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BIO00227 - BIOSYNTHESIS OF SILVER NANOPARTICLES FROM PLEUROTUS PULMONARIUS AQUEOUS EXTRACT AND


CHAPTER ONE

1.1       INTRODUCTION

Nanotechnology/Nanoscience

            Nanoscience and nanotechnology refers to the control and manipulation of matter at nanometer dimensions (Pradeep, 2008). Nature has evolved numerous incredibly functional assemblages of proteins, nucleic acids and other macromolecules to perform complicated tasks that are still daunting for us to emulate in our laboratories. One such task, which has been of great interest to material scientists, is the creation of the most efficient miniaturized functional materials by nature through ingenious ways. The interest towards nanoscience and nanotechnology is due to the relentless attempts to create functional miniaturized structures following nature’s way (Coleman et al., 2006).

Manufactured products are made from atoms, the properties of these products depend on how these atoms are arranged. This gap of 1-100nm size particles having 10-103 atoms or molecules per particle is a nanoparticle. In this nanoscale, neither quantum chemistry nor classical laws of physics hold (Smalley, 1999). In materials where strong chemical bonding is present, delocalization of valence electrons can be extensive. The extent of delocalization can vary with the size of the system. This effect, coupled with structural changes with size variation can lead to different physical and chemical properties, depending on size. Magnetic properties, optical properties, melting points, surface reactivity are some of the properties which are size dependent (Klabunde, 2002). The most important aspect of these Nano-size particles are synthesis, physical properties and chemical properties.

1.2       Nanomaterials

            Nanostructured materials have been attracting considerable attention because of their unique physical and chemical properties, which give them potential for important applications in many fields. The novel mechanical, optical, electronic and magnetic properties exhibited by Nanomaterials (NMs) over their corresponding bulk materials stimulates the interest in NMs. Inert substances such as gold for instance, will exhibit reactive properties when it is downsized to the nanoscale (Daniel and Astruc, 2004). Carbon nanotubes (CNTs), having the same chemical composition with brittle carbon compounds, show unique mechanical properties including a high tensile elastic modulus, flexibility and low density (Coleman et al., 2006). These distinctive properties may arise in part from the significant increase in the high surface-to-volume ratio as the particle size falls to the nanoscale and the domination of quantum effects on the properties of NMs (Owens and Poole Jr, 2008).

The ability to control the nanostructure of the materials can result in enhanced properties in macroscopic levels like increased hardness, ductility, selective absorption showing more efficient optical and electronic behavior. The critical issues for nanostructure synthesis fall into two categories:

  1. Control of the size and composition of the nanocluster components.
  2. Control of the interfaces and distributions of the nanoparticles within the fully formed materials.

1.3       Nanoparticles

                        Particles which have two or more dimensions in the size range as 1 to 100 nm are defined as nanoparticles (Alanazi et al., 2010).Scaling down material dimensions into the nanoscale may alter both physical and chemical properties of materials. The yellow colour of bulk gold material turns into deep-red colour when the gold size approach the nanoscale as has been recorded in the well-known work of Faraday in 1857 (Kelly et al., 2003; Daniel and Astruc, 2004). A number of methods of synthesizing Nanoparticles (NPs) has been developed and can be grouped into top-down (physical methods), bottom-up (chemical methods) and biological methods. Currently, there is an ever-growing need to develop environmentally benign nanoparticle synthesis processes. As a result, researchers in the field of nanoparticle synthesis and assembly have turned to biological systems for inspiration. This is not surprising given that many organisms, both unicellular and multicellular, are known to produce inorganic materials either intracellularly or extracellularly (Simkiss et al., 1989; Mann, 1986). Some well-known examples of bio-organisms synthesizing inorganic materials include magnetotactic bacteria (which synthesizemagnetite nanoparticles) (Loveley, 1987; Dickson, 1999), diatoms (which synthesize siliceous materials) (Mann, 1993; Pum et al., 1998) and S-layer bacteria (which produce gypsum and calcium carbonate layers) (Sleytr et al., 1999; Pum et al., 1999). The secrets gleaned from nature have led to the development of biomimetic approaches for the growth of advanced nanomaterials.

