INTRODUCTION:

Nanotechnology is an emerging field in the area of interdisciplinary research, especially in biotechnology.¹ Nanoparticle research is inevitable today not because of only application and also by the way of synthesis.² Silver nanoparticles have been widely used in different fields.³ Silver nanoparticles are important materials that have been studied extensively; such nanoparticles possess unique electrical, optical as well as biological properties and are thus applied in catalysis, biosensing, imaging, drug delivery, nanodevice fabrication and in medicine.⁴

Synthesis of silver nanoparticles was extensively studied employing chemical and physical methods, but the development of reliable technology to produce nanoparticles is an important aspect of nanotechnology.⁵

Synthesis of nanoparticles by physical and chemical methods may have considerable environmental defect, technically laborious and economically expensive.⁶ The biological methods, using microorganisms and enzymes, have been suggested as possible eco-friendly alternatives. The plants or plants extract, which act as reducing and capping agents for nanoparticles synthesis, are more advantageous over other biological processes, because they eliminate the elaborated process of culturing and maintaining of the cell, and can also be scaled up for large-scale nanoparticle synthesis.⁷ Moreover, plant-mediated nanoparticles synthesis is preferred because it is cost-effective, environmentally friendly, a single-step method for biosynthesis process and safe for human therapeutic use. Different parts of plant materials such as extracts, fruit, bark, fruit peels, root and callus have been studied so far for the synthesis of silver, gold, platinum and titanium nanoparticles in different sizes and shapes.⁸

In recent years, green synthesis of silver nanoparticles (AgNPs) has gained much interest from chemists and researchers.^9,10 In this concern, Indian flora has yet to divulge innumerable sources of cost-effective non-hazardous reducing and stabilizing compounds utilized in preparing AgNPs.¹¹ Therefore, this study is an attempt to optimize the synthesis process of silver nanoparticles preparation from leaf extracts of Musa balbisiana (banana) by varying the different physical parameter during the biosynthesis process.

MATERIALS AND METHODS:

Preparation of the leaf extract:

M. balbisiana (banana) was selected from Ahmedabad, Gujarat, India, on the basis of cost-effectiveness, ease of availability and medicinal property. Fresh and healthy leaves were collected locally and rinsed thoroughly first with tap water followed by distilled water to remove all the dust and unwanted visible particles, cut into small pieces and dried at room temperature. About 10 g of these finely incised leaves were weighed separately and transferred into 250 mL beakers containing 100 mL distilled water and boiled for about 20 min. The extract was then filtered thrice through Whatman No. 1 filter paper to remove particulate matter and to get clear solution which was then refrigerated (4°C) in 250 mL Erlenmeyer flask for further experiments. In each and every step of the experiment, sterility conditions were maintained for the effectiveness and accuracy in results without contamination.

Effect of Different Parameter on the Synthesis of Silver Nanoparticles:

In order to standardize the synthesis of silver nanoparticles the different physical parameters like the concentration of AgNO₃ (1-8) mM, the pH of leaf extract (5-12), temperature 5-50° C of the reaction mixture, incubation time (0-120 h) and salinity (0.1-1.0%) of the leaf extract have been investigated.

RESULTS:

Concentration of AgNO₃ plays an important role in the synthesis and size of nanoparticles. The intensity of absorbance at 420nm increases with the increase of concentration up to 4 mM conc. and then decreases and 40mM was found to be maximum. This may be due to secretion of nitrate reductase by the banana leaf increases till a threshold concentration reach. The same can be observed in the figure 1 below.

Reduction of metal ion is dependent on PH of the solution. It was found that synthesis initially decreases with the increase of PH up to PH 6 and then increases up to PH 9 and finally decreases. This is due to in absence of alkaline solution the time taken for reduction of silver ions is longer indicating the need of OH- ions for the reduction reaction. The enzyme nitrate reductase catalyzing the synthesis was probably deactivated when nitrate reductase was at acidic and more alkaline condition. The same can be observed in the figure 2 below.

Figure 1: Relation of concentration of nanoparticles to concentration of AgNO₃

Figure 2: Relation of the metal ion to PH of the solution

Temperature has an important role in showing enzyme activity and it was observed that at 300°C the synthesis and stability of nanoparticles was found to be maximum. At this temperature both the rate of adsorption of AgNO₃ and viscosity of the coat phase may be enhanced. The same can be observed in the figure 3 below.

Figure 3: Relation of temperature to the rate of adsorption of AgNO₃ and viscosity of the coat phase

The rate of synthesis of silver nanoparticles was dependent on incubation time of the reaction mixture. With time the intensity of color and absorbance at 420 nm was found to be enhanced gradually till 72 h incubation and then both remained nearly constant. The same can be observed in the figure 4 below.

Figure 4: Relation of the rate of synthesis of silver nanoparticles with incubation time of the reaction mixture

Salinity has very little effect on the synthesis process of the silver nanoparticles as obtained from the result. But it was observed that at 0.2% NaCl concentration the absorption max at 420nm is high in the study set as well as a little change on color of leaf extract have been observed. Concentrations of NaCl above 0.2% were unfavorable for the nanoparticles synthesis. Deactivation of enzyme by excess salt may have reflected in lower absorbance values. The same can be observed in the figure 5 below.

Figure 5: Deactivation of enzyme by excess salt may have reflected in lower absorbance values

DISCUSSION:

The silver nanoparticles can be synthesized by green technology using the leaves of banana. Low stability and big size are the practical limitation for application. So, by varying the physical parameter to standardize the biosynthesis process it was observed that at 4mM AgNO₃ conc., a pH of around 9, temperature of 300°C, and an incubation time of 72 h with 0.2% salinity the synthesis as well as stability of silver nanoparticles was maximum which can be considered as optimum condition. The present study reports an eco-friendly, cost efficient, rapid and easy method for synthesis of silver nanoparticles using banana leaves extract as a reducing and capping agent.

ACKNOWLEDGMENTS:

We acknowledge for all the helping hands who helped to conduct this study.

CONFLICTS OF INTEREST:

The authors declare that they have no conflict of interest.

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Received on 30.12.2020 Modified on 14.02.2021

Research J. Pharm.and Tech 2022; 15(2):870-872.

DOI: 10.52711/0974-360X.2022.00145