Desktop version

Home arrow Environment

  • Increase font
  • Decrease font


<<   CONTENTS   >>

Challenges of nanobioremediation

Although nanotechnology provides opportunities to develop novel techniques for use in detection as well as remediation of environmental pollution, there is debate about the impact of the nanoparticles on the environment and biological organisms (Wiesner et al. 2006, Colvin 2003). The extensive use of manufactured nanoparticles for industrial, commercial, medical and agricultural purposes is leading to their release into the environment, eventually leading to the contamination of the environment (Nowack 2009, Paschoalino et al. 2010). Recently, there is a lot of discussion on nanotoxicology, which relates to the toxicity of nanomaterials (Nowack 2008). Nanoparticles can enter the environment during the production of raw material and products, during its use and also after disposal of the products (Bundschuh et al. 2018). After their release in the environment, the nanoparticles undergo changes like chemical transformation, aggregation, and disaggregation. Some scientists have suggested that nanoparticles form reactive oxygen species in the environment that could affect biological structures and cause harmful effects to biological organisms (Moore 2006, Hund-Rinke and Simon 2006). Certain toxicity mechanism of nanoparticles reported are oxidative stress (Mwaanga et al. 2014, Wu and Zhou 2012), reproductive failure due to the modifications in hormones or hatching enzymes (Muller et al. 2015, Nair et al. 2011) and alteration in photosynthetic pigments of algae and aquatic plants (Zou et al. 2016, Jiang et al. 2017). Besides this, there are reports that nanoparticles cause biochemical and physiological changes in terrestrial plants (Du et al. 2017). Certain metal or metal oxide nanoparticles were found to be highly toxic for soil microorganisms and also have impact on soil microbial species diversity (Femandez-Luqueno et al. 2017, He et al. 2016). Silver nanoparticles were fovtnd to inhibit the activity of dehydrogenase (Murata et al. 2005), phosphornonoesterase, arylsulfatase,b-D-glucosidase and leucinearninopeptidase (Peyrot et al. 2014) in soil, while iron nanoparticles could stimulate enzyme activities in soil (He et al. 2011). Kiunar et al. (2012) reported that silver nanoparticles are toxic to the soil microbial community, especially to plant associated Bradyrhizobium canariense. Nanosized particles are reported to be taken up by different mammalian cells and are able to cross the cell membrane (Nel et al. 2006, Smart et al. 2006). Uptake of these particles is dependent on their size.

5.1.1 Health risk

Hiunan beings can be exposed to nanoparticle toxicity either by direct exposure through air, soil or water or indirectly through intake of plants or animals which have accumulated nanoparticles. Because of small particle size and large surface area, nanoparticles are able to disperse easily and form bonds in the environment and human tissues. Besides this, NPs are biopersistent and can enter the food chain. Certain nanomaterials (NM) react with proteins and enzymes leading to oxidative stress and generation of reactive oxygen species (ROS), which can destroy mitochondria and thereby cause apoptosis. The six main entry routes of NM to the biological systems are inhalation, dermal, oral, subcutaneous, intraperitoneal and intra venous. Inhalation of NMs cause deposition of NPs in respiratory' tract and lungs, which leads to lung related diseases like asthma, bronchitis, lung cancer, pneumonia, etc. NMs may penetrate into sweat glands and hair follicles. Skin exposure to cosmetics, sunscreens and dusts results in accumulation of nanoparticles, which are afterwards translocated to various parts of the body. These NMs remain in body in structurally unaltered, modified or metalized forms. They pass to the organs and remain in the cells for an indefinite peiiod of time. They may move to other organs or get excreted. NMs can cause toxic effects like allergy, fibrosis, organ failure, cytotoxicity, swelling and inflation, tissue scar and damage, reactive oxygen species generation and DNA damage.

Eco-friendly nanomaterials

Synthesis of eco-friendly nanomaterials to reduce the environmental hazards is needed in future. Hence, the concept of green nanotechnology is coming up, which is a combination of nanotechnology and green chemistry with the goal of creating eco-friendly nanomaterials to reduce the environmental and human health hazards (Paudey 2018). Green synthesis of nanomaterials refers to that remediation process which will not pose any environmental risk. The method should be such that minimal waste is produced, products used can be recycled, materials used are renewable, nanomaterials produced should not get converted to some other more harmful secondary' products after use and moreover it should be safe to use. In sum total, green synthesis of nanomaterial refers to avoiding production of undesirable, unsafe by-products and development of safe, sustainable and eco-friendly processes. In green synthesis, materials used are mostly microorganisms like algae, bacterial, fungi and plant materials. Researchers are using extracts from living organisms for synthesis of metallic nanoparticles. Most easy and readily available material for production of nanonraterial is plant extracts. Green nanoparticles could be produced by using reducing agents obtained front phytochenrical extracts of different plants’ parts (Boisselier and Astruc 2009, Shah et al. 2015). Different molecules like carbonyd groups, terpenoids, phenolic, flavones, amines, amides, proteins, pigments, and alkaloids, existing in both plant and microbial cells, may help in the synthesis of nanoparticles (Klaus et al. 1999). Microorganisms are also used for the synthesis of nanomaterials. Extracellular enzymes secreted by microbes are used for synthesis of green nanoparticles (Duran et al. 2011, Kupryashina et al. 2016). The metal binding ability of bacteria makes them useful for nanobioremediation. But fungi secrete more amount of protein, thereby producing larger amount of nanoparticles (Moghaddam et al. 2015). The methods of synthesizing nanoparticles involving microbes are slower than the methods involving plants. Some of the examples of biogenic nanomaterials are listed in Table 2.

Pollmann et al. (2006) reported that cells of bacteria Bacillus sphaericus JG-A12 (S-layer) were used for nano-remediation purposes as it was found that specifically these cells had high affinity for uranium and other heavy metals. A product called ‘bioceramics’ was prepared, where bacteiial cells were encapsulated into silica gels. These bioceramics were effectively capable of eliminating copper and uranium from contaminated sites. Thus, green synthesis of nanoparticles has huge potential in the field of nanoscience with least enviromnental risk and will gain attention in future among researchers to focus on green part of nano science with more efficient result being derived from plant based products and their extracts.

Table 2. List of biogenic nanomatenals.

Nanoparticles

Plant, bacteria, yeast and fungi

Silver - Germanium nanoparticles

Freshwater diatom Stauroneis sp.

Gold and silver nanoparticles

Saccharomyces cerevisiae, Citnts sinensis, Hibiscus rosasinensis, Mushroom extract, Verticillium sp., Fusarium oxysporum

Silver nanoparticles

Escherichia coli, Lactobacillus casei, Bacillus cereus, Aeromonas sp., Fusarium solani, Azadiracta indica, Brassica juncea, Aloe vera extract

Gold nanoparticles

Banana peel, Camellia sinensis, Chenopodium album, Rhodoseudomonas capsulate

Copper, zinc, nickel nanoparticles

Brassica juncea, Helianthus annuus, Medicago sativa

Platinum nanoparticles

Diopyros kaki, Ocimum sanctum

Palladium nanoparticles

Glycin max

Lead nanoparticles

Vitus vinifera, Jatropha carcus

 
<<   CONTENTS   >>

Related topics