Wanderson Keijok

Extracellular biosynthesis of silver nanoparticles using the cell-free filtrate of nematophagous fungus Duddingtonia flagrans

The biosynthesis of metallic nanoparticles (NPs) using biological systems such as fungi has evolved to become an important area of nanobiotechnology. Herein, we report for the first time the extracellular synthesis of highly stable silver NPs (AgNPs) using the nematophagous fungus Duddingtonia flagrans (AC001). The fungal cell-free filtrate was analyzed by the Bradford method and 3,5-dinitrosalicylic acid assay and used to synthesize the AgNPs in the presence of a 1 mM AgNO3 solution. They have been characterized by UV–Vis spectroscopy, X-ray diffraction, transmission electron microscopy, dynamic light scattering, Zeta potential measurements, Fourier-transform infrared, and Raman spectroscopes. UV–Vis spectroscopy confirmed bioreduction, while X-ray diffractometry established the crystalline nature of the AgNPs. Dynamic light scattering and transmission electron microscopy images showed approximately 11, 38 nm monodisperse and quasispherical AgNPs. Zeta potential analysis was able to show a considerable stability of AgNPs. The N–H stretches in Fourier-transform infrared spectroscopy indicate the presence of protein molecules. The Raman bands suggest that chitinase was involved in the growth and stabilization of AgNPs, through the coating of the particles. Our results show that the NPs we synthesized have good stability, high yield, and monodispersion.

The green synthesis of gold nanoparticle using extract of Virola oleifera

Background The green synthesis consists of an environmentally friendly method of producing gold nanoparticles (AuNP’s). Physical and chemical syntheses have energy intensive and may involve toxic chemicals, while biological techniques are cost-effective, clean, non-toxic and environmentally appropriate. Virola oleifera is widely used in folk medicine. The bark of the trunk when scraped produce a resin rich in phenolic compounds, which is used against bleeding hemorrhoids, cramping, and also has healing action of chronic wounds and ulcers, diarrhea and counter hemoptysis. It is known that the presence of phenolic extract gives the reducing action, but studies need to be done to understand what substances are involved and what the mechanisms of formation of newly synthesized nanoparticles. Thus, the aim of this study was to describe a new route for the synthesis of AuNP’s using resin of Virola oleifera with future application in nanoscience from the synthesis of nanoparticles for applications as nano biosensors.

Comparison between the synthesis of gold nanoparticles with sodium citrate and sodium tetraboreto

Background With gold nanoparticles (AuNPs) is possible to develop nanoscale devices that can interact with chemical and biological systems. The phenomenon explored in these nanosystems is called Localized Surface Plasmon Resonance (LSPR), which promotes electromagnetic wave oscillation electronics on these small metallic structures. It is interesting to note that this resonance is directly linked to the size of the nanoparticles, the nature of the dielectric material and support environment where the device is being studied [1,2]. This work makes a comparison between results obtained in the synthesis of AuNP’s reduction method using a Sodium Citrate (Na3C6H5O7) and Sodium Borohydride (NaBH4). Was expected to demonstrate the viability of these two reducing agents and highlight the potential differences obtained in each of the mechanisms. Since knowledge is the ability of stabilizing citrate ions and the strong reducing action of NaBH4 [3]. The dominance of this knowledge will provide the development of systems with particle size specific for various applications in biosensors.

Quantification of Inter-particle Spacing Caused by Thiol Self-Assembled Monolayers Using Transmission Electron Microscopy

AbstractNano-surface modification techniques have been increasingly reported in a multitude of applications. However, the metal-ligand interface can be difficult to characterize, mainly due to the inadequacy of analytical methodologies. Here, we analyze this interface using transmission electron microscopy, which can determine the thickness of the linkers. This work presents a comprehensive physical characterization of gold nanoparticles with modified surfaces using conventional transmission electron microscopy. We have successfully demonstrated a simple and reliable protocol for the quantification of inter-particle spacing caused by SAM thiol ligands bound onto AuNPs. This approach is based on the linear correlation of the distance between the gold nanoparticles and the length of 3-mercaptopropionic acid (MPA), 11-mercaptoundecanoic acid (MUA), and 16-mercaptohexadecanoic acid (MHA). Graphical Abstract

Virola oleifera-capped gold nanoparticles showing radical-scavenging activity and low cytotoxicity

The development of effective nanoparticle therapeutics has been hindered by their surface characteristics, such as hydrophobicity and charge. Therefore, the success of biomedical applications with nanoparticles is governed by the control of these characteristics. In this article, we report an efficient green capping method for gold nanoparticles (AuNPs) by a reduction with sodium citrate and capping with Virola oleifera (Vo), which is a green exudate rich in polyphenols and flavonoids. The Vo-capped AuNPs were characterized by UV, DLS, FTIR, Raman, TEM, DPPH, FRAP and their cytotoxicity was evaluated on the viability of Murine macrophage cell. The AuNPs had an average particle size of 15 nm and were stable over a long time, as indicated by their unchanged SPR and zeta potential values. These nanoparticles were assessed for their antioxidant potential using DPPH and FRAP and demonstrated the highest antioxidant activities and low cytotoxicity. We propose that the Virola oleifera-capped AuNPs have potential biomedical applications.

