phase. Very similar features were observed for sample S-5mM (Figure 2D) with a mean diameter of 7(2) nm (shown in the inset of Figure 2D).


Microstructural, spectroscopic, and antibacterial properties of silver-based hybrid nanostructures biosynthesized using extracts of coriander leaves and seeds
Transmission electron microscopy (TEM) studies of sample L-5mM.Notes: (A) TEM micrograph. The inset is a low-magnification TEM image. (B) Histogram of the particle diameter distribution. (C) High-resolution TEM image. The inset is the Fourier-filtered image of the Ag nanoparticle highlighted by a dashed yellow square. The arrows and line segments in the inset indicate the interplanar distance observed in the high-resolution TEM image. (D) TEM image of the sample S-5mM. The inset shows the particle diameter distribution of this sample.Abbreviations: L-5mM, final colloid obtained using coriander leaf extract and 5 M AgNO3; S-5mM, sample obtained using extracts of coriander seeds and 5 M AgNO3 solution.
© Copyright Policy
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC5036574&req=5

f2-ijn-11-4787: Transmission electron microscopy (TEM) studies of sample L-5mM.Notes: (A) TEM micrograph. The inset is a low-magnification TEM image. (B) Histogram of the particle diameter distribution. (C) High-resolution TEM image. The inset is the Fourier-filtered image of the Ag nanoparticle highlighted by a dashed yellow square. The arrows and line segments in the inset indicate the interplanar distance observed in the high-resolution TEM image. (D) TEM image of the sample S-5mM. The inset shows the particle diameter distribution of this sample.Abbreviations: L-5mM, final colloid obtained using coriander leaf extract and 5 M AgNO3; S-5mM, sample obtained using extracts of coriander seeds and 5 M AgNO3 solution.
Mentions: Figure 2A depicts a representative TEM image of sample L-5mM. In this micrograph, the biosynthesized nanoparticles appear as well-dispersed dark dots embedded into an amorphous matrix associated to residual material of the coriander leaf extract. Most particles exhibited an ultrafine size with a mean diameter of 2.9(6) nm (Figure 2B represents the diameter distribution of these particles). However, a small fraction of the observed particles (<1%) exhibited sizes of several tens of nanometers (shown in the inset of Figure 2A). The appearance of these bigger particles could be reduced further by size-selection procedures such as ultracentrifugation. Figure 2C depicts a typical HRTEM of these nanoparticles showing lattice fringes associated to the fcc silver phase. Very similar features were observed for sample S-5mM (Figure 2D) with a mean diameter of 7(2) nm (shown in the inset of Figure 2D).

View Article: PubMed Central - PubMed

ABSTRACT

Coriander leaves and seeds have been highly appreciated since ancient times, not only due to their pleasant flavors but also due to their inhibitory activity on food degradation and their beneficial properties for health, both ascribed to their strong antioxidant activity. Recently, it has been shown that coriander leaf extracts can mediate the synthesis of metallic nanoparticles through oxidation/reduction reactions. In the present study, extracts of coriander leaves and seeds have been used as reaction media for the wet chemical synthesis of ultrafine silver nanoparticles and nanoparticle clusters, with urchin- and tree-like shapes, coated by biomolecules (mainly, proteins and polyphenols). In this greener route of nanostructure preparation, the active biocompounds of coriander simultaneously play the roles of reducing and stabilizing agents. The morphological and microstructural studies of the resulting biosynthesized silver nanostructures revealed that the nanostructures prepared with a small concentration of the precursor Ag salt (AgNO3 =5 mM) exhibit an ultrafine size and a narrow size distribution, whereas particles synthesized with high concentrations of the precursor Ag salt (AgNO3 =0.5 M) are polydisperse and formation of supramolecular structures occurs. Fourier transform infrared and Raman spectroscopy studies indicated that the bioreduction of the Ag&minus; ions takes place through their interactions with free amines, carboxylate ions, and hydroxyl groups. As a consequence of such interactions, residues of proteins and polyphenols cap the biosynthesized Ag nanoparticles providing them a hybrid core/shell structure. In addition, these biosynthesized Ag nanomaterials exhibited size-dependent plasmon extinction bands and enhanced bactericidal activities against both Gram-positive and Gram-negative bacteria, displaying minimal inhibitory Ag concentrations lower than typical values reported in the literature for Ag nanoparticles, probably due to the synergy of the bactericidal activities of the Ag nanoparticle cores and their capping ligands.

No MeSH data available.


Related in: MedlinePlus