These approaches carry health and environmental disadvantages with themselves. Need for safer alternatives in large-scale production of NPs ended up with development of eco-friendly methods. Industrial nanobiotechnology takes advantage of biological-based approaches to produce nanomaterial using biological renewable resources.
Decreasing energy intake, greenhouse gas GHG , and hazardous waste production are the main advantages of nanomaterial biosynthesis.
Green biosynthesis of nanoparticles: mechanisms and applications.
In contrast, the other synthesis methods bring environmental drawbacks. Among the nanomaterials, nanoparticles have attracted the attention because of their wide spectrum of application. Microorganisms and in particular bacteria and fungi are used as the biological agents and showed a promising potential for biosynthesis of nanoparticles.
Here we highlight different aspects of industrial production of NPs by fungi including advantages and disadvantages.
Also, we discuss the application of different technologies in development of high-scale production of NPs by fungi-like protein engineering, metabolic engineering, synthetic biology, systems biology, and downstream processing. Skip to main content.
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Nanomedicine — CrossRef Google Scholar. Hiramatsu H, Osterloh FE A simple large-scale synthesis of nearly monodisperse gold and silver nanoparticles with adjustable sizes and with exchangeable surfactants. Iravani S Bacteria in nanoparticle synthesis: current status and future prospects. Nevoigt E Progress in metabolic engineering of Saccharomyces cerevisiae. Science — CrossRef Google Scholar. Picataggio S Potential impact of synthetic biology on the development of microbial systems for the production of renewable fuels and chemicals. Fungi have been observed as good producers of silver nanoparticles due to their tolerance and capability of bioaccumulation of metals.
Many reports dealing with biosynthesis of silver nanoparticles using fungi or yeasts have been published.
For example, fungus-mediated synthesis of silver nanoparticles was described by Mukherjee [ 57 ]. Extracellular production of silver nanoparticles was described, for example, by Sadowski, who prepared nanoparticles from Penicillium fungi isolated from the soil [ 58 ]. The discovery of the first antibiotics has dramatically changed the quality of human life, but the development of the natural mechanism of bacterial resistance has been forced scientists to develop more effective antimicrobial drugs.
The interest about the use of nanoparticles as antibacterial agents has seen a dramatic increase in the last few decades. The unique properties of silver nanoparticles have allowed exploiting in medicinal field. The most studies have been attended to their antimicrobial nature. Since silver nanoparticles show promising antimicrobial activity, researchers use several techniques to determine and quantify their activity on various Gram-positive and Gram-negative bacteria.
To evaluate the antimicrobial activity different methods are currently used, the results of which are given in different ways. Commonly used techniques to determine the antimicrobial activity of biogenic silver are the minimal inhibitory concentration MIC , the minimal bactericidal concentration MBC , time-kill, the half effective concentration EC 50 , well-diffusion method, and disc-diffusion method.
The most commonly used is disc-diffusion method developed in These well-known procedures are comprised of preparation of agar plates incubated with a standardized inoculum of test microorganism. Cultured agar plates are incubated under conditions suitable for tested bacteria, and the sensitivity of the tested organisms to the AgNPs is determined by measuring the diameter of the zone of inhibition around the disc or well. This method is contributed and beneficial for its simplicity and low cost and is commonly used in antibacterial activity of Ag nanoparticles evaluation [ 59 ].
The antibacterial properties of silver nanoparticles are often studied by employing dilution methods, quantitative assays, the most appropriate ones for the determination of MIC values. Either broth or agar dilution method may be used for quantitative measurement, the in vitro antimicrobial activity against bacteria. The minimum bactericidal concentration MBC is less common compared to MIC determination and is defined as the lowest concentration of antimicrobial agent killing The most appropriate method for determining the bactericidal effect is the time-kill test and can be also used to determine synergism for combination of two or more antimicrobial agents.
These tests provide information about the dynamic interaction between different strains of microorganism and antimicrobial agents.
