Silver nanoparticles as a new generation of antimicrobials.

Here, we present a review of the antibacterial effects of silver nanomaterials, including proposed antibacterial mechanisms and possible toxicity to higher organisms. For purpose of this review, silver nanomaterials include silver nanoparticles, stabilized silver salts, silver–dendrimer, polymer and metal oxide composites, and silver-impregnated zeolite and activated carbon materials. While there is some evidence that silver nanoparticles can directly damage bacteria cell membranes, silver nanomaterials appear to exert bacteriocidal activity predominantly through release of silver ions followed (individually or in combination) by increased membrane permeability, loss of the proton motive force, inducing de-energization of the cells and efflux of phosphate, leakage of cellular content, and disruption DNA replication. Eukaryotic cells could be similarly impacted by most of these mechanisms and, indeed, a small but growing body of literature supports this concern. Most antimicrobial studies are performed in simple aquatic media or cell culture media without proper characterization of silver nanomaterial stability (aggregation, dissolution, and re-precipitation). Silver nanoparticle stability is governed by particle size, shape, and capping agents as well as solution pH, ionic strength, specific ions and ligands, and organic macromolecules—all of which influence silver nanoparticle stability and bioavailability. Although none of the studies reviewed definitively proved any immediate impacts to human health or the environment by a silver nanomaterial containing product, the entirety of the science reviewed suggests some caution and further research are warranted given the already widespread and rapidly growing use of silver nanomaterials.

https://link.springer.com/content/pdf/10.1007%2Fs11051-010-9900-y.pdf

A review of the antibacterial effects of silver nanomaterials and potential implications for human health and the environment

Green synthesis of metal nanoparticles using plants

/pdf/molecular-evolutionary-genetics-analysis-1uvpbl4lte.pdf

Molecular Evolutionary Genetics Analysis

Silver nanoparticles are nanoparticles of silver which are in the range of 1 and 100 nm in size. Silver nanoparticles have unique properties which help in molecular diagnostics, in therapies, as well as in devices that are used in several medical procedures. The major methods used for silver nanoparticle synthesis are the physical and chemical methods. The problem with the chemical and physical methods is that the synthesis is expensive and can also have toxic substances absorbed onto them. To overcome this, the biological method provides a feasible alternative. The major biological systems involved in this are bacteria, fungi, and plant extracts. The major applications of silver nanoparticles in the medical field include diagnostic applications and therapeutic applications. In most of the therapeutic applications, it is the antimicrobial property that is being majorly explored, though the anti-inflammatory property has its fair share of applications. Though silver nanoparticles are rampantly used in many medical procedures and devices as well as in various biological fields, they have their drawbacks due to nanotoxicity. This review provides a comprehensive view on the mechanism of action, production, applications in the medical field, and the health and environmental concerns that are allegedly caused due to these nanoparticles. The focus is on effective and efficient synthesis of silver nanoparticles while exploring their various prospective applications besides trying to understand the current scenario in the debates on the toxicity concerns these nanoparticles pose.

/pdf/silver-nanoparticles-mechanism-of-antimicrobial-action-3x1asgjbb2.pdf

Silver nanoparticles: mechanism of antimicrobial action, synthesis, medical applications, and toxicity effects

In the present scenario, pharmaceutical and biomedical sectors are facing the challenges of continuous increase in the multidrug-resistant (MDR) human pathogenic microbes. Re-emergence of MDR microbes is facilitated by drug and/or antibiotic resistance, which is acquired way of microbes for their survival and multiplication in uncomfortable environments. MDR bacterial infections lead to significant increase in mortality, morbidity and cost of prolonged treatments. Therefore, development, modification or searching the antimicrobial compounds having bactericidal potential against MDR bacteria is a priority area of research. Silver in the form of various compounds and bhasmas have been used in Ayurveda to treat several bacterial infections since time immemorial. As several pathogenic bacteria are developing antibiotic resistance, silver nanoparticles are the new hope to treat them. This review discusses the bactericidal potential of silver nanoparticles against the MDR bacteria. This multiactional nanoweapon can be used for the treatment and prevention of drug-resistant microbes.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1365-2672.2012.05253.x

Silver nanoparticles: the powerful nanoweapon against multidrug-resistant bacteria

Fungus-mediated synthesis of silver nanoparticles and their activity against pathogenic fungi in combination with fluconazole

We report extracellular mycosynthesis of silver nanoparticles by Fusarium acuminatum Ell. and Ev. (USM-3793) isolated from infected ginger (Zingiber officinale). An aqueous silver nitrate solution was reduced to metallic silver when exposed to F. acumi- natum cell extract leading to the appearance of a brown color within 15-20 minutes. The color is due to the formation of silver nanoparti- cles and the excitation of surface plasmons. The optical spectrum showed the plasmon resonance at 420 nm and analysis by transmission electron microscopy confirmed the presence of silver nanoparticles. The nanoparticles produced were spherical with a broad size distribu- tion in the range of 5-40 nm with average diameter of 13 nm. The reduction of the silver ions occurs probably by a nitrate-dependent re- ductase enzyme, which we found to be present in the extra-cellular medium. We tested the silver particles for their broad-band antibacte- rial activity on different human pathogens. We observed efficient antibacterial activity against multidrug resistant and highly pathogenic bacteria, including multidrug resistant Staphylococcus aureus, Salmonella typhi, Staphylococcus epidermidis, and Escherichia coli. The synthesis of silver nanoparticles by the fungus F. acuminatum may therefore serve as a simple, cheap, eco-friendly, reliable and safe method to produce an antimicrobial material.

Mycosynthesis of Silver Nanoparticles Using the Fungus Fusarium acuminatum and its Activity Against Some Human Pathogenic Bacteria

Nanotechnology is a promising field of interdisciplinary research. It opens up a wide array of opportunities in various fields like medicine, pharmaceuticals, electronics and agriculture. The potential uses and benefits of nanotechnology are enormous. These include insect pests management through the formulations of nanomaterials-based pesticides and insecticides, enhancement of agricultural productivity using bio-conjugated nanoparticles (encapsulation) for slow release of nutrients and water, nanoparticle-mediated gene or DNA transfer in plants for the development of insect pest-resistant varieties and use of nanomaterials for preparation of different kind of biosensors, which would be useful in remote sensing devices required for precision farming. Traditional strategies like integrated pest management used in agriculture are insufficient, and application of chemical pesticides like DDT have adverse effects on animals and human beings apart from the decline in soil fertility. Therefore, nanotechnology would provide green and efficient alternatives for the management of insect pests in agriculture without harming the nature. This review is focused on traditional strategies used for the management of insect pests, limitations of use of chemical pesticides and potential of nanomaterials in insect pest management as modern approaches of nanotechnology.

Avinash P. Ingle

Papers

Silver nanoparticles: the powerful nanoweapon against multidrug-resistant bacteria

Fungus-mediated synthesis of silver nanoparticles and their activity against pathogenic fungi in combination with fluconazole

Mycosynthesis of Silver Nanoparticles Using the Fungus Fusarium acuminatum and its Activity Against Some Human Pathogenic Bacteria

Role of nanotechnology in agriculture with special reference to management of insect pests

Exploitation of Aspergillus niger for Synthesis of Silver Nanoparticles