Synthesis of polysaccharide-stabilized gold and silver nanoparticles: a green method

Biosynthesis of metal nanoparticles using three marine plant species: anti-algal efficiencies against "Oscillatoria simplicissima"

This study aims at controlling of the cyanobacteria Oscillatoria simplicissima, those that produce neurotoxins and have negative impacts on the aquatic organisms, using biosynthesized metal nanoparticles (NPs). Silver-NPs (Ag-NPs) have been successfully biosynthesized using Nannochloropsis oculata and Tetraselmis tetrathele cultures. Also, Ag-NPs and iron oxide-NPs (Fe₃O₄-NPs) were synthesized by Halophila stipulacea aqueous extract. The structural composition of the different biosynthesized NPs was studied. The algae cultures and the extract were used as reductants of AgNO₃, and brown colors due to Ag-NP biosynthesis were observed. Silver signals were recorded in their corresponding EDX spectra. FTIR analyses showed that proteins in N. oculata and T. tetrathele cultures reduced AgNO₃, and aromatic compounds stabilized the biogenic Ag-NPs. H. stipulacea extract contains proteins and polyphenols that could be in charge for the reduction of silver and iron ions into nanoparticles and polysaccharides which stabilized the biosynthesized Ag-NPs and Fe₃O₄-NPs. The Ag-NPs biosynthesized by T. tetrathele cultures and H. stipulacea aqueous extract exerted outstanding negative impacts on O. simplicissima (optical density and total chlorophyll) and the Ag-NPs biosynthesized using N. oculata culture exerted the moderate performance. The study results suggest that the bioactive compounds present in the FTIR profiles of the Ag-NPs and or ionic silver may be the main contributors in their anti-algal effects. A trial to use the biosynthesized Fe₃O₄-NPs using H. stipulacea aqueous extract to separate Ag-NPs was successfully carried out. Since the synthesis and applications of nanomaterials is a hot subject of research, the study outcomes not only provide a green approach for the synthesis of metal-NPs but also open the way for more nanoparticle applications.

One-step preparation of banana powder/silver nanoparticles composite films

Silver nanoparticles (Ag-NPs) were synthesized using banana powder as a reducing and stabilizing agent, and banana/Ag-NPs composite films with different concentration of Ag-NPs were prepared simultaneously. The composite films were yellowish brown and exhibited characteristic plasmon resonance peak of Ag-NPs at 430 nm. The optical, mechanical, water vapor barrier, thermal stability, and antimicrobial properties of the composite films were greatly influenced by the concentration of Ag-NPs. The composite film with a silver concentration of 1.0 mM demonstrated the highest tensile strength, thermal stability, transparency, and water contact angle with the lowest water vapor permeability (1.36 ± 0.10 × 10^-9 g m/m² Pa s). Also, the composite films incorporated with 1.0 mM of Ag-NPs exhibited a strong antibacterial activity against both Gram-positive (Listeria monocytogenes) and Gram-negative (Escherichia coli) food-borne pathogenic bacteria.

Synthesis and magnetic properties of nanostructured metallic Co, Mn and Ni oxide materials obtained from solid-state metal-macromolecular complex precursors

Reaction of chitosan with metallic salts gives nanostructured Mn₂O₃, Co₃O₄ and NiO. Graphitic carbon is formed over the nanostructured oxides.

Formation and Physiochemical Properties of Silver Nanoparticles with Various Exopolysaccharides of a Medicinal Fungus in Aqueous Solution

Natural polysaccharides are the most widely used biopolymers for green synthesis of eco-friendly silver nanoparticles (AgNPs). In a previous study, a high molecular weight (MW) fraction of exopolysaccharides (EPS) produced by a medicinal fungus Cs-HK1 has been shown useful for green and facile synthesis of AgNPs in water. This study was to further evaluate the effects of molecular properties of EPS on the formation, stability and properties of AgNPs with different EPS fractions at various pH conditions. Three EPS fractions (P_0.5, P_2.0 and P_5.0: MW high to low and protein content low to high) were reacted with silver nitrate at various pH 3.0-8.0 in water. The most favorable pH range was 5.5-8.0 for the formation and stable dispersion of AgNPs. At a given pH, the maximum amount of AgNPs was produced with P_5.0, and the minimum with P_0.5. The shape, size and physiochemical properties of AgNPs were strongly affected by the molecular characteristics of EPS (MW and conformation). The results may be helpful for understanding the factors and mechanisms for formation of stable AgNPs with natural polysaccharides and the interactions between AgNPs and the polysaccharide hydrocolloids in water.