Green Biosynthesis of Nanoparticles: Mechanisms and Applications
The time-kill test reveals a time-dependent or a concentration-dependent antimicrobial effect. The varied time intervals of incubation are used usually 0, 4, 6, 8, 10, 12, and 24 h , and the resulting data for the test are typically presented graphically [ 59 ]. Antimicrobial activity of silver is well known. Silver has been used for treatment of several diseases since from ancient time [ 60 ]. The AgNPs synthesized by different methods were widely tested against number of pathogenic bacteria with evidence of strong antimicrobial activity against a broad-spectrum bacteria including both Gram-negative and Gram-positive.
Some researchers have been reported that the AgNPs are more effective against Gram-negative bacteria [ 61 , 62 , 63 ], while opposite results have also been found [ 64 ]. The difference in sensitivity of Gram-positive and Gram-negative bacteria against AgNPs may result from the variation in the thickness and molecular composition of the membranes. Gram-positive bacteria cell wall composed of peptidoglycan is comparatively much thicker than that of Gram-negative bacteria [ 2 , 65 ].
The importance of antibacterial activity study on different bacterial strains becomes from the importance of understanding the mechanism, resistance and future application. Although the antibacterial effect of silver nanoparticles has been widely studied, there are some factors affecting the antimicrobial properties of AgNPs, such as shape, size, and concentration of nanoparticles and capping agents [ 30 ].
These nanoparticles showed excellent antibacterial activity in P. The smaller particles with a larger surface-to-volume ratio were able to reach bacterial proximity most easily and display the highest microbicidal effects than larger particles [ 19 , 69 , 76 ]. Normally, a high concentration leads to more effective antimicrobial activity, but particles of small sizes can kill bacteria at a lower concentration. Furthermore, apart from size and concentration, shape also influences the interaction with the Gram-negative organism E.
They found that observed interaction between nanoparticles of silver with various shapes and E. They speculated about the fact that AgNPs with the same surface areas, but different shapes, may have unequal effective surface areas in terms of active facets [ 78 ]. SEM analysis indicated that both strains were damaged and extensively inhibited by Ag-nanoplates due to the increasing surface area in AgNPs.
In the past decade, silver nanoparticles as antimicrobial agents have attracted much attention in the scientific field. Most studies considered multiple mechanisms of action but simplified the main tree of different mechanisms determine the antimicrobial activity of silver nanoparticles: 1 irreversible damage of bacterial cell membrane through direct contact; 2 generation of reactive oxygen species ROS ; and 3 interaction with DNA and proteins [ 80 , 81 , 82 , 83 ].
The damage of cell membranes by AgNPs causing structural changes renders bacteria more permeable and disturbs respiration function [ 84 ]. Several evidences suggest that the silver ions are important in the antimicrobial activity of silver nanoparticles [ 81 , 85 ]. On the other side, silver ion can interact with the thiol groups of many vital enzymes and inactivate them and generate reactive oxygen species ROS [ 29 ]. The AgNPs can act as a reservoir for the monovalent silver species released in the presence of an oxidizer. A novel mechanism for the antibacterial effect of silver nanoparticles, namely the induction of a bacterial apoptosis-like response, was described.
Antimicrobial activity of silver nanoparticles combined with various antibiotics is currently being studied, and the synergistic antibacterial effect has been found. They found that synergistic action of AgNPs and antibiotics resulted in enhanced antibacterial effect. Exposure of bacteria in combination of AgNPs and antibiotics reduced the MICs significantly, and the bacteria were found to be susceptible to all of the tested antibiotics, except cephalosporins, where no change was observed.
The significant reduction of required antibiotic dose up to fold in combination with small amount of AgNPs could achieve the same effect. Briefly, simultaneous action of AgNPs with antibiotics could prevent the development of bacterial resistance. These results are in accordance with findings reported by Gurunathan [ 76 ], who observed synergistic effects of silver nanoparticles in the presence of conventional antibiotics on Gram-negative bacteria E. The resistance on antibiotic treatment of S.
