The green synthesis of nanoparticles (NPs) using living cells is a promising and novelty tool in bionanotechnology. Chemical and physical methods are used to synthesize NPs; however, biological methods are preferred due to its eco-friendly, clean, safe, cost-effective, easy, and effective sources for high productivity and purity. High pressure or temperature is not required for the green synthesis of NPs, and the use of toxic and hazardous substances and the addition of external reducing, stabilizing, or capping agents are avoided. Intra- or extracellular biosynthesis of NPs can be achieved by numerous biological entities including bacteria, fungi, yeast, algae, actinomycetes, and plant extracts. Recently, numerous methods are used to increase the productivity of nanoparticles with variable size, shape, and stability. The different mechanical, optical, magnetic, and chemical properties of NPs have been related to their shape, size, surface charge, and surface area. Detection and characterization of biosynthesized NPs are conducted using different techniques such as UV-vis spectroscopy, FT-IR, TEM, SEM, AFM, DLS, XRD, zeta potential analyses, etc. NPs synthesized by the green approach can be incorporated into different biotechnological fields as antimicrobial, antitumor, and antioxidant agents; as a control for phytopathogens; and as bioremediative factors, and they are also used in the food and textile industries, in smart agriculture, and in wastewater treatment. This review will address biological entities that can be used for the green synthesis of NPs and their prospects for biotechnological applications.

Green Synthesis of Metallic Nanoparticles and Their Prospective Biotechnological Applications: an Overview

The use of fungi as reducing and stabilizing agents in the biogenic synthesis of silver nanoparticles is attractive due to the production of large quantities of proteins, high yields, easy handling, and low toxicity of the residues. Furthermore, this synthesis process coats the nanoparticles with biomolecules derived from the fungus, which can improve stability and may confer biological activity. The aim of this review is to describe studies in which silver nanoparticles were synthesized using fungi as reducing agents, discussing the mechanisms and optimization of the synthesis, as well as the applications. The literature shows that various species of fungus have potential for use in biogenic synthesis, enabling the production of nanoparticles with different characteristics, considering aspects such as their size, surface charge, and morphology. The synthesis mechanisms have not yet been fully elucidated, although it is believed that fungal biomolecules are mainly responsible for the process. The synthesis can be optimized by adjusting parameters such as temperature, pH, silver precursor concentration, biomass amount, and fungus cultivation time. Silver nanoparticles synthesized using fungi enable the control of pathogens, with low toxicity and good biocompatibility. These findings open perspectives for future investigations concerning the use of these nanoparticles as antimicrobials in the areas of health and agriculture.

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Synthesis of Silver Nanoparticles Mediated by Fungi: A Review.

During the last decade, metal nanoparticles (MtNPs) have gained immense popularity due to their characteristic physicochemical properties, as well as containing antimicrobial, anti-cancer, catalyzing, optical, electronic and magnetic properties. Primarily, these MtNPs have been synthesized through different physical and chemical methods. However, these conventional methods have various drawbacks, such as high energy consumption, high cost and the involvement of toxic chemical substances. Microbial flora has provided an alternative platform for the biological synthesis of MtNPs in an eco-friendly and cost effective way. In this article we have focused on various microorganisms used for the synthesis of different MtNPs. We also have elaborated on the intracellular and extracellular mechanisms of MtNP synthesis in microorganisms, and have highlighted their advantages along with their challenges. Moreover, due to several advantages over chemically synthesized nanoparticles, the microbial MtNPs, with their exclusive and dynamic characteristics, can be used in different sectors like the agriculture, medicine, cosmetics and biotechnology industries in the near future.

https://www.mdpi.com/1422-0067/19/12/4100/pdf

Biosynthesis of Metal Nanoparticles via Microbial Enzymes: A Mechanistic Approach.

