
In the recent years, noble nanoparticles have attracted and emerged in the field of biology, medicine and electronics due to their incredible applications. There were several methods have been used for synthesis of nanoparticles such as toxic chemicals and high energy physical procedures. To overcome these, biological method has been used for the synthesis of various metal nanoparticles. Among the nanoparticles, silver nanoparticles (AgNPs) have received much attention in various fields, such as antimicrobial activity, therapeutics, bio-molecular detection, silver nanocoated medical devices and optical receptor. Moreover, the biological approach, in particular the usage of natural organisms has offered a reliable, simple, nontoxic and environmental friendly method. Hence, the current article is focused on the biological synthesis of silver nanoparticles and their application in the biomedical field.
The study of nanomaterial has been emerging dramatically throughout the world in the 21st century due to their incredible applications in all spheres of human life (1). It has opened several arms in the development of new nanomaterials and examining their properties by tuning the particle size, shape and distribution (2,3). Metal nanoparticles have been extensively studied due to their specific characteristics such as catalytic activity, optical properties, electronic properties, antimicrobial properties and magnetic properties (4). Traditionally UV irradiation, aerosol technologies, lithography, laser ablation, ultrasonic fields, and photochemical reduction techniques have been used successfully to produce various metal nanoparticles such as gold, silver, platinum and palladium. However, considering the fast growth in the usage of nanomaterials in diverse fields, there is an urgent need to develop clean, nontoxic, simple and eco-friendly procedures for their synthesis.
Synthesis of noble metal nanoparticles, in particular silver nanoparticles (AgNPs) synthesis using natural organism has become a major research area in the field of nanotechnology. This may due to their simplicity of procedures, stability of nanoparticles, and their potential applications in chemical sensing, biological imaging, antimicrobial, gene silencing, drug delivery (5). Recently, several studies have reported natural polymers such as chitosan, starch and tannic acid as reducing agents for the synthesis of silver and gold nanoparticles (6,7). A vast array of biological resources including plants, algae, fungi, yeast, bacteria, and viruses has been studied so far for the intra and extracellular synthesis of silver, gold, platinum and titanium nanoparticles in different sizes and shapes were tabulated in Table 1. The major drawback of metal nanoparticles synthesis using plant extracts as reducing and stabilizing agent. This differs due to significant variation of biochemical compositions present in the plant extract of the same species differ from other part of the world. Therefore, identifying the biomolecules responsible for mediating the nanoparticles synthesis is a problem to overcome (8).
Soil is an extensively explored ecological niche for sources of microorganisms that are involved in various interactions. Among these, Metal-microbe interactions have important roles with fascinating applications such as bioremediation, biomineralization, bioleaching and microbial corrosion. However, recently that microorganisms have been explored as potential biofactory for synthesis of metallic nanoparticles such as cadmium, gold and silver (9,10). Among the microbes, the use of bacteria, like in this study, is rapidly gaining importance due to its growing success, ease of handling and genetic modification. Klaus
Viruses are unicellular organisms that hijack the replication machinery of the host cell and suspend most endogenous cellular activity. Their structure consists of nucleic acid, either DNA or RNA, which is surrounded by a protein shell that may or may not contain a lipid envelope. Viral genomes can be non-segmented, consisting of a single nucleic acid molecule, or segmented, consisting of more than one nucleic acid molecule. The nucleic acid molecules of a virus can be contained within a single virus or separated into multiple viruses. Viruses do not express their own ribosomal RNA. Viruses hold great promise in assembling and interconnecting novel nanosized components, allowing developing organized nanoparticle assemblies. Due to their size, monodispersity, and variety of chemical groups available for modification, they make a good scaffold for molecular assembly into nanoscale devices. Virus based nanocomposites are useful as an engineering material for the construction of smart nano-objects because of their ability to associate into desired structures including a number of morphologies. Viruses exhibit the characteristics of an ideal template for the formation of nano-conjugates with noble metal nanoparticles.
