Despite numerous existing potent antibiotics and other antimicrobial means, bacterial infections are still a major cause of morbidity and mortality. Moreover, the need to develop additional bactericidal means has significantly increased due to the growing concern regarding multidrug-resistant bacterial strains and biofilm associated infections. Consequently, attention has been especially devoted to new and emerging nanoparticle-based materials in the field of antimicrobial chemotherapy. The present review discusses the activities of nanoparticles as an antimicrobial means, their mode of action, nanoparticle effect on drug-resistant bacteria, and the risks attendant on their use as antibacterial agents. Factors contributing to nanoparticle performance in the clinical setting, their unique properties, and mechanism of action as antibacterial agents are discussed in detail.

/pdf/alternative-antimicrobial-approach-nano-antimicrobial-fcpo20i2qt.pdf

Alternative Antimicrobial Approach: Nano-Antimicrobial Materials

Since discovery of the first antibiotic drug, penicillin, in 1928, a variety of antibiotic and antimicrobial agents have been developed and used for both human therapy and industrial applications. However, excess and uncontrolled use of antibiotic agents has caused a significant growth in the number of drug resistant pathogens. Novel therapeutic approaches replacing the inefficient antibiotics are in high demand to overcome increasing microbial multidrug resistance. In the recent years, ongoing research has focused on development of nano-scale objects as efficient antimicrobial therapies. Among the various nanoparticles, silver nanoparticles have gained much attention due to their unique antimicrobial properties. However, concerns about the synthesis of these materials such as use of precursor chemicals and toxic solvents, and generation of toxic byproducts have led to a new alternative approach, green synthesis. This eco-friendly technique incorporates use of biological agents, plants or microbial agents as reducing and capping agents. Silver nanoparticles synthesized by green chemistry offer a novel and potential alternative to chemically synthesized nanoparticles. In this review, we discuss the recent advances in green synthesis of silver nanoparticles, their application as antimicrobial agents and mechanism of antimicrobial mode of action.

https://pubs.rsc.org/en/content/articlepdf/2019/ra/c8ra08982e

Green synthesis of silver nanoparticles: biomolecule-nanoparticle organizations targeting antimicrobial activity

Development of reliable and eco-accommodating methods for the synthesis of nanoparticles is a vital step in the field of nanotechnology. Silver nanoparticles are important because of their exceptional chemical, physical, and biological properties, and hence applications. In the last decade, numerous efforts were made to develop green methods of synthesis to avoid the hazardous byproducts. This review describes the methods of green synthesis for Ag-NPs and their numerous applications. It also describes the comparison of efficient synthesis methods via green routes over physical and chemical methods, which provide strong evidence for the selection of suitable method for the synthesis of Ag-NPs.

A review on green synthesis of silver nanoparticles and their applications

Metal nanoparticles have received great attention from researchers across the world because of a plethora of applications in agriculture and the biomedical field as antioxidants and antimicrobial compounds. Over the past few years, green nanotechnology has emerged as a significant approach for the synthesis and fabrication of metal nanoparticles. This green route employs various reducing and stabilizing agents from biological resources for the synthesis of nanoparticles. The present article aims to review the progress made in recent years on nanoparticle biosynthesis by microbes. These microbial resources include bacteria, fungi, yeast, algae and viruses. This review mainly focuses on the biosynthesis of the most commonly studied metal and metal salt nanoparticles such as silver, gold, platinum, palladium, copper, cadmium, titanium oxide, zinc oxide and cadmium sulphide. These nanoparticles can be used in pharmaceutical products as antimicrobial and anti-biofilm agents, targeted delivery of anticancer drugs, water electrolysis, waste water treatment, biosensors, biocatalysis, crop protection against pathogens, degradation of dyes etc. This review will discuss in detail various microbial modes of nanoparticles synthesis and the mechanism of their synthesis by various bioreducing agents such as enzymes, peptides, proteins, electron shuttle quinones and exopolysaccharides. A thorough understanding of the molecular mechanism of biosynthesis is the need of the hour to develop a technology for large scale production of bio-mediated nanoparticles. The present review also discusses the advantages of various microbial approaches in nanoparticles synthesis and lacuna involved in such processes. This review also highlights the recent milestones achieved on large scale production and future perspectives of nanoparticles.

/pdf/a-review-on-the-biosynthesis-of-metal-and-metal-salt-397h4p77mi.pdf

A review on the biosynthesis of metal and metal salt nanoparticles by microbes

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.

/pdf/synthesis-of-silver-nanoparticles-mediated-by-fungi-a-review-43fu174r7e.pdf

Synthesis of Silver Nanoparticles Mediated by Fungi: A Review.

Development of ecofriendly and reliable processes for the synthesis of nanoparticles has attracted considerable interest in nanotechnology because of its tremendous impetus in modulating metals into nanosize to their potential use for human benefits. In this study an endophytic fungus, Penicillium sp., isolated from healthy leaves of Curcuma longa (turmeric) was subjected to extracellular biosynthesis of silver nanoparticles (AgNps) and their activity against MDR E. coli and S. aureus. The biosynthesized AgNps optimization was studied and characterized by UV-visible spectroscopy, Fourier transform infrared spectroscopy (FTIR), and transmission electron microscopy (TEM). Then produced AgNps were tested against MDR E. coli and S. aureus. The endophytic fungus Penicillium sp. from healthy leaves of C. longa (turmeric) was found to be a good producer of AgNps. Parametric optimization showed maximum absorbance of 420–425 nm at pH-7, 25°C with 1 mM AgNO3 concentration and 15–20 g of wet biomass. Further TEM revealed the formation of spherical, well-dispersed nanoparticles with size ranging between 25 and 30 nm and FTIR shows the bands at 1644 and 1538 cm−1 corresponding to the binding vibrations of amide I and II bands of proteins, respectively. Antibacterial activity against MDR E. coli and S. aureus showed good results showing maximum zone of inhibition of 17 mm and 16 mm, respectively, at 80 µL of AgNps.