Laminating of chemically modified silan based nanosols for advanced functionalization of cotton textiles

As per to silver nanoparticles/silicon dioxide nanoparticles (SiO₂@AgNPs) properties (e.g., conductivity, reactant, adsorption, detachment and antimicrobial), many researchers were focused on its preparation technique. A core/shell of silicon dioxide and silver nanoparticles (SiO₂@AgNPs) has been prepared by facile route. The as synthesized core/shell nanoparticles were chemically modified with two different silan compounds, nominated, vinyltriethoxysilan (VTEOS) and (3-aminopropyl)trimethoxysilan (APTEOS). World class facilities such as XRD, FT-IR, TEM, Particle size, DLS, SEM techniques were utilized for the nanoparticles characterization. The nanoparticulate system comprises SiO₂@AgNPs, SiO₂@AgNPs/APTEOS were applied to cotton fabric using butantetracarboxylic acid (BTCA) as across-linking agent. While UV irradiation by photo initiator was used as crosslinking agent for SiO2@AgNPs/VTEOS on cotton fabrics. The Treated cotton fabrics were evaluated for their surface morphology and heat transfer ability as well as antibacterial activity. The obtained data prove that the core/shell was successfully prepared, with AgNPs in core. In addition, both silan compounds (APTEOS, VTEOS) were successfully reacted with the outer shell SiO₂. The results declared also that the treated fabrics exhibit a good antibacterial activity as well as good thermal properties.

Green Synthesis of Hierarchically Structured Silver-Polymer Nanocomposites with Antibacterial Activity

The in situ formation of silver nanoparticles (AgNPs) aided by chondroitin sulfate and the preparation of a hierarchically structured silver-polymer nanocomposite with antimicrobial activity is shown. Green synthesis of AgNPs is carried out by thermal treatment (80 and 90 °C) or UV irradiation of a chondroitin sulfate solution containing AgNO₃ without using any further reducing agents or stabilizers. Best control of the AgNPs size and polydispersity was achieved by UV irradiation. The ice-segregation-induced self-assembly (ISISA) process, in which the polymer solution containing the AgNPs is frozen unidirectionally, and successively freeze-drying were employed to produce the chondroitin sulfate 3D scaffolds. The scaffolds were further crosslinked with hexamethylene diisocyanate vapors to avoid water solubility of the 3D structures in aqueous environments. The antimicrobial activity of the scaffolds was tested against Escherichia coli. The minimum inhibitory concentration (MIC) found for AgNPs-CS (chondroitin sulfate) scaffolds was ca. 6 ppm.

Biosynthesis of silver nanoparticle and its application in cell wall disruption to release carbohydrate and lipid from C. vulgaris for biofuel production

•

The AgNP was successfully synthesised from soil isolated bacterium Bacillus subtilis.

•

The synthesised AgNPs were confirmed by UV-Spec, FTIR, TEM and XRD.

•

The AgNPs were successfully treated microalga to disrupt its cell wall to release lipids and carbohydrates.

•

The cell wall damages evidenced by LDH assay and SEM.

Microalgae are the fledging feedstocks yielding raw materials for the production of third generation biofuel. Assorted and conventional cell wall disruption techniques were helpful in extracting lipids and carbohydrates, nevertheless the disadvantages have led the biotechnologists to explore new process to lyse cell wall in a faster and an economical manner. Silver nanoparticles have the ability to break the cell wall of microalgae and release biomolecules effectively. Green synthesis of silver nanoparticles was performed using a novel bacterial isolate of Bacillus subtilis. Characterisation of nanosilver and its effect on cell wall lysis of microalgae were extensively analysed. Cell wall damage was confirmed by lactate dehydrogenase assay and visually by SEM analysis. This first piece of research work on direct use of nanoparticles for cell wall lysis would potentially be advantageous over its conventional approaches and a greener, cost effective and non laborious method for the production of biodiesel.