These bioinspired systems form monodispersed units that are highly amenable through genetic and chemical modifications. As nanoscale assemblies, viruses have sophisticated yet highly ordered structural features, which, in many cases, have been carefully characterized by modern structural biological methods. For many years animal viruses have been developed for material science, gene delivery and gene therapy purposes. More recently, other pathogens such as plant viruses, bacteriophages and viruses are increasingly being used for nanobiotechnology purposes because of their relative structural and chemical stability, ease of production, and lack of toxicity and pathogenicity in animals or humans (14). Biological scaffolds (viruses) hold great promise in assembling and interconnecting novel nanosized components, allowing such organized assemblies to interface with well-developed technologies such as lithography as nanotechnology develops (15). The cowpea mosaic virus (CPMV), for example, due to its size, monodispersity, and variety of chemical groups available for modification, makes a good scaffold for molecular assembly into nanoscale devices. The tobacco mosaic virus (TMV) was also used as bio-template, which has the shape of a linear tube, for assembly of various kinds of nanoparticles inside and outside the tubes. One can assemble gold nanoparticles onto the surfaces of polypeptide nanotubes while controlling their assembly position on the biomolecules using the specific affinities of the polypeptide sequences (16).
Cell mass or extracellular components from fungi, such as
Among the eukaryotic microorganism, yeast has been exploited mainly for the synthesis of semiconductors.
Algae are eukaryotic aquatic oxygenic photoautotrophs, which produce its food through photosynthesis using sunlight producing oxygen as their by-products. Their photosynthesis machinery has been evolved from cyanobacteria via endosymbiosis. They are predominant primary producers in many aquatic environments. Among various algae,
In that case, optimizing the conditions like pH, temperature and metal ions (solute) concentration for expediting the biological synthesis of nanoparticles with narrow size and shape is mandatory. To date, only very few reports have been documented on the optimization in biological processes. A 28-kDa “gold shape-directing protein (GSP)” present in the extract of green algae, C.
Indeed, a number of bacteria, fungi and yeast have been well-known for the synthesis of non-toxic noble nanoparticles. However the microbial mediated synthesis of nanoparticles is not industrially feasible as it requires expensive medium and maintenance of highly aseptic conditions. Hence, exploration of the plant systems as the potential bio-factories has gained heightened interest in the biological synthesis of nanoparticles. Hence, exploration into plant systems has been considered to be a potential bioreactor for synthesis of metal nanoparticles without using toxic chemicals.
Recently, we have reported that the various plant materials such as
Human cells are heterotrophic in nutrition. They need to be provided with energy for their survival. Human cancer cells and non-cancerous cells intracellularly produced some metal nanoparticles in vitro conditions that mimic their natural cellular environment. With an incubation of 1 mM of tetrachloroaurate solution, human cancer cells like SiHa (malignant cervical epithelial cells), SKNSH (human neuroblastoma) and HeLa (malignant cervical epithelial cells), and non-cancer cells like HEK-293 (non-malignant human embryonic kidney cells) synthesized gold nanoparticles in the size range of 20~100 nm. These nanoparticles were located in the cytoplasm and in the nucleus of the cells. The dimensions of these particles were smaller in nucleus compared to the cytoplasmic particles (33,34).
In producing nanoparticles using the intracellular and an extracellular extract of organisms, the extract is simply mixed with a solution of the metal salt at room temperature. The reaction is complete within minutes. Nanoparticles of silver, gold and other metals have been produced previously (35). Fig. 1 shows a picture of various organisms used for the biosynthesis of nanoparticles. The nature of the living extract, its concentration, the concentration of the metal salt, the pH, temperature and contact time are known to affect the rate of production of the nanoparticles, their quantity and other characteristics.
