Diallyl disulphide-loaded spherical gold nanoparticles and acorn-like silver nanoparticles synthesised using onion extract: catalytic activity and cytotoxicity.

Onion (Allium cepa) extract was used for the green synthesis of gold and silver nanoparticles. Each colloidal solution exhibited surface plasmon resonance, with a peak at 532 nm for gold nanoparticles and 391 nm for silver nanoparticles. Microscopic results confirmed the presence of spherical shapes. The X-ray diffraction pattern demonstrated a face-centered cubic structure. Both nanoparticles had negative zeta potentials and retained colloidal stability in cell culture medium. Catalytic applications were evaluated for 4-nitrophenol reduction and methyl orange degradation reactions by monitoring with UV-visible spectrophotometry. Furthermore, the nanoparticles demonstrated no significant cytotoxicity against human pancreas ductal adenocarcinoma cells (PANC-1) and human colorectal adenocarcinoma cells (HT-29). PEGylation and diallyl disulphide loading of the gold and silver nanoparticles meaningfully reduced the cell viability of both cell lines. Furthermore, diallyl disulphide loading resulted in more cytotoxicity against PANC-1 cells than against HT-29 cells. Additionally, the gold nanoparticles were more cytotoxic than the silver nanoparticles upon diallyl disulphide loading. Interestingly, after PEGylation and diallyl disulphide loading, the silver nanoparticles exhibited acorn-like shapes, while the gold nanoparticles retained spherical shapes. This result suggested that nanoparticles green-synthesised by onion extract have possibilities as nanocatalysts and drug delivery nanocarriers for catalytic and nanomedicine applications.

Optimal design of lattice structures for controllable extremal band gaps.

This paper presents very large complete band gaps at low audible frequency ranges tailored by gradient-based design optimizations of periodic two- and three-dimensional lattices. From the given various lattice topologies, we proceed to create and enlarge band gap properties through controlling neutral axis configuration and cross-section thickness of beam structures, while retaining the periodicity and size of the unit cell. Beam neutral axis configuration and cross-section thickness are parameterized by higher order B-spline basis functions within the isogeometric analysis framework, and controlled by an optimization algorithm using adjoint sensitivity. Our optimal curved designs show much more enhanced wave attenuation properties at audible low frequency region than previously reported straight or simple undulated geometries. Results of harmonic response analyses of beam structures consisting of a number of unit cells demonstrate the validity of the optimal designs. A plane wave propagation in infinite periodic lattice is analyzed within a unit cell using the Bloch periodic boundary condition.

Sesquiterpenoids from Tussilago farfara Flower Bud Extract for the Eco-Friendly Synthesis of Silver and Gold Nanoparticles Possessing Antibacterial and Anticancer Activities.

Sesquiterpenoids from the flower bud extract of Tussilago farfara were effectively utilized as a reducing agent for eco-friendly synthesis of silver and gold nanoparticles. The silver and gold nanoparticles had a characteristic surface plasmon resonance at 416 nm and 538 nm, respectively. Microscopic images revealed that both nanoparticles were spherical, and their size was measured to be 13.57 ± 3.26 nm for the silver nanoparticles and 18.20 ± 4.11 nm for the gold nanoparticles. The crystal structure was determined to be face-centered cubic by X-ray diffraction. Colloidal stability of the nanoparticle solution was retained in a full medium, which was used in the cell culture experiment. The antibacterial activity result demonstrated that the silver nanoparticles showed better activity (two- to four-fold enhancement) than the extract alone on both Gram-positive and Gram-negative bacteria. Interestingly, the highest antibacterial activity was obtained against vancomycin-resistant Enterococci Van-A type Enterococcus faecium. Cytotoxicity on cancer cell lines confirmed that gold nanoparticles were more cytotoxic than silver nanoparticles. The highest cytotoxicity was observed on human pancreas ductal adenocarcinoma cells. Therefore, both nanoparticles synthesized with the sesquiterpenoids from T. farfara flower bud extract can be applicable as drug delivery vehicles of anticancer or antibacterial agents for future nanomedicine applications.