These triple combinations of blue light, AgNPs, and the antibiotic considerably enhanced the antimicrobial activity against MRSA, in comparison with treatments involving one or two agents. The biofilm formation is adjunctive problem of resistance on antimicrobial agents and chronic bacterial infections. It was proposed that Ag-NPs can impede biofilm formation [ 89 ]. The antibiotics enoxacin, kanamycin, neomycin, and tetracycline interact with AgNPs strongly and forming antibiotic-AgNPs complex, while no such effects were observed for ampicillin and penicillin.
The use of silver nanoparticles provides an opportunity to solve a global problem of bacterial resistance toward antibiotics. The possibilities of silver nanoparticles synthesis are very broad. In the last decade, there has been dramatically grown scientific interest in nanoparticles biosynthesis by various reducing and capping agents presented in biological sources including plants, plant extracts, microorganism, or larvae.
The natural green synthesis approach is an eco-friendly and cost-effective due to the fact that no toxic and dangerous chemicals are used. One of the key aspect in the design of more potent antibacterial system is the understanding its mode of action. Generally, nanoparticles are well established as promising alternative to antibiotic therapy or combinational therapy because they possess unbelievable potential for solving the problem with the development of pathogens resistance.
Finally, from this point of view, silver nanoparticles represent product with potential application in medicine and hygiene, and the green synthesis of AgNPs can pave a way for the same. Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution 3. Help us write another book on this subject and reach those readers. Login to your personal dashboard for more detailed statistics on your publications.
We are IntechOpen, the world's leading publisher of Open Access books. Built by scientists, for scientists. Our readership spans scientists, professors, researchers, librarians, and students, as well as business professionals. Downloaded: Abstract The prevalence of infectious diseases is becoming a worldwide problem, and antimicrobial drugs have long been used for prophylactic and therapeutic purposes, but bacterial resistance has creating serious treatment problems.
Green Biosynthesis of Nanoparticles: Mechanisms and Applications
Keywords silver nanoparticles plant extracts antibacterial activity green synthesis biosynthesis. Introduction Frequent use of antibiotics results in resistance of pathogens against them. Synthesis of silver nanoparticles Production of nanoparticles can be achieved through different methods. Physical and chemical methods For a physical approach, the nanoparticles are prepared using evaporation-condensation, which could be carried out in a tube furnace at atmospheric pressure [ 16 ].
Green synthesis As we described, there are various chemical and physical methods of synthesis of silver nanoparticles. Silver nanoparticles synthesis Physical methods Chemical methods Green synthesis methods In vitro methods In vivo methods Pulsed laser ablation Evaporation-condensation Spray pyrolysis Ball milling Vapor and gas phase Arc discharge Reduction Sonochemical Photochemical Electrochemical Microwave Using microorganisms Using plant extracts Using biomolecules Using algae Using mushroom extracts Using essential oils Using plant Using microorganisms Using yeast Using algae.
Selected techniques for the preparation of AgNPs. Tested bacteria Method Ref. G-: E. Cell-free extract 0. Green synthesized AgNPs and their antibacterial activity, if determined. In vitro synthesis of AgNPs In the so-called green approach, the reduction procedure is performed by a natural-based material, most commonly a plant extract containing substances with the antioxidant and reducing properties, e. In vivo synthesis of AgNPs Under the term in vivo , we understand the biosynthesis of nanoparticles in living organisms, either extracts or isolated biomolecules.
Antibacterial activity The discovery of the first antibiotics has dramatically changed the quality of human life, but the development of the natural mechanism of bacterial resistance has been forced scientists to develop more effective antimicrobial drugs. Methods of evaluation of antibacterial activity To evaluate the antimicrobial activity different methods are currently used, the results of which are given in different ways.
Antibacterial activity of AgNPs Antimicrobial activity of silver is well known. Mechanism of action In the past decade, silver nanoparticles as antimicrobial agents have attracted much attention in the scientific field. Conclusion The use of silver nanoparticles provides an opportunity to solve a global problem of bacterial resistance toward antibiotics.
Conflict of interest The authors declare no conflict of interest.
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