Mahendra
In the present study, we investigated whether these nanoparticles could induce nucleic acid DNA damage. For the assay of DNA damage, agarose gel electrophoresis was performed as per the manufacturer’s instructions using a commercially available DNA extraction kit (Bangalore Genei™, Bengaluru, India). The disc agar diffusion method was carried out to find the minimum inhibitory concentration of the AgNPs. Fig. 2 illustrates that 3 μg/mL shows the zone of inhibition around 7 mm including the disc (6 mm). 6 μg/mL which shows a little bigger zone of inhibition around 9 mm including the disc and this was taken for further analysis with field emission scanning electron microscopy (FE-SEM). Fig. 3 shows the FE-SEM images of the treated
The bacterial cells of Gram negative,
In agreement with the DNA damage, the amount of protein present in the cell suspension of the
In recent years, there is an increased interest in studying the novel metal nanoparticles. In particular, biological nanoparticles have been reported to produce various sources possessing as an antibacterial activity. Increasing awareness towards green chemistry and biological processes has led to a desire to develop an environment-friendly approach for the synthesis of non-toxic nanoparticles. Unlike other processes such as physical and chemical methods, which involve hazardous chemicals. Biosynthesis of nanoparticles is cost-effective and eco-friendly approach. Therefore, biosynthesis of nanoparticles has been emerged as an important branch of nanobiotechnology. Due to their rich diversity, microorganisms have the innate potential for the synthesis of nanoparticles and they could be regarded as potential biofactories for nanoparticles synthesis. However, to improve the rate of synthesis and monodispersity of nanoparticles, factors such as microbial cultivation methods and downstream processing techniques have to be improved. Further, the combinatorial approach such as photobiological methods may be used. For instance, a great deal of effort has been put into the biosynthesis of nanoparticles, especially metal nanoparticles using plants. The use of plants and plant products as sustainable and renewable resources in the synthesis of nanoparticles is more advantageous over prokaryotic microbes, which need expensive methodologies for maintaining microbial cultures and downstream processing. Furthermore, the biosynthesized nanoparticle was explained the role of silver nanoparticles in antibacterial application against Gram negative bacterial strain
Biological synthesis of metal nanoparticles using various organisms
Sources | Type of nanoparticles | Location | Size (nm) | References |
---|---|---|---|---|
Au | Extracellular | 15~30 | 9 | |
Ag | Intracellular | 200 | 11 | |
Ag & Au | Intra & Extracellular | 5~10 | 12 | |
U | Extracellular | 150 | 17 | |
Ag & Au | Intracellular | 60 | 46 | |
CdS | Intracellular | 2~5 | 24 | |
CdS | Intra & Extracellular | 2~5 | 47,48 | |
Au | Extracellular | 10~20 | 49 | |
Au | Intracellular | 25~33 | 50 | |
Au | Extracellular | 8 | 51 | |
Ag | Intracellular | 10~14 | 52 | |
Ag | Extracellular | 5~32 | 53 | |
Tobacco mosaic virus (TMV) | SiO2, CdS, PbS, Fe2O3 | Intra & Extracellular | 45~80 | 22 |
M13 bacteriophage | ZnS and CdS | Intra & Extracellular | 50~100 | 23 |
Ag | Extracellular | 71~74 | 54 | |
Ag | Extracellular | 5~15 | 55 | |
Ag | Intracellular | 25 | 56 | |
Ag | Extracellular | 5~25 | 57 | |
Ag | Extracellular | 13~18 | 58 | |
Ag | Extracellular | 50~200 | 56 | |
Magnetite | Extracellular | 20~50 | 59 | |
Au | Intracellular | 100 | 21 | |
CdS | Intracellular | 2~5 | 24 | |
CdS | Intracellular | 200 | 60 | |
CdS | Intracellular | 1~1.5 | 60 | |
Ag | Extracellular | 15~20 | 61 | |
Au | Extracellular | 9~20 | 62 | |
Ag | Intracellular | 2~20 | 26 | |
Ag and Au | Extracellular | 55~80 | 45 | |
Ag/Au | Extracellular | 50~100 | 63,64 | |
Ag | Extracellular | 16~40 | 65 | |
Au | Extracellular | 5~85 | 66 | |
Au | Extracellular | 50~350 | 67 | |
SiHa | Au | Intracellular | 20~100 | 33 |
HeLa | Au | Intracellular | 20~100 | 33,34 |
SKNSH | Au | Intracellular | 20~100 | 33 |
HEK-293 | Au | Intracellular | 20~100 | 33,34 |