Ligand Assisted Stabilization of Fluorescence Nanoparticles; an Insight on the Fluorescence Characteristics, Dispersion Stability and DNA Loading Efficiency of Nanoparticles

This work reports on the ligand assisted stabilization of Fluospheres® carboxylate modified nanoparticles (FCMNPs), and subsequently investigation on the DNA loading capacity and fluorescence response of the modified particles. The designed fluorescence bioconjugate was characterized with enhanced fluorescence characteristics, good stability and large surface area with high DNA loading efficiency. For comparison purpose, bovine serum albumin (BSA) and polyethylene glycol (PEG) with three different length strands were used as cross linkers to modify the particles, and their DNA loading capacity and fluorescence characteristics were investigated. By comparing the performance of the particles, we found that the most improved fluorescence characteristics, enhanced DNA loading and high dispersion stability were obtained, when employing PEG of long spacer arm length. The designed fluorescence bioconjugate was observed to maintain all its characteristics under varying pH over an extended period of time. These types of bioconjugates are in great demand for fluorescence imaging and in vivo fluorescence biomedical application, especially when most of the as synthesized fluorescence particles cannot withstand to varying in vivo physiological conditions with decreases in fluorescence response and DNA loading efficiency.

Preparation of gold nanoparticles by novel bacterial exopolysaccharide for antibiotic delivery

AIM

To develop potent drug delivery agents to treat multidrug resistant (MDR) bacterial infections using gold nanoparticles (AuNPs) prepared by bacterial exopolysaccharide (EPS) being a reducing and stabilizing agent.

METHODS

Gold nanoparticles were prepared by EPS, extracted from Lactobacillus plantarum. AuNPs were characterized by UV-visible spectrophotometer, transmission electron microscope (TEM), zeta potential and Fourier transform infrared spectroscopy. Antibiotics used for functionalization of AuNPs were levofloxacin, cefotaxime, ceftriaxone and ciprofloxacin. The resulted functionalized AuNPs were tested against various MDR bacteria by employing different assays such as well diffusion assay, minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC) and time killing assay.

KEY FINDINGS

The nanostructures exhibited excellent bactericidal activity and reduced MIC and MBC against MDR Gram positive and Gram negative bacteria compared to free drugs. Escherichia coli was the most susceptible MDR bacteria followed by Klebsiella pneumoniae and Staphylococcus aureus. TEM results revealed that the bactericidal activity of nanostructures could be mediated by penetration, loss of cytoplasmic contents and cell lysis.

SIGNIFICANCE

Antibiotic functionalized nanostructures were more potent than free drugs and could be used as potent drug delivery vehicles.

Biosynthesis of tellurium nanoparticles by Lactobacillus plantarum and the effect of nanoparticle-enriched probiotics on the lipid profiles of mice

Hypercholesterolemia is an important risk factor contributing to atherosclerosis and coronary heart disease. Lactic acid bacteria have attracted much attention regarding their promising effect on serum cholesterol levels. Tellurium (Te) is a rare element that has also gained considerable interest for its biological effects. There have been some recent in vivo reports on the reduction effect of Te on cholesterol content. In this study, Lactobacillus plantarum PTCC 1058 was employed for the intracellular biosynthesis of Te NPs. The UV-visible spectrum of purified NPs showed a peak at 214 nm related to the surface plasmon resonance of the Te NPs. Transmission electron microscopy showed that spherical nanoparticles without aggregation had the average size of 45.7 nm as determined by the laser scattering method. The energy dispersive X-ray pattern confirmed the presence of Te atoms without any impurities. A significant reduction was observed in group which received L. plantarum with or without Te NPs during propylthiouracil and cholesterol diet in compare with the control group which received just propylthiouracil and cholesterol. The levels of triglycerides also remarkably decrease (p<0.05) in mice given L. plantarum with intracellular Te NPs.

Investigation of factors affecting the synthesis of nano-cadmium sulfide by pulsed laser ablation in liquid environment

Pulsed laser ablation in a liquid medium is a promising technique as compared to the other synthetic methods to synthesize different materials in nanoscale form. The laser parameters (e.g., wavelength, pulse width, fluence, and repetition frequency) and liquid medium (e.g., aqueous/nonaqueous liquid or solution with surfactant) were tightly controlled during and after the ablation process. By optimizing these parameters, the particle size and distribution of materials can be adjusted. The UV-vis absorption spectra and weight changes of targets were used for the characterization and comparison of products.

