Abstract
Plant constituents could act as chelating/reducing or capping agents for synthesis of silver nanoparticles (AgNPs). The green synthesis of AgNPs has been considered as an environmental friendly and cost-effective alternative to other fabrication methods. The present work described the biosynthesis of AgNPs using callus extracts from Taxus yunnanensis and evaluated their antibacterial activities in vitro and potential cytotoxicity in cancer cells. Callus extracts were able to reduce silver nitrate at 1 mM in 10 min. Transmission electron microscope (TEM) indicated the synthesized AgNPs were spherical with the size range from 6.4 to 27.2 nm. X-ray diffraction (XRD) confirmed the AgNPs were in the form of nanocrystals. Fourier transform infrared spectroscopy (FTIR) suggested phytochemicals in callus extracts were possible reducing and capping agents. The AgNPs exhibited effective inhibitory activity against all tested human pathogen bacteria and the inhibition against Gram-positive bacteria was stronger than that of Gram-negative bacteria. Furthermore, they exhibited stronger cytotoxic activity against human hepatoma SMMC-7721 cells and induced noticeable apoptosis in SMMC-7721 cells, but showed lower cytotoxic against normal human liver cells (HL-7702). Our results suggested that biosynthesized AgNPs could be an alternative measure in the field of antibacterial and anticancer therapeutics.
Highlights
As an important antibacterial agent, silver has been used for many years [1]
Many kinds of plant callus induced from papaya, alfalfa, Catharanthus roseus and Sesuvium portulacastrum have been applied in the green synthesis of agents for synthesis of silver nanoparticles (AgNPs) [7,8,9,10]
Our study showed that the biosynthesized AgNPs had significant antibacterial activity against the clinical bacteria strains (S. aureus, B. subtilis, E. coli and S. paratyphi B)
Summary
Silver nanoparticles (AgNPs) promoted the usage of silver in biomedical applications with its unique physic-chemical, optical and biological properties [2,3]. Several methods have been developed for the synthesis of AgNPs, including physical, chemical and biological methods [4,5]. The biological synthetic methods are preferred because they are safe, cheap and environment-friendly, whereas other physical and chemical methods require energy, high pressure, temperature and chemicals toxic to biological systems. Plants and microbes are currently used for AgNP synthesis among the biological synthetic methods [6]. A novel use of plant callus to synthesize AgNPs has been widely investigated. Applying plant callus in synthesizing AgNPs avoids various drawbacks including low yield, high expense, energy consumption in the physical approaches, and contamination in the wet-chemical procedure [11]. Callus extracts were more efficient in the fabrication of AgNPs and the synthesized AgNPs were more
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