Crystalline Silver Nanoparticles by Using Polygala tenuifolia Root Extract as a Green Reducing Agent.

Due to the emergence of multidrug-resistant bacteria, silver nanoparticles (AgNPs) have found interest as a new category of antibacterial agents. The toxicity of the chemicals involved in the commonly employed chemical methods for synthesizing AgNPs present limitations for subsequent pharmaceutical and biomedical applications. In this report, 70% aqueous ethanol extracts of Polygala tenuifolia root were used to reduce Ag+1 ions for AgNPs synthesis. The as-synthesized AgNPs were characterized via UV-Visible spectrophotometry, high resolution transmission electron microscopy, atomic force microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy. A strong surface plasmon resonance band was observed at 414 nm. Images from the high resolution transmission electron microscopy and atomic force microscopy demonstrated the spherical and irregular shapes of the AgNPs were synthesized. The AgNP crystalline structure was confirmed by the strong diffraction peaks in the X-ray diffraction results and by the bright circular spots observed in selected-area electron diffraction, whose average diameter was measured to be 17.97 8.63 nm or 15.12 nm via high resolution transmission electron microscopy images or X-ray diffraction analysis, respectively. The as-synthesized AgNPs exerted the highest antibacterial activity against Escherichia coli among the tested Gram-positive and Gram-negative bacteria. The current method is eco-friendly, straightforward, cost-effective, biocompatible, and easily scaled up to produce of AgNPs for applications in the treatment of bacterial infections.

Silver Nanoparticles Synthesized Using Caesalpinia sappan Extract as Potential Novel Nanoantibiotics Against Methicillin-Resistant Staphylococcus aureus.

Silver nanoparticles (AgNPs) have been shown to be effective antibacterial agents against methicillin-resistant Staphylococcus aureus (MRSA). In this study, AgNPs were synthesized using Caesalpinia sappan extract as a reducing agent to convert Ag+ to AgNPs. Seven stabilizers (surfactants and polymers) were added during the reduction step to increase the colloidal stability and to enhance the antibacterial activity of the AgNPs. Spherical and amorphous particles were primarily observed, with estimated diameters ranging from 30.2 to 47.5 nm. X-ray diffraction confirmed the face centered cubic structures of the AgNPs. Among the employed stabilizers, the cationic surfactant cetyltrimethylammonium bromide (CTAB) exhibited the highest antibacterial activity against 19 strains of MRSA, followed by polyvinylpyrrolidone (PVP, average molecular weight of 10,000). In contrast, the anionic surfactants sodium dodecyl sulfate (SDS) and sodium dodecylbenzene sulfonate (NaDDBS) did not exhibit any significant antibacterial activity, suggesting that the cationic surfactant head group contributed to the higher antibacterial activity of the AgNPs against MRSA.

Green synthesis of gold nanoparticles using chlorogenic acid and their enhanced performance for inflammation.

Here we developed a novel green synthesis method for gold nanoparticles (CGA-AuNPs) using chlorogenic acid (CGA) as reductants without the use of other chemicals and validated the anti-inflammatory efficacy of CGA-AuNPs in vitro and in vivo. The resulting CGA-AuNPs appeared predominantly spherical in shape with an average diameter of 22.25±4.78nm. The crystalline nature of the CGA-AuNPs was confirmed by high-resolution X-ray diffraction and by selected-area electron diffraction analyses. High-resolution liquid chromatography/electrospray ionization mass spectrometry revealed that the caffeic acid moiety of CGA forms quinone structure through a two-electron oxidation causing the reduction of Au(3+) to Au(0). When compared to CGA, CGA-AuNPs exhibited enhanced anti-inflammatory effects on NF-κB-mediated inflammatory network, as well as cell adhesion. Collectively, green synthesis of CGA-AuNPs using bioactive reductants and mechanistic studies based on mass spectrometry may open up new directions in nanomedicine and CGA-AuNPs can be an anti-inflammatory nanomedicine for future applications. FROM THE CLINICAL EDITOR: Gold nanoparticles (Au NPs) have been shown to be very useful in many applications due to their easy functionalization capability. In this article, the authors demonstrated a novel method for the synthesis of gold nanoparticles using chlorogenic acid (CGA) as reductants. In-vitro experiments also confirmed biological activity of the resultant gold nanoparticles. Further in-vivo studies are awaited.

Root extracts of Polygala tenuifolia for the green synthesis of gold nanoparticles.

