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INTERNATIONAL RESEARCH JOURNAL OF PHARMACY www.irjponline.com ISSN 2230 – 8407

Research Article

SYNTHESIS OF SILVER NANOPARTICLES BY CHEMICAL REDUCTION METHOD

AND THEIR ANTIFUNGAL ACTIVITY Shenava Aashritha*

BDS, MDS (PhD), Department of Prosthodontics, AB Shetty Institute of Dental Sciences, Mangalore, India *Corresponding Author Email: keepthefaith999@yahoo.com

Article Received on: 30/09/13 Revised on: 07/10/13 Approved for publication: 11/10/13

DOI: 10.7897/2230-8407.041024 IRJP is an official publication of Moksha Publishing House. Website: www.mokshaph.com © All rights reserved. ABSTRACT The aim of this study was to evaluate the antimicrobial activity of silvercolloidal nanoparticles which were synthesised by chemical reduction. Silver nanoparticles were synthesized by reduction of silver nitrate with sodium citrate. The presence of silver nanoparticles was detected by atomic absorption spectroscopy. Antifungal activity of silver nanoparticles was detected by the zone of inhibition. Silver nanoparticles exhibited a characteristic surface plasmon resonance band that is measured by UV-Vis spectroscopy, showing a typical absorbance peak for nanoparticles centred at 430 nm. The antifungal activity of silver nanoparticles was measured by the zones of inhibition by Kirby Bauer sensitivity testing which were measured after 24 h of incubation at 370C of Candida albicans growth on sabouraud dextrose agar. This study, integrates nanotechnology leading to possible advances in the formulation of new types of fungicide. Keywords: Silver nanoparticles, surface Plasmon, UV-Vis absorption Spectrum, chemicals reduction. INTRODUCTION Silver ions are used in the formulation of dental resin composites; in coatings of medical devices; as a bactericidal coating in water filters; as an antimicrobial agent in air sanitizer sprays, pillows, respirators, socks, wet wipes, detergents, soaps, shampoos, toothpastes, washing machines, and many other consumer products; as bone cement; and in many wound dressings to name a few. Silver is generally used in the nitrate form to induce antimicrobial effect, but when silver nanoparticles are used, there is a huge increase in the surface area available for the microbe to be exposed to. There are many ways depicted in various literatures to synthesize silver nanoparticles. These include physical, chemical, and biological methods. The physical and chemical methods are numerous in number, and many of these methods are expensive1. The production of nanoparticles in physical and chemical processes can be obtained by both the so-called ‘top-down’ and ‘bottom-up’ methods. The top -down method involves the mechanical grinding of bulk metals and subsequent stabilization of the resulting nano sized metal particles by the addition of colloidal protecting agents2,3. The bottom-up methods, on the other hand, include reduction of metals, electrochemical methods, and sonodecomposition. The obtained nanoparticles with the size range of 3 to 40 nm are characterized by UV-visible (UV–vis) absorption spectroscopy to evaluate their quality4. There is the electrochemical method which involves the electro reduction of AgNO3 (silver nitrate) in aqueous solution in the presence of polyethylene glycol. The nanoparticles thus produced are characterized by TEM, X-ray diffraction, and UV–vis absorption spectroscopy and are 10 nm in diameter5. Sonodecomposition, to yield silver nanoparticles, involves the usage of ultrasonic waves to induce cavitations’, a phenomenon whereby the passage of ultrasonic waves through an aqueous solution yields microscopic bubbles that expand and ultimately burst. The synthesis of silver nanoparticles involves sonochemical reduction of an aqueous silver nitrate solution in an atmosphere of argon-hydrogen. The silver nanoparticles are then characterized by TEM, X-ray diffraction, absorption spectroscopy, differential scanning

calorimetry, and spectroscopy and are found to be 20 nm in diameter. The mechanism of the sonochemical reduction occurs due to the generation of hydrogen radicals during thesonication process6. There are also many more techniques of synthesizing silver nanoparticles, such as thermal decomposition in organic solvents7, chemical and photo reduction in reverse micelles8,9, spark discharge10, and cryochemical synthesis11. The problem with most of the chemical and physical methods of nano silver production is that they are extremely expensive and also involve the use of toxic, hazardous chemicals, which may pose potential environmental and biological risks. It is an unavoidable fact that the silver nanoparticles synthesized have to be handled by humans and must be available at cheaper rates for their effective utilization; thus, there is a need for an environmentally and economically feasible way to synthesize these nanoparticles. This study is a quest for such a method has led to the need for biomimetic production of silver nanoparticles whereby biological methods are used to synthesize the silver nanoparticles. The growing need to develop environmentally friendly and economically feasible technologies for material synthesis led to the search for bio mimetic methods of synthesis12. Chemical reduction is the most frequently applied method for the preparation of AgNPs as stable, colloidal dispersions in water or organic solvents. Commonly used reductants are borohydride, citrate, ascorbate and elemental hydrogen. The reduction of silver ions (Ag+) in aqueous solution generally yields colloidal silver with particle diameters of several nano meters. A multitude of chemical reduction methods have been applied to synthesize stable and various shapes of silver nanoparticles in water by the use of different reducing agents (ascorbic acid13, hydrazine14, dry methane15, dimethyl formamide16 and sodium borohydride17). The shape, size and the size distribution strongly depended on the strong and weak tendency of organic substrates to reduce the silver salts.