The promising novel properties and well-developed synthesis technology of NPs have accelerated the production and utilization of NPs in many consumer products. Silver nanoparticles (AgNPs) are particularly widely used as they exhibit wide-range antimicrobial properties. According to Woodrow Wilson Centre study, 313 out of 1317 nano-products contain AgNPs, and this figure has increased by more than ten times within five years (PEN, 2013). This rapid increase of AgNP commercialization raises concern over its potential release to the environment and the consequent adverse effects (Nowack and Bucheli, 2007; Ju-Nam and Lead, 2008). Therefore, the risk from NPs, as a function of exposure and the hazards, needs to be assessed either by an exposure-driven or a hazard-driven approach to prevent deleterious effect both on human and environmental health (Baalousha and Lead, 2007; Pettitt and Lead, 2013)

1.4       Mycosynthesis synthesis of AgNPs

                                Mushrooms are macrofungi which can be found in the wild and be cultivated on farms. The oyster mushroom Pleurotus spp. is a medicinal mushroom which has anticancer, antioxidant, antitumor, antiviral, antibacterial, antidiabetic, antihypercholesterolic, anti-arthritic, anti-yeast and antifungal activities. Recently, many studies began exploring the possibilities of nanoparticle (NP) synthesis employing various genera of edible and medicinal mushrooms owing to the innumerable bioactive compounds with diverse biological activities present within them. A vast variety of proteins and polysaccharides found in mushrooms has been utilized in the synthesis of both intracellular and extracellular gold (Au) and silver (Ag) NPs. The compounds secreted by medicinal mushrooms provide the NPs that are formed with high stability, extended shelf-life, water solubility and good dispersion properties. So far nano-experiments with mushrooms seem to be very promising and have opened up a new area of green-chemical approaches to form non-toxic, eco-friendly and stable nanomaterials, thus our knowledge of edible and medicinal mushrooms producing NPs is increasing day by day (Owaid, 2017).

The mycosynthetic method was developed to biosynthesize Ag-NPs that had distinct advantages over chemical methods such as their biosafety, non-toxicity and being highly environmental friendly. This is today called green chemistry or green nanotechnology. Myco-synthesizing means the synthesis of metal nanoparticles by using fungi/mushroom extract instead of another bio or chemical material. Thus, this type of chemistry known as green chemistry is a clean chemistry. This kind of synthesis which is cheap to implement and which uses natural energy led to the production of functionalized Ag-NPs on an industrial scale. This is very handy for using mushroom Ag-NPs for a wide range of applications in the nano field, because of the huge number of mycelia or fruiting bodies that are produced (Bhat et al., 2011).

The oyster mushroom Pleurotus spp. makes up more than 38% of mushrooms used in the nano field to mycosynthesize NPs, mostly Ag-NPs.  Pleurotus  ostreatus is used most among the species of this genus. The genus Agaricus sp. is the second most used (11%), especially A. bisporus. Schizophyllum commune is the third most used (10%), mostly in industrial applications using its polysaccharide (schizophyllan). Also, some mushroom genera are used such as Ganoderma sp. (9%), and some species such as Coriolus versicolor (4%), Vorvariella volvacea (3%), while others account for 25% including: Trametes sp., Lentinus sp., Tricholoma sp., Fomes fomentarieus, Inonotus obliquns, Pycnoporus sanguineus, Phellinus igniarius, Hypsizygus ulmarius, Polyporus rhinocerus, Microporus xanthopus, Helvela lacunose, Grifola frondosa, Hericium erinaceus, Pycnoporus sanguineus and Flammulina velutipes which have been applied to mycosynthesize NPs successfully. The role of mushrooms as effective nano-factories is attracting attention from many researchers in different fields worldwide. The mycogenic route for NPs synthesis has been well recognized because the eukaryota have several documented and remarkable features. Fungi can be used as an excellent resource of different extracellular enzymes that influence NPs synthesis (Saxena et al., 2014).

1.5       Aim and Objectives

Aim

            The aim of this research work is to employ a green synthesis approach of synthesizing silver nanoparticles using Pleurotus pulmonarius.

Objectives

  1. To synthesize silver nanoparticles using Pleurotus pulmonarius.
  2. Characterization of the synthesized Nanoparticles.
  3. To determine the antimicrobial activities of the synthesized Nanoparticles.
  4. To determine the thrombolytic assay of the synthesized Nanoparticle.