In vitro anti-bacterial and cytotoxic properties of silver-containing poly(L-lactide-co-glycolide) nanofibrous scaffolds

Electrospinning has recently emerged as a leading technique for the formation of nanofibrous structures made of organic and inorganic components. In this study, nanofibrous scaffolds were prepared by electrospining a bend solution of poly(L-lactide-co-glycolide) (PLGA) and silver nanoparticles in 1,1,1,3,3,3,-hexafluoro-2-propanol (HFIP). The resulting fibers ranged from 420 to 590 nm in diameter. To evaluate the possibility of using silver-containing PLGA as a tissue engineering scaffold, experiments on cell viability and antibacterial activity were carried out. As a result, PLGA nanofibrous scaffolds having silver nanoparticles of more than 0.5 wt% showed antibacterial effect against Staphylococcus aureus and Klebsiella pneumonia. Furthermore, silver-containing PLGA nanofibrous scaffolds showed viability, indicating their possible application in the field of tissue engineering.     

Silica-precipitating peptides isolated from a combinatorial phage display peptide library

Many biological organisms contain specialized structures composed of inorganic materials. Cellular processes in vivo facilitate the organized assembly of mineral building blocks into complex structures. The structural hierarchy and complexity across a range of length scales are providing new ideas and concepts for materials chemistry. Proteins that direct biomineralization can be used to control the production of nanostructured materials and facilitate the fabrication of new structures. Here, we demonstrate that some of the silica-binding peptides isolated from a combinatorial phage peptide display library can be used in precipitating silica from a solution of silicic acid. The results described in this report demonstrate that peptides displayed by phages act as templates in inorganic material synthesis and provide a means of understanding how some of the biological systems may be carrying out materials chemistry in vivo.     

The size control of silver nanocrystals with different polyols and its application to low-reflection coating materials

The size of silver nanocrystals in polyol synthesis can be simply controlled by tuning the viscosity of the reaction medium such as ethylene glycol, 1,2-propanediol, 1,4-butanediol and 1,5-pentanediol. We found that a higher viscose medium (1,5-pentanediol) led to monodispersed smaller particles thanks to the slow addition of silver atoms into the nuclei. Size-controlled silver nanocrystals of 30 nm were obtained in a viscosity controlled medium of 1,5-pentanediol to synthesize a low refractive index filler by coating with silica and subsequent etching of the silver core. The coated low-reflection layer from the hollow silica nanoparticles on polyethylene terephthalate (PET) film can greatly reduce the reflection of the PET film from 10% to 2% over the entire visible region.     

A novel technique for synthesis of silver nanoparticles by laser-liquid interaction

Ultrafine particles of many materials have received much attention over the last few years by researchers because of their unique physical and mechanical properties due to increased surface area to volume ratio. A novel laser–liquid interaction technique has been developed to synthesize silver nanoparticles from inexpensive silver nitrate solution in distilled water. The shape, size distribution, microchemistry and crystal structure of the silver nanoparticles were studied using X-ray diffraction, scanning electron microscopy and electron probe X-ray microanalysis.     

Bio-inspired strategy for on-surface synthesis of silver nanoparticles for metal/organic hybrid nanomaterials and LDI-MS substrates

A strategy for the on-surface synthesis of silver nanoparticles (AgNPs) on a variety of two-?to three-dimensional material surfaces, utilizing polydopamine, an emerging surface modifying agent, is reported in this paper. This material-independent platform for AgNP synthesis is useful for fabricating organic/inorganic hybrid nanomaterials and for preparing substrates for laser desorption-ionization time-of-flight mass spectrometry (LDI-ToF MS).     

Antimicrobial coatings — obtaining and characterization

In this paper, we present inorganic–organic hybrid coatings with polymer matrix (water soluble) that contain silver nanoparticles (AgNPs). The structure and morphology of coating materials were determined by infrared spectroscopy (FT–IR) and scanning electron microscopy (SEM). Therefore, the antimicrobial activities and mechanisms of coatings for several pathogenic bacteria (Bacilius cereus and Staphylococcus aureus) were investigated. It was demonstrated that the obtained material with silver nanoparticles keep their antimicrobial effect even if they are subjected to several cycles of washing with water and detergent.     

Submonolayer and single crystal film from ligand-stabilized silver nanoparticles

Ligand-stabilized silver nanoparticles were synthesized by a method of ultraviolet light irradiation reduction from a parent solution containing inorganic silver salt, then deposited on carbon coated copper microscope grid by electrophoretic technique. All samples were examined on transmission electron microscope. The results indicate that when the parent solution was irradiated for 5 min a submonolayer of silver nanoparticles was obtained; however, when the parent solution was irradiated for 10 min single crystal silver films were formed. The mechanisms about formation of the submonolayer of nanoparticles and the single crystal silver films were discussed.     

自组装制备有机/无机层状复合材料

自然界中形成的生物材料在结构和性能上具有优异的配备性。模仿生物矿化的形成机制,利用自组装原理能够仿生合成出性能优良和具有多级结构特点的有机/无机界面层状复合材料。本文在总结近年来最新研究的成果上,简要介绍了自组装和生物矿化的机理,重点阐述了基于无机相层的自组装和以有机大分子为模板自组装制备有机／无机层状复合材料两种合成连径,并对未来的发展趋势做了展望。     

Biosynthesis of gold and silver nanoparticles using Emblica Officinalis fruit extract, their phase transfer and transmetallation in an organic solution

The design, synthesis and characterization of biologically synthesized nanomaterials have become an area of significant interest. In this paper, we report the extracellular synthesis of gold and silver nanoparticles using Emblica Officinalis (amla, Indian Gooseberry) fruit extract as the reducing agent to synthesize Ag and Au nanoparticles, their subsequent phase transfer to an organic solution and the transmetallation reaction of hydrophobized silver nanoparticles with hydrophobized chloroaurate ions. On treating aqueous silver sulfate and chloroauric acid solutions with Emblica Officinalis fruit extract, rapid reduction of the silver and chloroaurate ions is observed leading to the formation of highly stable silver and gold nanoparticles in solution. Transmission Electron Microscopy analysis of the silver and gold nanoparticles indicated that they ranged in size from 10 to 20 nm and 15 to 25 nm respectively. Ag and Au nanoparticles thus synthesized were then phase transferred into an organic solution using a cationic surfactant octadecylamine. Transmetallation reaction between hydrophobized silver nanoparticles and hydrophobized chloroaurate ions in chloroform resulted in the formation of gold nanoparticles.     

The bio-inspired approach to controllable biomimetic synthesis of silver nanoparticles in organic matrix of chitosan and silver-binding peptide (NPSSLFRYLPSD)

Inspired by organic matrices in some life systems which can operate as templates for biosynthesis organic materials with uniform size and morphology, in our experiment, chitosan was combined with AG4 peptide (NPSSLFRYLPSD) to form a simple organic matrix, which was used as a template to synthesize particle size and morphology-controlling silver nanoparticles. The results of UV–vis determination and TEM observation indicated that uniform spherical silver nanoparticles with about 5 nm in size were obtained at the certain concentration of chitosan and silver ions. Hence, it is possible to control the size and morphology of silver nanoparticles at a certain extent by adjusting the concentration of chitosan and silver ions. In addition, triangle and hexagonal silver nanoparticles ranging from 20 nm to 60 nm in size appeared in different conditions. The advantage of this biomimetic synthesis of silver nanoparticles is that the process could be accomplished under mild conditions rather than stringent conditions, such as high temperature, very high pressures and a toxic environment, which usually occurs with the traditional methods for preparing metal nanoparticles.     

Morphological changes in biomimetically synthesized hydroxyapatite and silver nanoparticles for medical applications

A precise control of morphology, which plays a significant role towards the application of materials, can be achieved by studying the effects of macromolecules as nucleation templates for minerals in a biomineralization process. The present investigation aims to understand such effects on medically important materials. Thus, Silver (Ag) and Calcium hydroxyapatite [Ca₁₀(PO₄)₆(OH)₂] were synthesized in both biopolymer (gelatin) and synthetic polymer (PVA) media, with aqueous medium as the control to portray a collage of how the interface between the macromolecule and the mineral controls the final morphology of the materials. It was also observed that the change of morphology of the products does influence their performances in specific applications like antibacterial property of the nanoparticles of silver was found to the best when synthesized in aqueous media. Thus, we consider that the organic–inorganic interaction to be of vital significance in the synthesis of complex shapes and sizes of nanoparticles for important applications. This article is dedicated to Professor T. R. Anantharaman a great teacher and founder of the school of research at the Department of Metallurgical Engineering, Banaras Hindu University (BHU). Interaction with this eminent visionary has greatly influenced our scientific and spiritual thinking.     

Phyto‐fabrication,purification, characterisation,optimisation, and biological competence of nano‐silver

Published studies indicate that virtually any kind of botanical material can be exploited to make biocompatible, safe, and cost‐effective silver nanoparticles. This hypothesis is supported by the fact that plants possess active bio‐ingredients that function as powerful reducing and coating agents for Ag+. In this respect, a phytomediation method provides favourable monodisperse, crystalline, and spherical particles that can be easily purified by ultra‐centrifugation. However, the characteristics of the particles depend on the reaction conditions. Optimal reaction conditions observed in different experiments were 70–95 °C and pH 5.5–8.0. Green silver nanoparticles (AgNPs) have remarkable physical, chemical, optical, and biological properties. Research findings revealed the versatility of silver particles, ranging from exploitation in topical antimicrobial ointments to in vivo prosthetic/organ implants. Advances in research on biogenic silver nanoparticles have led to the development of sophisticated optical and electronic materials with improved efficiency in a compact configuration. So far, eco‐toxicity of these nanoparticles is a big challenge, and no reliable method to improve the toxicity has been reported. Therefore, there is a need for reliable models to evaluate the effect of these nanoparticles on living organisms.     

Towards understanding biomineralization: calcium phosphate in a biomimetic mineralization process

Abstract Biomineralization processes result in organic/inorganic hybrid materials with complex shapes, hierarchical structures, and superior material properties. Recent developments in biomineralization and biomaterials have demonstrated that calcium phosphate particles play an important role in the formation of hard tissues in nature. In this paper, current concepts in biomineralization, such as nano assembly, biomimetic shell structure, and their applications are introduced. It is confirmed experimentally that enamel- or bone-liked apatite can be achieved by oriented aggregations using nano calcium phosphates as starting materials. The assembly of calcium phosphate can be either promoted or inhibited by different biomolecules so that the kinetics can be regulated biologically. In this paper, the role of nano calcium phosphate in tissue repair is highlighted. Furthermore, a new, interesting result on biomimetic mineralization is introduced, which can offer an artificial shell for living cells via a biomimetic method.     

Polymer-Mediated Synthesis of Fine-Sized Cobalt Particles

A novel method to synthesize monodisperse, fine-sized cobalt particles (average particle size 200 nm) by a polymer matrix (not commonly known for chemical chelation)-mediated sodium borohydride reduction of cobalt chloride has been demonstrated and discussed. As against the conventional concept of using a supramolecule as a growth Poisson during the crystallization of inorganic salt from solution, the present procedure adopts the path very similar to biomineralization. The polymer matrix chelates the cobalt ions by a combined process of physical entrapment and chemical chelation. The process leads to a controlled nucleation and ordered growth of cobalt salt in polymer matrix. Orderly grown cobalt salt on reduction yields monodisperse cobalt particles having uniform size and morphology.     

Monodisperse Ag@SiO2 core-shell nanoparticles as active inhibitors for marine anticorrosion applications

Monodisperse Ag@SiO2 core-shell structured nanoparticles were firstly utilized as a novel corrosion inhibitor for marine anticorrosion applications. The related marine anticorrosion properties were evaluated with an electrochemical noise (ECN) analysis during 2 weeks of accelerated immersion tests in natural seawater with the addition of various inorganic salts and nutriments. The experimental results indicate that the corrosion activity is markedly reduced by nearly 1-3 orders of magnitude owing to the introduction of Ag@SiO2 core-shell nanoparticles into coating. The inhibition efficiency of corrosion can reach as high as about 99%. More importantly, such a coating exhibits an excellent long-term sustained marine anticorrosion effect. So it could be reasonably inferred that silver cores as active inhibitors effectively prevent the corrosion damage from microorganisms, while silica shells act as a good protection for silver nanoparticles, delay the release of silver ions, and also function as the corrosion inhibiting action for inorganic salts. Therefore, this would make monodisperse Ag@SiO2 core-shell nanoparticles a potential and promising corrosion inhibitor for developing future advanced multifunctional coatings.     