Fabrication of nanoribbons by dielectrophoresis assisted cold welding of gold nanoparticles on mica substrate.

Using alternating current electric fields, nanoribbons are fabricated from an aqueous suspension of gold nanoparticles (AuNPs) on mica substrate without resorting to further chemical functionalization of AuNPs. The potential and kinetic energies of AuNPs subjected to attractive forces from a mica substrate provide sufficient energy to pass the diffusion barrier of the gold atoms, which eventually leads to cold welding. A dielectrophoresis force exerted on polarizable particles in a non-uniform electric field contributes to the directed growth of the cold welding that occurs by adjusting the lattice structures of AuNPs. Depending on the concentration of the AuNP suspension, the frequency of the electric field, and the geometry of electrodes, various morphologies of nanoribbons are fabricated. It turns out that the welded region is nearly perfect to provide the same crystal orientation and strength as the rest of the nanostructures, which can be extensively utilized in the fabrication of various nanostructures.

Upcycling of jellyfish (Nemopilema nomurai) sea wastes as highly valuable reducing agents for green synthesis of gold nanoparticles and their antitumor and anti-inflammatory activity.

Due to its tentacle poison and huge body, giant jellyfish (Nemopilema nomurai) poses challenging issues to the environment and ecosystems. Here we developed, upcycling a giant jellyfish extract as a reducing agent, a green synthetic method of gold nanoparticles (JF-AuNPs) which possess biological activities. The colloidal solutions of JF-AuNPs were blue, violet, purple and pink depending on the extract concentration. UV-visible spectra exhibited two surface plasmon resonance bands at 5 4 0 ∼ 550 nm and 810 nm. Spherical shapes with an average size of 35.2 ± 8.7 nm and triangular nanoplates with an average height of 70.5 ± 30.3 nm were observed. A face-centered cubic structure was confirmed by high-resolution X-ray diffraction. JF-AuNPs exhibited significant cytotoxic effect against HeLa cancer cells but not against normal cells such as NIH-3T3 and Raw 264.7 cells. In HeLa cells, JF-AuNPs decreased the phosphorylation of AKT and ERK, which are crucial for cell proliferation. Also, JF-AuNPs decreased NO secretion and iNOS expression levels, resulting in anti-inflammatory effects in LPS-inflamed macrophages. Collectively, we established a green synthesis of anti-tumorigenic and anti-inflammatory JF-AuNPs using the extract of jellyfish sea wastes. Thus, beneficial effects of JF-AgNPs must be weighed in further studies in vivo and it can be potent nanomedicine for future applications.

Platycodon saponins from Platycodi Radix (Platycodon grandiflorum) for the Green Synthesis of Gold and Silver Nanoparticles.

A green synthesis of gold and silver nanoparticles is described in the present report using platycodon saponins from Platycodi Radix (Platycodon grandiflorum) as reducing agents. Platycodin D (PD), a major triterpenoidal platycodon saponin, was enriched by an enzymatic transformation of an aqueous extract of Platycodi Radix. This PD-enriched fraction was utilized for processing reduction reactions of gold and silver salts to synthesize gold nanoparticles (PD-AuNPs) and silver nanoparticles (PD-AgNPs), respectively. No other chemicals were introduced during the reduction reactions, providing an entirely green, eco-friendly, and sustainable method. UV-visible spectra showed the surface plasmon resonance bands of PD-AuNPs at 536 nm and PD-AgNPs at 427 nm. Spherically shaped nanoparticles were observed from high-resolution transmission electron microscopy with average diameters of 14.94 ± 2.14 nm for PD-AuNPs and 18.40 ± 3.20 nm for PD-AgNPs. Minor triangular and other polygonal shapes were also observed for PD-AuNPs along with spherical ones. Atomic force microscopy (AFM) images also demonstrated that both nanoparticles were mostly spherical in shape. Curvature-dependent evolution was employed to enhance the AFM images and precisely measure the sizes of the nanoparticles. The sizes were measured as 19.14 nm for PD-AuNPs and 29.93 nm for PD-AgNPs from the enhanced AFM images. Face-centered cubic structures for both nanoparticles were confirmed by strong diffraction patterns from high-resolution X-ray diffraction analyses. Fourier transform infrared spectra revealed the contribution of -OH, aromatic C=C, C-O, and C-H functional groups to the synthesis. Furthermore, the catalytic activity of PD-AuNPs was assessed with a reduction reaction of 4-nitrophenol to 4-aminophenol in the presence of sodium borohydride. The catalytic activity results suggest the potential application of these gold nanoparticles as catalysts in the future. The green strategy reported in this study using saponins as reducing agents will pave new roads to develop novel nanomaterials with versatile applications.