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MATERIAL AND METHOD Synthesis of colloidal nanoparticles Silver nanoparticles were synthesized by means of the turkevich method through the reduction of silver nitrate (AgNO3), Citrate of sodium (sigma aldrich). All chemicals were used as received. Double-distilled deionised water was used. The aqueous solution of silver nitrate (from 1, 0 mM to 6, 0 mM) and 8 % (w/w) and sodium citrate (1, 0 mM to 2, 0 mM) was kept at boiling temperature for a few of minutes until the solution turned amber yellow, indicating the formation of colloidal silver nanoparticles, confirmed by UV/Visible spectroscopy (Spectrophotometer Shimadzu MultSpec-1501, Shimadzu Corporation, Tokyo, Japan). The dispersions of silver nanoparticles display intense colours due to the plasmon resonance absorption. The surface of a metal is like plasma, having free electrons in the conduction band and positively charged nuclei. Surface Plasmon resonance is a collective excitation of the electrons inthe conduction band; near the surface of the nanoparticles. Electrons are limited to

specific vibrations modes by theparticle’s size and shape. Therefore, metallic nanoparticles have characteristic optical absorption spectrums in the UV-Vis region18. Antimicrobial test The antimicrobial efficacy of the silver nanoparticle colloidal suspension and of Ag nano composites against Candida albicans was evaluated by zone of growth inhibition and number of C. albicans colonies in agar plates, respectively. For contact biocidal property of silver nanoparticles, C. albicans diluted in 0.9 % NaCl (1 ± 0.2 × 10 CFU/mL) was plated onto Sabouraud dextrose agar (Sabouraud Dextrose Agar, Becton Dickinson France SAS, Le Pont de Claix, France). Sterile paper disks were placed on the agar and wetted with 10 μL of silver colloidal nanoparticles. These agar plates were incubated for 48 hours at 37°C ± 2°C. The zones of inhibition were visualized using Kirby-Bauer sensitivity test.

Figure 1: Chemical synthesis of silver nanoparticles

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Figure 2: UV–Vis absorption spectrum of silver nanoparticles prepared

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Figure 3: (a) Sabouraud Agar Plate; (b) Control Group; (c) Zone of Inhibition against Candida

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RESULTS Silver nanoparticles were synthesized according to the Turkevich method described in the previous section, the colloidal solution turned pale yellow indicating that the silver nanoparticles were formed. (Figure 1) shows the photograph of the chemical reduction procedure where uniform temperature was obtained. Silver nanoparticles are known to exhibit a characteristic surface plasmon resonance band that can be measured by UV-Vis spectroscopy (Figure 2) shows the plasmon band of the silver nanoparticle suspensions, showing a typical absorbance peak for nanoparticles centred at 430 nm. The symmetrical shape of the plasmon band can indicate a relative sharp particle size distribution. UV-visible spectroscopy is one of the most widely used techniques for structural characterization of silver nanoparticles. The particles range in size 14 nm with mean diameter 10 nm. Zones of inhibition were measured after 24 h of incubation at 370C. The comparativestability of discs (a) Sabouraud dextrose agar (b) Control group (c) Candidal suspension with discs dipped in AgNPs (1 ± 0.2 × 10 CFU/mL) shows the presence of certain level inhibited bacterial growth by more than 90 %, the zone of inhibition was 1 cm. The diameter of inhibition zones (in millimeters) around the different silver nanoparticles sols with against test strain are shown in (Figure 3). Antimicrobial activities of the synthesized silver colloidal sols were assessed using the standard dilution micro method, determining the minimum inhibitory concentration (MIC) leading to inhibition of bacterial growth (National Committee for Clinical Laboratory Standards. Performance standards for antimicrobial susceptibility testing; twelfth informational supplement. NCCLS document M100-S12. NCCLS, Wayne, Pennsylvania, 2002).Various regulatory agencies and standards-writing organizations subsequently published standardized reference procedures based on the Kirby-Bauer method. Among the earliest and most widely accepted of these standardized procedures were those published by the U.S. Food and Drug Administration (FDA) and the World Health Organization (WHO). DISCUSSION The size of metallic nanoparticles ensures that a significantly large surface area of the particles is in contact with the bacterial cells. Such a large contact surface is expected to enhance the extent of candidal elimination. The synthesis and characterisation of nano scaled materials in terms of novel physico-chemical properties is of great interest in the formulation of fungicidal materials. The extent of inhibition depends on the concentration of the silver nanoparticles as well as on the initial candidal population. This was supported by Sondi and Salopek (2004) who, reported that the interaction of these particles with intracellular substances from lysed cells caused their coagulation and the particles were thrown out of the liquid system. The mechanism of inhibitory action of silver ions on microorganism shows that upon Ag+ treatment, DNA loses its replication ability and expression of ribosomal subunit proteins, as well as other cellular proteins and enzymes essential to ATP production, becomes inactivated (Yamanaka et al., 2005). It has also been hypothesized that Ag+ primarily affects the function of membrane bound enzymes, in the respiratory chain. CONCLUSION Silver has always been an excellent antimicrobial and has been used for this purpose for ages. The unique physical and chemical properties of silver nanoparticles only increase the

efficacy of silver. Finally, this study shows that silver nanoparticles have excellent antibacterial activity against Candida albicans. This work, integrates nanotechnology and microbiology, leading to possible advances in the formulation of new types of fungicides. However, future studies on the biocidal influence of this nanomaterial on Candida albicans are necessary in order to fully evaluate its possible use as a new fungicidal material. REFERENCES 1. Sondi I, Salopek Sondi B. Silver nanoparticles as antimicrobial agent: A

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Cite this article as: Shenava Aashritha. Synthesis of silver nanoparticles by chemical reduction method and their antifungal activity. Int. Res. J. Pharm. 2013; 4(10):111-113 http://dx.doi.org/10.7897/2230-8407.041024