Abstract
The present study reports that the biosynthesis of AgNPs using an endophytic fungus isolated from the ethnomedicinal plant Centella asiatica. The endophytic fungus was identified as Aspergillus versicolor ENT7 based on 18S rRNA gene sequencing (NCBI Accession number KF493864). The AgNPs synthesized were characterized by UV–visible spectroscopy, Fourier transform infra-red spectroscopy (FTIR), transmission electron microscopy (TEM), X-ray diffraction (XRD), particle size analyzer, and zeta potential measurements. The UV–Vis absorption spectra showed the peak at 429 nm which confirmed the synthesis of AgNPs. TEM analysis revealed that the AgNPs were spherical in shape with 3–40 nm in size; similar results were also obtained by Horiba particle size analyzer with 5–40 nm in size. The synthesized AgNPs were highly stable due to their high negative zeta potential value of −38.2 mV. XRD studies showed (111), (200), (220), (311), and (222) planes of the face-centered cubic (FCC) lattice, indicating the crystalline nature of the AgNPs. Selected area electron diffraction (SAED) pattern of the AgNPs showed five circular fringes which were in accordance with XRD data and confirmed the formation of high crystalline nature of AgNPs. FTIR measurements indicated the peaks at 3273, 2925, 1629, 1320, and 1020 cm−1 corresponding to different functional groups possibly involved in the synthesis and stabilization of AgNPs. The synthesized AgNPs exhibited effective free radical scavenging activity with the IC50 value of 60.64 µg/ml. The synthesized AgNPs were found to be highly toxic against both gram-positive and gram-negative bacteria and also showed a very good antifungal activity.
Highlights
Over the last decade majority of the researchers shifted their focus to nanometer-sized particles, metal nanoparticles because of their controllable size and shape, ease of synthesis, and strong optical properties
The present study reports that the biosynthesis of AgNPs using an endophytic fungus isolated from the ethnomedicinal plant Centella asiatica
We report the biosynthesis of AgNPs using extracellular filtrate of endophytic fungus Aspergillus versicolor ENT7 strain isolated from the healthy leaf tissues of Centella asiatica, an important medicinal plant which harbors many endophytic fungi
Summary
Over the last decade majority of the researchers shifted their focus to nanometer-sized particles, metal nanoparticles because of their controllable size and shape, ease of synthesis, and strong optical properties. Noble metal nanoparticles silver nanoparticles (AgNPs) have gained a significant interest in the recent years, owing to their remarkable optical, optoelectronic, magnetic, catalytic, and thermal properties and find applications as optical receptors (Karimzadeh and Mansour 2010), sensors (Cobley et al 2009), catalysts in chemical 132 Page 2 of 9. Irradiation and other physical methods are not environmental friendly and possess health risks. Hazardous chemicals, such as hydroxylamine, poly-N-vinyl pyrrolidine, polyvinyl alcohol, and sodium borohydride, are involved in the chemical approaches. The application of chemical approaches is not eco-friendly and possesses biological risks, and the toxic chemicals on the surface limit the applications of AgNPs in pharmaceutical and biomedical fields. Fungi being eukaryotes produce high amounts of proteins and other biomolecules. Various fungi have been reported to synthesize AgNPs, including Alternaria alternate (Monali et al 2009), Amylomyces rouxii (Javed et al 2010), Aspergillus niger (Netala et al 2015b), Coriolus versicolor (Rashmi and Varma 2009), Fusarium solani (Rafie et al 2012), Humicola sp (Asad et al 2013), Neurospora crossa (Longoria et al 2011), Schizophyllum radiatum (Metuku et al 2014), and Trichoderma viride (Fayaz et al 2009) have been reported
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