Cold welding of gold nanoparticles on mica substrate: Self-adjustment and enhanced diffusion.

From the images of HR-TEM, FE-SEM, and AFM, the cold welding of gold nanoparticles (AuNPs) on a mica substrate is observed. The cold-welded gold nanoparticles of 25 nm diameters are found on the mica substrate in AFM measurement whereas the size of cold welding is limited to 10 nm for nanowires and 2~3 nm for nanofilms. Contrary to the nanowires requiring pressure, the AuNPs are able to rotate freely due to the attractive forces from the mica substrate and thus the cold welding goes along by adjusting lattice structures. The gold nanoparticles on the mica substrate are numerically modeled and whose physical characteristics are obtained by the molecular dynamic simulations of LAMMPS. The potential and kinetic energies of AuNPs on the mica substrate provide sufficient energy to overcome the diffusion barrier of gold atoms. After the cold welding, the regularity of lattice structure is maintained since the rotation of AuNPs is allowed due to the presence of mica substrate. It turns out that the growth of AuNPs can be controlled arbitrarily and the welded region is nearly perfect and provides the same crystal orientation and strength as the rest of the nanostructures.

Gallotannin-Capped Gold Nanoparticles: Green Synthesis and Enhanced Morphology of AFM Images.

Gold nanoparticles (AuNPs) were synthesized by a green method using a plant secondary metabolite, gallotannin. Gallotannin was used as a reducing and capping agent to convert gold ions into AuNPs for the generation of gallotannin-capped AuNPs (GT-AuNPs). This synthetic route is ecofriendly and eliminates the use of toxic chemical reducing agents. The characteristic surface plasmon resonance of the GT-AuNPs was observed at 536 nm in the UV-visible spectra. The face-centered cubic structure of GT-AuNPs was verified by X-ray diffraction analysis. The majority of the GT-AuNPs had a spherical shape with an average diameter of 15.93 ± 8.60 nm. Fourier transform infrared spectra suggested that the hydroxyl functional groups of gallotannin were involved in the synthesis of GT-AuNPs. The size and shape of nanoparticles can have a crucial impact on their biological, mechanical, and structural properties. Herein, we developed a modified anisotropic diffusion equation to selectively remove nanoscale experimental noise while preserving nanoscale intrinsic geometry information. To demonstrate the performance of the developed method, the ridge and valley lines were plotted by utilizing the principle curvatures. Compared to the original anisotropic diffusion and raw atomic force microscopy (AFM) experimental data, the developed modified anisotropic diffusion shows excellent performance in nanoscale noise removal while preserving the intrinsic aeometry of the nanoparticles.

Concentration Effect of Reducing Agents on Green Synthesis of Gold Nanoparticles: Size, Morphology, and Growth Mechanism.

Under various concentration conditions of reducing agents during the green synthesis of gold nanoparticles (AuNPs), we obtain the various geometry (morphology and size) of AuNPs that play a crucial role in their catalytic properties. Through both theoretical and experimental approaches, we studied the relationship between the concentration of reducing agent (caffeic acid) and the geometry of AuNPs. As the concentration of caffeic acid increases, the sizes of AuNPs were decreased due to the adsorption and stabilizing effect of oxidized caffeic acids (OXCAs). Thus, it turns out that optimal concentration exists for the desired geometry of AuNPs. Furthermore, we investigated the growth mechanism for the green synthesis of AuNPs. As the caffeic acid is added and adsorbed on the surface of AuNPs, the aggregation mechanism and surface free energy are changed and consequently resulted in the AuNPs of various geometry.