Traditional medicinal plants possess diverse active constituents for exerting their biological activities. Recently, the innovative applications of plant extracts have revealed their promise as 'green' reducing agents for the reduction of metal ions during the synthesis of metallic nanoparticles. Herein, we report the use of 70% ethanol extracts from Polygala tenuifolia roots as a 'green' reducing agent for the production of gold nanoparticles by reducing gold(III) chloride trihydrate. Gold nanoparticles were characterized using UV-Visible spectrophotometry, high-resolution transmission electron microscopy (HR-TEM), atomic force microscopy (AFM), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FT-IR). The gold nanoparticles had characteristic surface plasmon resonance bands at 535 nm. HR-TEM and AFM images revealed major spherical-shaped nanoparticles. The average diameter was measured to be 9.77±3.09 nm using HR-TEM images. The crystalline structure of the gold nanoparticles was confirmed through lattice fringes and circular spots within the selected area electron diffraction in the HR-TEM images along with the XRD peaks. The gold nanoparticles exhibited enhanced anticoagulant activity, as assessed by activated partial thromboplastin time. The current method is a straightforward, environmentally friendly, and inexpensive method for the production of gold nanoparticles using extracts from traditional medicinal plants.

Earthworm extracts utilized in the green synthesis of gold nanoparticles capable of reinforcing the anticoagulant activities of heparin.

Gold nanoparticles were obtained using a green synthesis approach with aqueous earthworm extracts without any additional reducing or capping agents. The gold nanoparticles were characterized using UV-visible spectrophotometry, high-resolution transmission electron microscopy, atomic force microscopy, field emission scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and inductively coupled plasma mass spectrometry. The anticoagulant activity of the gold nanoparticles was assessed using the activated partial thromboplastin time and was mildly enhanced by combining the gold nanoparticles with heparin. In addition to the generation of spherical nanoparticles with an average diameter of 6.13 ± 2.13 nm, cubic and block-shaped nanoparticles with an average aspect ratio, defined as the length divided by width, of 1.47 were also observed.

Biogenic silver nanoparticles with chlorogenic acid as a bioreducing agent.

We report the synthesis of biogenic silver nanoparticles using chlorogenic acid as a bioreducing agent. Chlorogenic acid is a polyphenol compound abundant in coffee. UV-Vis spectra showed the characteristic surface plasmon resonance band at 415 nm, indicating the successful synthesis of biogenic silver nanoparticles. Spherical and irregular shaped nanoparticles were observed with an average diameter of 19.29 +/- 8.23 nm. The reaction yield from silver ion to silver nanoparticles was observed as 95.43% by using inductively coupled plasma-mass spectrometry. Fourier transform infrared spectra revealed that the -C = O groups of chlorogenic acid may coordinate or complex into silver nanoparticles. Biogenic silver nanoparticles exerted higher antibacterial activity against Gram-negative bacteria than against Gram-positive bacteria. Interestingly, a comparable antibacterial activity to a standard antibiotic was observed against two strains of Pseudomonas aeruginosa (minimum inhibitory concentration of 0.66 microg/mL). The synergistic effect of a combination of silver nanoparticles and chlorogenic acid on antibacterial activity is obvious, leading to approximately 8-fold enhancement in the case of Pseudomonas aeruginosa when compared with chlorogenic acid alone. The present report suggests that a pure compound with a plant origin is capable of being a bioreducing agent for the synthesis of biogenic silver nanoparticles with superior antibacterial activity, opening up many applications in nanomedicine and nanobiotechnology.

Green synthesis and nanotopography of heparin-reduced gold nanoparticles with enhanced anticoagulant activity.

This paper reports on the green synthesis of heparin-reduced gold nanoparticles and their nanotopography as studied with atomic force microscopy. The study also evaluated the anticoagulant activity of the newly prepared gold nanoparticles. The heparin-reduced gold nanoparticles were homogeneous, showing characteristic surface plasmon resonance bands of approximately 523-527 nm, and their shapes were mostly spherical and amorphous. The average diameter of the nanoparticles measured from atomic force microscopic images was either 20.26 +/- 3.35 nm or 40.85 +/- 8.95 nm depending on the different precursor salts and heparin concentrations. Atomic force microscopic images revealed that the topography of the heparin polymer aggregated when deposited onto mica, resembling a chain of mountains. This characteristic nanotopography of the heparin disappeared after the synthesis of the gold nanoparticles was performed. Interestingly, prolonged prothrombin time, thrombin time, and activated partial thromboplastin time were observed in the heparin-reduced gold nanoparticles when compared to a control heparin, suggesting the enhancement of anticoagulant activity in heparin-reduced gold nanoparticles. Hence, the green synthesis of gold nanoparticles with heparin using a simple reaction step could be a viable procedure for enhancing heparin's anticoagulant activity.