Solvent-less method for efficient photocatalytic α-Fe2O3 nanoparticles using macromolecular polymeric precursors

Efficient photocatalytic degradation of persistent cationic dye pollutants under visible light is possible with Fe₂O₃ nanoparticles formed by solvent-less synthesis using macromolecular precursor design.

Aggregation of layered double hydroxide nanoparticles in the presence of heparin: towards highly stable delivery systems

Heparin coating significantly enhanced the colloidal stability of layered double hydroxide nanoparticles.

Application of silver nanoparticles for a highly selective colorimetric assay of endrin in water and food samples based on stereoselective endo-recognition

We report a novel and facile strategy for a highly stereoselective colorimetric assay for the detection of endrin pesticide in water and food samples using sucrose capped silver nanoparticles (AgNPs).

Reversible encapsulation of silver nanoparticles into the helix of amylose (water soluble starch)

Natural biodegradable polymeric starch capped Ag-nanoparticles (AgNPs) were prepared by using extract of Dioscorea deltoidea in the presence of starch.

Silver nanoparticles in aquatic environments: Physiochemical behavior and antimicrobial mechanisms

Nanosilver (silver nanoparticles or AgNPs) has unique physiochemical properties and strong antimicrobial activities. This paper provides a comprehensive review of the physicochemical behavior (e.g., dissolution and aggregation) and antimicrobial mechanisms of nanosilver in aquatic environments. The inconsistency in calculating the Gibbs free energy of formation of nanosilver [ΔGf(AgNPs)] in aquatic environments highlights the research needed to carefully determine the thermodynamic stability of nanosilver. The dissolutive release of silver ion (Ag(+)) in the literature is often described using a pseudo-first-order kinetics, but the fit is generally poor. This paper proposes a two-stage model that could better predict silver ion release kinetics. The theoretical analysis suggests that nanosilver dissolution could occur under anoxic conditions and that nanosilver may be sulfidized to form silver sulfide (Ag2S) under strict anaerobic conditions, but more investigation with carefully-designed experiments is required to confirm the analysis. Although silver ion release is likely the main antimicrobial mechanism of nanosilver, the contributions of (ion-free) AgNPs and reactive oxygen species (ROS) generation to the overall toxicity of nanosilver must not be neglected. Several research directions are proposed to better understand the dissolution kinetics of nanosilver and its antimicrobial mechanisms under various aquatic environmental conditions.

Eco-friendly synthesis and catalytic application of chitosan/gold/carbon nanotube nanocomposite films

Novel eco-friendly chitosan nanocomposite membranes containing gold nanoparticles and carbon nanotubes (CNTs) have been synthesized to produce reusable catalytic membranes.

Green and energy-efficient methods for the production of metallic nanoparticles

In the last decade, researchers paid great attention to the concept of "Green Chemistry", which aims at development of efficient methods for the synthesis of nanoparticles (NPs) in terms of the least possible impact on human life and environment. Generally, several reagents including precursors, reducing agents, stabilizing agents and solvents are used for the production of NPs and in some cases, energy is needed to reach the optimum temperature for reduction. Therefore, to develop a green approach, researchers had the opportunity to investigate eco-friendly reagents and new energy transfer techniques. In order to substitute the harmful reagents with green ones, researchers worked on different types of saccharides, polyols, carboxylic acids, polyoxometalates and extracts of various plants that can play the role of reducers, stabilizers or solvents. Also, there are some reports on using ultraviolet (UV), gamma and microwave irradiation that are capable of reducing and provide uniform heating. According to the literature, it is possible to use green reagents and novel energy transfer techniques for production of NPs. However, these new synthesis routes should be optimized in terms of performance, cost, product quality (shape and size distribution) and scale-up capability. This paper presents a review on most of the employed green reagents and new energy transfer techniques for the production of metallic NPs.

