Elsevier

Materials Letters

Volume 264, 1 April 2020, 127353
Materials Letters

Rapid and size-controlled biosynthesis of cytocompatible selenium nanoparticles by Azadirachta indica leaves extract for antibacterial activity

https://doi.org/10.1016/j.matlet.2020.127353Get rights and content

Highlights

  • A size-controlled SeNPs biosynthesis is achieved by Azadirachta indica leaves extract.

  • Spherical and smooth SeNPs of size ~153 and ~278 nm are synthesized.

  • FT-IR studies reveal presence of polyphenols, flavonoids and proteins on the SeNPs surface.

  • As prepared SeNPs are cytocompatible to mammalian cells in-vitro.

  • SeNPs show concentration dependent broad spectrum antibacterial activity.

Abstract

Biosynthesized selenium nanoparticles (SeNPs) have achieved considerable importance in biomedical applications owing to their biocompatibility and low toxicity. In this study, rapid and size-controlled biosynthesis of SeNPs by aqueous leaves extract of Azadirachta indica is reported. SeNPs were synthesized by reduction of Se+ ions of sodium selenite salt to elemental selenium. Biosynthesized SeNPs were crystalline in nature and spherical in shape with a smooth surface. The size of these SeNPs was controlled by adjusting the time of reduction reaction. Accordingly, SeNPs of size range 142 to 168 nm and 221 to 328 nm were synthesized after 5 and 10 min of reaction respectively with 10 mM initial concentration of sodium selenite. Fourier Transform- Infra Red (FT-IR) analysis revealed the presence of plant extract molecules on the surface of SeNPs acting as reducing agent and capping molecules. These biosynthesized SeNPs were found to be cytocompatible in nature when tested in-vitro against the L929 cell line by MTT assay. In addition, these biosynthesized SeNPs showed promising antibacterial activity against selected Gram-positive and Gram-negative bacterial strains.

Introduction

Numerous reports in the last decade clearly demonstrated the advantages of biogenic selenium nanoparticles (SeNPs) over physically and chemically synthesized SeNPs due to biocompatibility, nontoxic nature, colloidal stability and avoidance of extreme temperature and pressure in synthesis method [1]. Among different biosynthesis routes available, plant mediated SeNPs biosynthesis have gained significant attraction due to the simplicity of reaction and ease of purification [2]. In recent studies, various plant sources and plant materials were successfully employed for the biosynthesis of SeNPs [3]. However, none of these studies was successful in rapid biosynthesis of SeNPs with the capability to control the size of the nanoparticles [Table S1]. Therefore, it was important to develop a rapid plant mediated SeNPs synthesis method offering considerable control on the size of synthesized nanoparticles. Published reports regarding antibacterial activity of chemically synthesized [4] and biosynthesized [5], [6] SeNPs demonstrated the potential of SeNPs as an antibacterial agent against Gram-positive and Gram-negative bacterial strains. Responding to these facts, present study deals with the rapid and size-controlled biosynthesis of SeNPs by aqueous leaves extract of Azadirachta indica as a green chemistry approach, and investigation of in-vitro cytocompatibility and antibacterial potential of these SeNPs.

Section snippets

Preparation of leaves extract

Details are provided in the Supplementary file.

Biosynthesis and purification of SeNPs

Details are provided in the Supplementary file.

Characterizations of SeNPs

Details are provided in the Supplementary file.

Antibacterial and cytocompatibility evaluation

Purified SeNPs were tested for antibacterial activity against two Gram-negative bacteria Proteus vulgaris (NCIM- 2027) and Pseudomonas aeruginosa (NCIM- 2036), and two Gram-positive bacteria Staphylococcus aureus (NCIM- 2079) and Bacillus cereus (NCIM-2217). All bacterial strains were procured from National Center for Industrial Microorganisms (NCIM),

Results and discussion

When sodium selenite salt was added into the 100 ml aqueous leaves extract of Azadirachta indica and incubation of this reaction mixture at 37 °C and 100 rpm, there was a color change in the reaction mixture from light green to pink and finally to reddish pink. This characteristic change in coloration from pink to reddish pink was attributed to a difference in the size of SeNPs as a reaction progresses and it was due to surface plasma resonance of SeNPs [9]. After 10 min of incubation, no

Conclusions

Size-controlled biosynthesis of SeNPs from the Azadirachta indica leaves extract is a simple, robust, eco-friendly, inexpensive and rapid method. Two different sized, ~153 and ~287 nm, spherical and smooth surfaced SeNPs were biosynthesized by varying the time of reduction reaction. Polyphenols, flavonoids and proteins in the leaves extract acted as capping molecules on the surface of these SeNPs. These biosynthesized SeNPs showed concentration dependent broad spectrum antibacterial activity

CRediT authorship contribution statement

Shivaji Pawar is a project administrator and supervises the work. Shivaji Pawar and Nayeem Mulla conceptualized the work and experiments. Nayeem Mulla and Sachin Otari developed the methodology and performed the experiments (Investigation). Raghvendra Bohara and Hemraj Yadav performed the software and formal analysis of the experimental data. Nayeem Mulla, Sachin Otari and Shivaji Pawar wrote and revised the manuscript. All authors analyzed the results and reviewed the manuscript.

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgment

Authors are grateful to University Grants Commission (UGC), New Delhi, India, for financial support under UGC-NET-JRF fellowship program (No. F.17-177/2014 (SA-I)).

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