Tannic acid-mediated green synthesis of antibacterial silver nanoparticles.

The search for novel antibacterial agents is necessary to combat microbial resistance to current antibiotics. Silver nanoparticles (AgNPs) have been reported to be effective antibacterial agents. Tannic acid is a polyphenol compound from plants with antioxidant and antibacterial activities. In this report, AgNPs were prepared from silver ions by tannic acid-mediated green synthesis (TA-AgNPs). The reaction process was facile and involved mixing both silver ions and tannic acid. The absorbance at 423 nm in the UV-Visible spectra demonstrated that tannic acid underwent a reduction reaction to produce TA-AgNPs from silver ions. The synthetic yield of TA-AgNPs was 90.5% based on inductively coupled plasma mass spectrometry analysis. High-resolution transmission electron microscopy and atomic force microscopy images indicated that spherical-shaped TA-AgNPs with a mean particle size of 27.7-46.7 nm were obtained. Powder high-resolution X-ray diffraction analysis indicated that the TA-AgNP structure was face-centered cubic with a zeta potential of -27.56 mV. The hydroxyl functional groups of tannic acid contributed to the synthesis of TA-AgNPs, which was confirmed by Fourier transform infrared spectroscopy. The in vitro antibacterial activity was measured using the minimum inhibitory concentration (MIC) method. The TA-AgNPs were more effective against Gram-negative bacteria than Gram-positive bacteria. The MIC for the TA-AgNPs in all of the tested strains was in a silver concentration range of 6.74-13.48 µg/mL. The tannic acid-mediated synthesis of AgNPs afforded biocompatible nanocomposites for antibacterial applications.

Antibacterial nanocarriers of resveratrol with gold and silver nanoparticles.

This study focused on the preparation of resveratrol nanocarrier systems and the evaluation of their in vitro antibacterial activities. Gold nanoparticles (AuNPs) and silver nanoparticles (AgNPs) for resveratrol nanocarrier systems were synthesized using green synthetic routes. During the synthesis steps, resveratrol was utilized as a reducing agent to chemically reduce gold and silver ions to AuNPs and AgNPs. This system provides green and eco-friendly synthesis routes that do not involve additional chemical reducing agents. Resveratrol nanocarriers with AuNPs (Res-AuNPs) and AgNPs (Res-AgNPs) were observed to be spherical and to exhibit characteristic surface plasmon resonance at 547 nm and at 412-417 nm, respectively. The mean size of the nanoparticles ranged from 8.32 to 21.84 nm, as determined by high-resolution transmission electron microscopy. The face-centered cubic structure of the Res-AuNPs was confirmed by high-resolution X-ray diffraction. Fourier-transform infrared spectra indicated that the hydroxyl groups and C=C in the aromatic ring of resveratrol were involved in the reduction reaction. Res-AuNPs retained excellent colloidal stability during ultracentrifugation and re-dispersion, suggesting that resveratrol also played a role as a capping agent. Zeta potentials of Res-AuNPs and Res-AgNPs were in the range of -20.58 to -48.54 mV. Generally, against Gram-positive and Gram-negative bacteria, the Res-AuNPs and Res-AgNPs exhibited greater antibacterial activity compared to that of resveratrol alone. Among the tested strains, the highest antibacterial activity of the Res-AuNPs was observed against Streptococcus pneumoniae. The addition of sodium dodecyl sulfate during the synthesis of Res-AgNPs slightly increased their antibacterial activity. These results suggest that the newly developed resveratrol nanocarrier systems with metallic nanoparticles show potential for application as nano-antibacterial agents with enhanced activities.

Plant Extract (Bupleurum falcatum) as a Green Factory for Biofabrication of Gold Nanoparticles.