A new bio-inspired route to metal-nanoparticle-based heterogeneous catalysts

Onion-type multilamellar vesicles are made of concentric bilayers of organic surfactant and are mainly known for their potential applications in biotechnology. They can be used as microreactors for the spontaneous and controlled production of metal nanoparticles. This process does not require any thermal treatment and, hence, it is also attractive for material sciences such as heterogeneous catalysis. In this paper, silver-nanoparticle-based catalysts are prepared by transferring onion-grown silver nanoparticles onto inorganic supports. The resulting materials are active in the total oxidation of benzene, attesting that this novel bio-inspired concept is promising in inorganic catalysis.     

Nanosilver particle formation on a high surface area titanate

Titanium based molecular sieves, such as ETS-10, have the ability to exchange silver ions and subsequently support self assembly of stable silver nanoparticles when heated. We report that a high surface area sodium titanate (resembling ETS-2) displays a similar ability to self template silver nanoparticles on its surface. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) show high concentrations of silver nanoparticles on the surface of this sodium titanate, formed by thermal reduction of exchanged silver cations. The nanoparticles range in size from 4 to 12 nm, centered at around 6 nm. In addition to SEM and TEM, XRD and surface area analysis were used to characterize the material. The results indicate that this sodium titanate has a high surface area (>263 m2/g), and high ion exchange capacity for silver (30+ wt%) making it an excellent substrate for the exchange and generation of uniform, high-density silver nanoparticles.     

Biocide activity of diatom-silver nanocomposite

Diatom-nAg composites containing 1 wt.% of metallic silver nanoparticles (≤ 20 nm) have been obtained by a colloidal route and chemical reduction. This nanostructured powder has proved to be a selective green inorganic biocide which reduces the starting concentrations of Escherichia coli and Micrococcus luteus cultures by at least 5 orders of magnitude, while completely inactive against yeast. Diatom-nAg can be considered as a selective inorganic biocide particularly suitable for the food and pharmacological sectors. The silver nanoparticles are released from the diatom surface to the liquid media in a controlled manner, reaching a concentration (< 11 ppm) far below the toxicity limit for human cells.     

Quasi-linear assemblies of silver nanoparticles by highly localized anodic dissolution of copper in the hydrosol

The assembly of silver nanoparticles into quasi-linear superstructures in solution has been demonstrated. A small dc voltage applied to fine-tipped, L-shaped copper electrodes immersed in aqueous carboxylic acid-derivatized silver nanoparticle solution leads to the anodic dissolution of copper ions. The controlled release of Cu2+ ions within the gaps results in local screening of repulsive coulombic interactions between the silver nanoparticles and the consequent formation of aggregates that are extremely stable in time. Atomic force and transmission electron microscopy images of the silver nanoparticle solution after application of an electric field showed the presence of a large number of silver nanoparticle assemblies in open, quasi-linear structures. Such open structures do not form if Cu2+ ions are added directly to the silver nanoparticle solution.     

A facile synthetic route to aqueous dispersions of silver nanoparticles

Stable aqueous dispersions of silver nanoparticles have been synthesized from an organometallic precursor dissolved in an organic phase. Hydrogen gas is used to reduce the precursor to form silver nanoparticles which spontaneously transfer into an immiscible aqueous phase where they are stabilized. This route provides a simple pathway for the preparation of aqueous nanoparticle solutions and avoids production of the inorganic ions that are usually associated with aqueous methods. The effectiveness of a variety of aqueous stabilizing agents is evaluated. All products show plasmon absorption bands characteristic of silver nanoparticles and transmission electron microscopy reveals most particles to be below 40 nm in diameter.