Green sonochemical synthesis of silver nanoparticles at varying concentrations of κ-carrageenan

A green sonochemical method was developed for preparing silver nanoparticles (Ag-NPs) in different concentrations of kappa carrageenan (κ-carrageenan). The κ-carrageenan was used as a natural eco-friendly stabilizer, and ultrasonic irradiation was used as a green reducing agent. The number of Ag-NPs increased with increasing κ-carrageenan concentrations. Formation of Ag/κ-carrageenan was determined by UV-visible spectroscopy where the surface plasmon absorption maximum was observed at 402 to 420 nm. The X-ray diffraction (XRD) analysis showed that the Ag-NPs are of a face-centered cubic structure. The Fourier transform infrared (FT-IR) spectrum indicated the presence of Ag-NPs in κ-carrageenan. Transmission electron microscopy (TEM) image for the highest concentration of κ-carrageenan showed the distribution of Ag-NPs with an average particle size near to 4.21 nm. Scan electron microscopy (SEM) images illustrated the spherical shape of the Ag-NPs. The use of photo irradiation provides a green and economic feature to this work.

Progress toward clonable inorganic nanoparticles

Pseudomonas moraviensis stanleyae was recently isolated from the roots of the selenium (Se) hyperaccumulator plant Stanleya pinnata. This bacterium tolerates normally lethal concentrations of SeO3(2-) in liquid culture, where it also produces Se nanoparticles. Structure and cellular ultrastructure of the Se nanoparticles as determined by cellular electron tomography shows the nanoparticles as intracellular, of narrow dispersity, symmetrically irregular and without any observable membrane or structured protein shell. Protein mass spectrometry of a fractionated soluble cytosolic material with selenite reducing capability identified nitrite reductase and glutathione reductase homologues as NADPH dependent candidate enzymes for the reduction of selenite to zerovalent Se nanoparticles. In vitro experiments with commercially sourced glutathione reductase revealed that the enzyme can reduce SeO3(2-) (selenite) to Se nanoparticles in an NADPH-dependent process. The disappearance of the enzyme as determined by protein assay during nanoparticle formation suggests that glutathione reductase is associated with or possibly entombed in the nanoparticles whose formation it catalyzes. Chemically dissolving the nanoparticles releases the enzyme. The size of the nanoparticles varies with SeO3(2-) concentration, varying in size form 5 nm diameter when formed at 1.0 μM [SeO3(2-)] to 50 nm maximum diameter when formed at 100 μM [SeO3(2-)]. In aggregate, we suggest that glutathione reductase possesses the key attributes of a clonable nanoparticle system: ion reduction, nanoparticle retention and size control of the nanoparticle at the enzyme site.

Biosynthesis of silver nanoparticles using Artocarpus elasticus stem bark extract

Background

Green approach in synthesizing metal nanoparticles has gain new interest from the researchers as metal nanoparticles were widely applied in medical equipment and household products. The use of plants in the synthesis of nanoparticles emerges as a cost effective and eco-friendly approach. A green synthetic route for the production of stable silver nanoparticles (Ag-NPs) by using aqueous silver nitrate as metal precursor and Artocarpus elasticus stem bark extract act both as reductant and stabilizer is being reported for the first time.

Results

The resultant Ag-NPs were characterized by UV–vis spectroscopy, powder X-Ray diffraction, transmission electron microscopy (TEM), scanning electron microscopy (SEM), and Fourier-transform infra-red (FT-IR). The morphological study by TEM and SEM shows resultant Ag-NPs in spherical form with an average size of 5.81 ± 3.80, 6.95 ± 5.50, 12.39 ± 9.51, and 19.74 ± 9.70 nm at 3, 6, 24, and 48 h. Powder X-ray diffraction showed that the particles are crystalline in nature, with a face-centered cubic structure. The FT-IR spectrum shows prominent peaks appeared corresponds to different functional groups involved in synthesizing Ag-NPs.

Conclusions

Ag-NPs were synthesized using a simple and biosynthetic method by using methanolic extract of A. elasticus under room temperature, at different reaction time. The diameters of the biosynthesis Ag-NPs depended on the time of reaction. Thus, with the increase of reaction time in the room temperature the size of Ag-NPs increases. From the results obtained in this effort, one can affirm that A. elasticus can play an important role in the bioreduction and stabilization of silver ions to Ag-NPs.Graphical abstract: