Nanotechnology is the creation, manipulation and use of materials at the nanometre size scale (1 to 100 nm). At this size scale there are significant differences in many material properties that are normally not seen in the same materials at larger scales. Although nanoscale materials can be produced using a variety of traditional physical and chemical processes, it is now possible to biologically synthesize materials via environment-friendly green chemistry based techniques. In recent years, the convergence between nanotechnology and biology has created the new field of nanobiotechnology that incorporates the use of biological entities such as actinomycetes algae, bacteria, fungi, viruses, yeasts, and plants in a number of biochemical and biophysical processes. The biological synthesis via nanobiotechnology processes have a significant potential to boost nanoparticles production without the use of harsh, toxic, and expensive chemicals commonly used in conventional physical and chemical processes. The aim of this review is to provide an overview of recent trends in synthesizing nanoparticles via biological entities and their potential applications.

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Green Synthesis of Metallic Nanoparticles via Biological Entities

Silver Nanoparticles: Therapeutical Uses, Toxicity, and Safety Issues

Silver nanoparticles (AgNPs) have received tremendous attention due to their significant antimicrobial properties. Large numbers of reports are available on the physical, chemical, and biological syntheses of colloidal AgNPs. Since there is a great need to develop ecofriendly and sustainable methods, biological systems like bacteria, fungi, and plants are being employed to synthesize these nanoparticles. The present review focuses specifically on bacteria-mediated synthesis of AgNPs, its mechanism, and applications. Bacterial synthesis of extra- and intracellular AgNPs has been reported using biomass, supernatant, cell-free extract, and derived components. The extracellular mode of synthesis is preferred over the intracellular mode owing to easy recovery of nanoparticles. Silver-resistant genes, c-type cytochromes, peptides, cellular enzymes like nitrate reductase, and reducing cofactors play significant roles in AgNP synthesis in bacteria. Organic materials released by bacteria act as natural capping and stabilizing agents for AgNPs, thereby preventing their aggregation and providing stability for a longer time. Regulation over reaction conditions has been suggested to control the morphology, dispersion, and yield of nanoparticles. Bacterial AgNPs have anticancer and antioxidant properties. Moreover, the antimicrobial activity of AgNPs in combination with antibiotics signifies their importance in combating the multidrug-resistant pathogenic microorganisms. Multiple microbicidal mechanisms exhibited by AgNPs, depending upon their size and shape, make them very promising as novel nanoantibiotics.

Bacteriagenic silver nanoparticles: synthesis, mechanism, and applications.

https://digitalcommons.fiu.edu/cgi/viewcontent.cgi?article=1181&context=cas_bio

Screening of cyanobacteria and microalgae for their ability to synthesize silver nanoparticles with antibacterial activity.

The green synthesis (GS) of different metallic nanoparticles (MNPs) has re-evaluated plants, animals and microorganisms for their natural potential to reduce metallic ions into neutral atoms at no expense of toxic and hazardous chemicals. Contrary to chemically synthesized MNPs, GS offers advantages of enhanced biocompatibility and thus has better scope for biomedical applications. Plant, animals and microorganisms belonging to lower and higher taxonomic groups have been experimented for GS of MNPs, such as gold (Au), silver (Ag), copper oxide (CuO), zinc oxide (ZnO), iron (Fe2O3), palladium (Pd), platinum (Pt), nickel oxide (NiO) and magnesium oxide (MgO). Among the different plant groups used for GS, angiosperms and algae have been explored the most with great success. GS with animal-derived biomaterials, such as chitin, silk (sericin, fibroin and spider silk) or cell extract of invertebrates have also been reported. Gram positive and gram negative bacteria, different fungal species and virus particles have also shown their abilities in the reduction of metal ions. However, not a thumb rule, most of the reducing agents sourced from living world also act as capping agents and render MNPs less toxic or more biocompatible. The most unexplored area so far in GS is the mechanism studies for different natural reducing agents expect for few of them, such as tea and neem plants. This review encompasses the recent advances in the GS of MNPs using plants, animals and microorganisms and analyzes the key points and further discusses the pros and cons of GS in respect of chemical synthesis.

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Biological synthesis of metallic nanoparticles: plants, animals and microbial aspects

Silver nanoparticles is known to have antimicrobial affects Cyanobacteria isolates from muthupet mangrove includes Aphanothece sp, Oscillatoria sp, Microcoleus sp, Aphanocapsa sp, Phormidium sp, Lyngbya sp, Gleocapsa sp, Synechococcus sp, Spirulina sp with were set in compliance with their cellular mechanism of nano silver creation, and were investigated by UV-VIS spectrophotometer, Energy-dispersive X-ray (EDX) and scanning electron microscopy (SEM) Silver nanoparticles were spherical shaped well distributed without aggregation in solution with an average size of about 40- 80 nm Synthesised nano silver had antibacterial production on various organisms that provoked various diseases in humans The cellular metabolites of Microcoleus sp only created nano silver and it enhanced the antibacterial activity against test pathogenic bacteria from MTCC (Proteus vulgaris, Salmonella typhi, Vibrio cholera, Streptococcus sp, Bacillus subtilis, Staphylococcus aureus, Escherichia coli) The antimicrobial assay was performed using 0001 M concentration of nano silver in well diffusion method with positive control of appropriate standard antibiotic discs Cephotaxime, Ampicillin, Tetracyclin, Cephalexin etc Synthesised silver nanoparticles acted as an effective antimicrobial agent and proved as an alternative for the development of new antimicrobial agents to combat the problem of resistance

http://nopr.niscair.res.in/bitstream/123456789/17672/1/IJEB%2051%285%29%20393-399.pdf

Microalgae mediated synthesis of silver nanoparticles and their antibacterial activity against pathogenic bacteria.

Microalgae associated Brevundimonas sp. MSK 4 as the nano particle synthesizing unit to produce antimicrobial silver nanoparticles.

The screening of antioxidant and antimicrobial potentiality of Spirulina platensis and Aphanothece sp against multidrug resistant pathogens were investigated using standard microbiological techniques and antioxidant is determined by FRAP and DPPH. The intracellular and extra cellular extracts were tested by agar well diffusion method for activity against Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, Klebsiella sp, Proteus sp and Embedobacter sp. isolated from clinical samples. The susceptibility patterns of the test isolates against the extract intracellular and extra cellular was determined. The result showed that no significant antibacterial activity by Aphanothece sp, in contrast intracellular extracts of S.platensis produce antibacterial activity against above mentioned strains and S.platensis have more antioxidant activity than Aphanothece sp. The observed antibacterial effects were believed to be due to the presence of alkaloids, tannins, and flavonoids identified in the extracts. The results apparently justified their use in the treatment of infections.

Antimicrobial activity of Spirulina platensis and Aphanothece sp. on selected clinical bacterial isolates and its Antioxidant activity

Cyanobacteria are known to be colonized by various heterotrophic bacteria. With a view to understand the associated organisms from cyanobacterial products especially 6 different Spirulina products such as two forms of Spirulina powder, one crunchy form and three different tablets were selected. A total of 30 bacterial strains were isolated and their biochemical and cultural characteristics were studied. The isolates were subjected for silver nanoparticle production. Microscopic results revealed that most of them were gram positive and non-motile. Among the 30 isolates most of them can able to synthesize nanoparticles with silver. It indicates that the colonial characteristics alone cannot serve as a tool to characterize the bacterial isolates. Hence these isolates were carefully examined and selected for further analysis.

J. Rengaramanujam

Papers

Microalgae mediated synthesis of silver nanoparticles and their antibacterial activity against pathogenic bacteria.

Microalgae associated Brevundimonas sp. MSK 4 as the nano particle synthesizing unit to produce antimicrobial silver nanoparticles.

Antimicrobial activity of Spirulina platensis and Aphanothece sp. on selected clinical bacterial isolates and its Antioxidant activity

Isolation and preliminary characterization of associated microoorganisms from spirulina products and their silver mediated nanoparticle synthesis