This work describes a biofabrication process for gold nanoparticles in which the plant extract (Bupleurum falcatum) is used as a reducing agent to convert gold ions to gold nanoparticles. Biofabricated gold nanoparticles with spherical shapes were observed with an average diameter of 10.5 ± 2.3 nm. The color of the gold nanoparticles was purple, with a surface plasmon resonance peak at 542 nm. The face-centered cubic structure of crystalline gold was confirmed by high-resolution X-ray diffraction patterns. The biofabricated gold nanoparticles demonstrated excellent catalytic activity towards the 4-nitrophenol reduction reaction. The current report suggests that plant extracts are valuable natural sources for the biofabrication of gold nanoparticles with excellent catalytic activities.

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.

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.

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.

Catechin-capped gold nanoparticles: green synthesis, characterization, and catalytic activity toward 4-nitrophenol reduction.

An eco-friendly approach is described for the green synthesis of gold nanoparticles using catechin as a reducing and capping agent. The reaction occurred at room temperature within 1 h without the use of any external energy and an excellent yield (99%) was obtained, as determined by inductively coupled plasma mass spectrometry. Various shapes of gold nanoparticles with an estimated diameter of 16.6 nm were green-synthesized. Notably, the capping of freshly synthesized gold nanoparticles by catechin was clearly visualized with the aid of microscopic techniques, including high-resolution transmission electron microscopy, atomic force microscopy, and field emission scanning electron microscopy. Strong peaks in the X-ray diffraction pattern of the as-prepared gold nanoparticles confirmed their crystalline nature. The catalytic activity of the as-prepared gold nanoparticles was observed in the reduction of 4-nitrophenol to 4-aminophenol in the presence of NaBH4. The results suggest that the newly prepared gold nanoparticles have potential uses in catalysis.

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.

Melamine nanosensing with chondroitin sulfate-reduced gold nanoparticles.

Gold nanoparticles were green-synthesized using a glycosaminoglycan, chondroitin sulfate, as the reducing agent by mixing Au3+ and chondroitin sulfate under heating. Chondroitin sulfate-reduced gold nanoparticles were characterized by UV-Vis spectrophotometry, high resolution transmission electron microscopy and atomic force microscopy. The yield of Au3+ to Au0 was measured as 80.1% by inductively coupled plasma-atomic emission spectroscopy. A mostly spherical shape, with an average diameter of 44.68 +/- 11.25 nm, was observed from the atomic force microscopy images. Using chondroitin sulfate-reduced gold nanoparticles, we developed a melamine nanosensor that provides a simplified method to detect melamine in infant formula. With an increase in the melamine concentration in the gold nanoparticle solution, the characteristic surface plasmon resonance band of gold nanoparticles at 530 nm decreased, whereas a new peak appeared at 620 nm. There was a linear relationship between the absorbance ratio (A620/A530) and the melamine concentration in the range of 0.1-10 microM. The practical use of the proposed method was verified by quantifying melamine spiked in real infant formula at concentrations as low as 12.6 ppb. The nanosensing of melamine using chondroitin sulfate-reduced gold nanoparticles can be a promising technique for quick on-site melamine screening of milk products.

Invertebrate water extracts as biocompatible reducing agents for the green synthesis of gold and silver nanoparticles.

We report the use of water extracts of two invertebrates, snail body and earthworm, as biocompatible reducing agents for the green synthesis of gold and silver nanoparticles. The reaction conditions were optimized by varying the extract concentration, gold ion or silver ion concentration, reaction time, and reaction temperature. The gold and silver nanoparticles exhibited their characteristic surface plasmon resonance bands. Mostly spherical and amorphous shapes of the nanoparticles were synthesized. The average diameters of the gold and silver nanoparticles were 4.56 +/- 1.81 nm and 11.12 +/- 5.25 nm, respectively, when the extract of snail body was used as the reducing agent. The earthworm extracts produced gold and silver nanoparticles with average diameters of 6.70 +/- 2.69 nm and 12.19 +/- 4.28 nm, respectively. This report suggests that the invertebrate natural products have potential as biocompatible reducing agents for the green synthesis of metallic nanoparticles. This utility would open up novel applications of invertebrate natural products as nanocomposites and in nanomedicine.