An efficient biosynthesis process for the rapid production of nanoparticles would enable the development of a “microbial nanotechnology” for mass-scale production. In the present research, biological silver nanoparticle was synthesized extracellularly by using the fungus, Trichoderma longibrachiatum, where the cell filtrate of the fungus was used as a reducing and stabilizing agent in the process of nanoparticle synthesis. Different physical parameters such as fungal biomass concentration (1, 5, 10, 15, and 20 g), temperature (25, 28, and 33 °C), incubation time (0–120 h), and agitation (shaken or not shaken) were investigated, in order to determine the optimal conditions for nanoparticle biosynthesis. The stability and antifungal properties of the synthesized silver nanoparticles (AgNPs) were also determined. Data revealed that a combination of 10 g fungal biomass, a reaction temperature of 28 °C, a 72-h incubation time, and without shaking were the optimum conditions for the synthesis of the silver nanoparticles. Visual observation of brown color is an indication of silver nanoparticle production. UV–vis spectroscopy showed maximum absorption at 385 nm with the optimum conditions. Transmission electron microscopy (TEM) revealed the formation of monodispersed spherical shape with a mean diameter of 10 nm. Fourier transformation infrared (FTIR) showed bands at1634.92 and 3269.31 cm−1. Dynamic light scattering (DLS) supported that the Z-average size was 24.43 and 0.420 PdI value. Zeta potential showed − 19.7 mV with a single peak. The AgNPs synthesized through this biosystem approach were relatively stable up to 2 months after synthesis. The use of AgNPs as antifungal led to significant reductions in the number of forming colonies for many plant pathogenic fungi, with efficiencies reaching up to 90% against Fusarium verticillioides, Fusarium moniliforme, Penicillium brevicompactum, Helminthosporium oryzae, and Pyricularia grisea. However, further research should be carried out in order to determine the toxic effect of AgNPs before mass production and use of agricultural applications.

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Biosynthesis and characterization of silver nanoparticles using Trichoderma longibrachiatum and their effect on phytopathogenic fungi

The past decade has witnessed a phenomenal rise in nanotechnology research due to its broad range of applications in diverse fields including food safety, transportation, sustainable energy, environmental science, catalysis, and medicine. The distinctive properties of nanomaterials (nano-sized particles in the range of 1 to 100 nm) make them uniquely suitable for such wide range of functions. The nanoparticles when manufactured using green synthesis methods are especially desirable being devoid of harsh operating conditions (high temperature and pressure), hazardous chemicals, or addition of external stabilizing or capping agents. Numerous plants and microorganisms are being experimented upon for an eco–friendly, cost–effective, and biologically safe process optimization. This review provides a comprehensive overview on the green synthesis of metallic NPs using plants and microorganisms, factors affecting the synthesis, and characterization of synthesized NPs. The potential applications of metal NPs in various sectors have also been highlighted along with the major challenges involved with respect to toxicity and translational research.

Green Synthesis of Metallic Nanoparticles: Applications and Limitations

Silver nanoparticles (AgNPs) was evaluated for its possible effects on the incidence of seed rot disease of Faba bean, Tomato and Barley caused by the seed and soil borne fungus Fusarium oxysporium. The Silver nanoparticles were biosynthesized by the fungus Trichoderma longibrachiatum and characterized by UVVisible (UV-Vis) spectroscopy, Transmission Electron Microscope (TEM) and Dynamic Light Scattering (DLS) (Raid, 2013). Silver nanoparticles characterized as spherical shape, almost monodispersed at size of 1-20 nm. A preliminary study also performed in order to find out its suspected toxic effects, using different concentrations of Silver nanoparticles solutions on germination, vigour index and on the Fusarium oxysporium infection on the target crops. Silver nitrate solution or water treatment was used as positive and negative control respectively. Healthy and infected seeds were soaked in three different concentrations of Silver nanoparticles (0.5, 0.25 and 0.12 mM). At the higher concentration, silver nanoparticles alone or in combination with Fusarium spores showed adverse effect on seed germination and vigour index. The lower concentration of silver nanoparticles improved the seed germination percentage and vigour index, in addition to reduce the disease incidence (seed rot disease) caused by Fusarium oxysporium. The higher concentration of Silver nanoparticles 0.5 mM showed a slightly effects on seed germination percentage and vigour index in tomato seedlings. Silver nanoparticles at concentration of 0.12 mM were less toxic to the tomato, faba bean and barley seedlings. It also reduced the disease incidence. Therefore, it is recommended to consider Silver nanoparticles in further studies for possible controlling of seed-borne pathogens putting in mind its possible accumulation in the crop products and the consecutive in food chain.

https://jppp.journals.ekb.eg/article_87901_85a31139f3411d07d34ebd6bc30dc23c.pdf

Raida E. Al-Harbi

Papers

Biosynthesis and characterization of silver nanoparticles using Trichoderma longibrachiatum and their effect on phytopathogenic fungi

EFFECT OF BIOSYNTHESIZED SILVER NANOPARTICLES ON Fusarium oxysporum FUNGUS THE CAUSE OF SEED ROT DISEASE OF FABA BEAN, TOMATO AND BARLEY