Facile Synthesis of Monodisperse Gold Nanocrystals Using Virola oleifera

AbstractThe development of new routes and strategies for nanotechnology applications that only employ green synthesis has inspired investigators to devise natural systems. Among these systems, the synthesis of gold nanoparticles using plant extracts has been actively developed as an alternative, efficient, cost-effective, and environmentally safe method for producing nanoparticles, and this approach is also suitable for large-scale synthesis. This study reports reproducible and completely natural gold nanocrystals that were synthesized using Virola oleifera extract. V. oleifera resin is rich in epicatechin, ferulic acid, gallic acid, and flavonoids (i.e., quercetin and eriodictyol). These gold nanoparticles play three roles. First, these nanoparticles exhibit remarkable stability based on their zeta potential. Second, these nanoparticles are functionalized with flavonoids, and third, an efficient, economical, and environmentally friendly mechanism can be employed to produce green nanoparticles with organic compounds on the surface. Our model is capable of reducing the resin of V. oleifera, which creates stability and opens a new avenue for biological applications. This method does not require painstaking conditions or hazardous agents and is a rapid, efficient, and green approach for the fabrication of monodisperse gold nanoparticles. Graphical AbstractThe Virola oleifera reduction method for the synthesis of gold nanoparticles (AuNP’s)

Ultrasensitive nanosensor based on gold nanoparticles to detect vascular endothelial growth factor (VEGF)

We report on the use of new biosensor that enable a surface Plasmon resonance (SPR) sensor to detec VEGF in tissue extracts and cell lysates. This sensor consist of gold nanoparticles functionalized with antibodies anti-VEGF. To analyze the optical properties and their sensing ability was held optical absorption experiments in band plasmon resonance. We demonstrate that this approach makes it possible for the SPR biosensor to detect VEGF in tissues at low concentrations.

Polarização plasmônica de superfície em nanopartículas de ouro

Atualmente a Ressonância de Plasmon de Superficie (SPR) vem proporcionando resultados significativos nas areas de sensores e efeito fotonico. Um caso particular de SPR e a Ressonância de Plasmon de Superficie Localizada, porem ao inves de ocorrer sobre um filme metalico fino manifesta-se em NPAu, gerando assim um efeito localizado que e entendido como uma oscilacao concorrente entre os eletrons livres no metal. Desse modo, a comunicacao e transmissao de energia de uma nanoparticula para outra ocorre de forma mais eficiente quando maior for a interacao de dipolo desses sistemas. Portanto, a adicao de um componente que promova o aumento da interacao das nanoparticulas por dipolo gera elevacao na absorbância desse sistema. Nesse trabalho foi explorado a interacao que ocorrer entre NPAu e ions de sulfeto. Devido a alta capacidade de interacao entre o enxofre e o ouro, as NPAu tornam-se mais coesas melhorando assim suas interacoes no sistema e, por consequencia, aumentando a interacao energetica entre as nanoparticulas. Tal comportamento apresenta caracteristicas interessantes com relacao a aplicacao em sensores e dispositivos tecnologicos.

Gold nanoparticles synthesis to application as nano biosensors

Background The particularities of gold nanoparticles (AuNP’s) have stimulated different areas of research in recent years. The exploitation of the optical properties, electronic and magnetic materials has allowed these his job in different fields of application, such as the construction of biosensors in gradual release system for drugs, lubricants, solar cells, catalysis and other [1]. The properties of the nanoparticles are dependent on the size and shape of the particles. The same material composition can be determined with different physical and chemical characteristics just modifying characteristics such as size, self-organization, crystalline structure and shape, the point of the material in the nanometer range show distinct physical and chemical properties of materials on the macroscopic scale [2]. The aim of this work was to optimize the synthesis of gold nanoparticles using the reduction method sodium citrate, assessing concentrations of this reducing agent and the synthesis time. The attempt is to develop a route to generate nanoparticles from a precursor and facilitate the use of these nanomaterials in biosensors.

Production and characterization of metal nanoparticles for chemical reduction in order to application in biological systems

Background Several studies have demonstrated the use of metallic nanomaterials with applications in the biological area with very promising results. Gold nanoparticles (AuNP’s) have attracted great interest from researchers due to its electronic properties, optical, thermal, and its great potential for application in physical, chemical and biological [1]. In general, the AuNP’s are prepared by chemical reduction starting from a precursor (usually HAuCl4) is a strong reducing agent. The shape and size of the nanoparticles depend on the synthesis process variables such as concentration of the reactants, temperature, pH, reaction time, and others. The same material composition can be determined with different physical and chemical characteristics just modifying characteristics such as size, self-organization, crystalline structure and shape, the point of the material in the nanometer range show distinct physical and chemical properties of materials on the macroscopic scale [2]. The aim of this work was to prepare and characterize gold nanoparticles using the method of chemical reduction with sodium borohydride (NaBH4) in order to evaluate the influence of the concentration of the reducing agent and the time of synthesis on the properties of NP’s. The proposal is to use the material generated to evaluate its bactericidal effect.