/pdf/optimization-and-characterization-of-silver-nanoparticle-by-1rb2siihqi.pdf

Optimization and Characterization of Silver Nanoparticle by Endophytic Fungi Penicillium sp. Isolated from Curcuma longa (Turmeric) and Application Studies against MDR E. coli and S. aureus

Silver Nanoparticles (AgNPs), the real silver bullet, are known to have good antibacterial properties against pathogenic microorganisms. In the present study AgNPs were prepared from extracellular filtrate of Aspergillus niger. Characterization of AgNPs by UV-Vis spectrum reveals specific surface plasmon resonance at peak 416 nm; TEM photographs revealed the size of the AgNPs to be 20–55 nm. Average diameter of the produced AgNPs was found to be 73 nm with a zeta potential that was −24 mV using Malvern Zetasizer. SEM micrographs showed AgNPs to be spherical with smooth morphology. EDS revealed the presence of pure metallic AgNPs along with carbon and oxygen signatures. Of the different concentrations (0, 2.5, 5, 10, and 15 μg/mL) used 10 μg/mL were sufficient to inhibit 107 CFU/mL of E. coli. ROS production was measured using DCFH-DA method and the the free radical generation effect of AgNPs on bacterial growth inhibition was investigated by ESR spectroscopy. This paper not only deals with the damage inflicted on microorganisms by AgNPs but also induces cell death through the production of ROS released by AgNPs and also growth kinetics of E. coli supplemented with AgNPs produced by A. niger.

/pdf/growth-kinetics-and-mechanistic-action-of-reactive-oxygen-45s261i2jn.pdf

Growth kinetics and mechanistic action of reactive oxygen species released by silver nanoparticles from Aspergillus niger on Escherichia coli.

Nanotechnology has become a platform to alter and modify and develop the important properties of metal in the form of nanopaticles with its promising applications in various fields for the benefit of mankind. In the present study endophytic fungus Fusarium sp. was isolated from healthy leaves of Withania sominnifera (Ashwagandha) and was subjected for the extracellular biosynthesis of silver nanoparticles (AgNps). The synthesized AgNps were characterized using visual observation, UV-Vis spectroscopy and Transmission Electron Microscopy (TEM). Further AgNps synthesized were tested for their efficacy against the bacterial pathogens like E.coli, S.typhi and S.aureus. The formation of AgNps was confirmed by visual observation by change in colour from pale white to brown and the Surface Plasmon Resonance was determined by UV-Vis spectra at 422 nm. TEM revealed the formation of small sized spherical shaped nanoparticles ranging 12-20 nm. Antibacterial activity of AgNps against E.coli, S.typhi and S.aureus showed encouraging results, showing maximum zone of inhibition of 26mm, 26mm and 28 mm respectively at 60µl concentration of AgNps against E.coli, S.typhi and S.aureus.

Original Article Bioactive Silver Nanoparticles from Endophytic Fungus Fusarium sp. Isolated from an Ethanomedicinal Plant Withania somnifera (Ashwagandha) and its Antibacterial Activity

AgNps were synthesized from the Endophytic fungus Fusarium semitectum isolated from healthy leaves of a medicinal plant Withania somnifera (Ashwagandha). Characterization of AgNps by UV-Vis showed a maximum absorption peak at 422nm. TEM revealed AgNps to be smaller in size, spherical in shape from 1220nm. Different concentration of AgNps was tested against germination of Mungbean, Pigeon Pea and Chickpea seeds. Percent seed germination, root and shoot length of all the three seeds were measured. The Germination index (G.I) of Mungbean and Pigeon Pea seeds was maximum 123.33 and 117.64 with 200μl of AgNps and Cent percent seed germination in Mungbean seeds while it was 58.3% in Pigeon Pea. The average root and shoot length was maximum 4.6cm and 4.7cm with 100μl of AgNps in Mungbean whereas, shoot length was 4cm at 200μl and root length was 4.4cm at 100μl. In case of Chickpea the G.I was maximum 46.51 with maximum % seed germination of 78.5% and shoot length of 2cm with maximum root length of 4.9cm at 100μl of AgNps. All these results reveal that 100 and 200μl of AgNps can enhance root and shoot germination while, higher concentration of AgNps showed Phytotoxicity revealing that dose dependency will have good effect on overall plant growth.

/pdf/effect-of-silver-nanoparticles-agnps-produced-by-an-4a60pxmzzk.pdf

Effect of Silver Nanoparticles (AgNps) Produced by an Endophytic Fungus Fusarium Semitectum Isolated from a Medicinal Plant Withania Somnifera (Ashwagandha) on Seed Germination

Jasmine Mathew

Papers

Optimization and Characterization of Silver Nanoparticle by Endophytic Fungi Penicillium sp. Isolated from Curcuma longa (Turmeric) and Application Studies against MDR E. coli and S. aureus

Growth kinetics and mechanistic action of reactive oxygen species released by silver nanoparticles from Aspergillus niger on Escherichia coli.

Original Article Bioactive Silver Nanoparticles from Endophytic Fungus Fusarium sp. Isolated from an Ethanomedicinal Plant Withania somnifera (Ashwagandha) and its Antibacterial Activity

Effect of Silver Nanoparticles (AgNps) Produced by an Endophytic Fungus Fusarium Semitectum Isolated from a Medicinal Plant Withania Somnifera (Ashwagandha) on Seed Germination

Enhanced efficacy of Ketoconazole coated silver nanoparticles against the fungus Malassezia furfur: a dandruff causing agent.