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We synthesized silver nanoparticles using thirty Chinese plant extracts via a green synthetic strategy. UV–visible spectra showed that the silver nanoparticles have an absorbance at 450 nm. Among the thirty extracts, seven extracts (Cratoxylum formosum , Phoebe lanceolata , Scurrula parasitica , Ceratostigma minus , Mucuna birdwoodiana , Myrsine africana and Lindera strychnifolia) exhibited the successful synthesis of silver nanoparticles. These seven extracts showed higher 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity and reducing power than the other extracts. The silver nanoparticles synthesized using these seven extracts were mostly spherical with high colloidal stability. The cytotoxicity of these seven silver nanoparticle samples on human lung cancer cells (A549) was clearly higher than that of the extracts alone. Furthermore, the cytotoxicity was affected by the presence or absence of fetal bovine serum. Moreover, the cytotoxicity of the silver nanoparticles synthesized with Cratoxylum formosum and Mucuna birdwoodiana extracts resulted in apoptotic cell death in A549 cells. The wound healing activity observed by the cell scratch method on mouse fibroblast cells (NIH3T3) suggested that the Lindera strychnifolia extract produced silver nanoparticles with decent activity. These results provide ample and systematic information for researchers on the green synthesis of silver nanoparticles using plant extracts. Unlabelled Image • Thirty plant extracts are used for green synthesis of silver nanoparticles. • Synthetic process is totally green and eco-friendly. • Plant extracts play a role as a reducing and a stabilizing agent. • Silver nanoparticles exert biological activities. [ABSTRACT FROM AUTHOR]

Silver nanoparticle has been widely applied to a variety of fields for its outstanding antimicrobial activity. However, the stability of silver nanoparticle limits its application under certain conditions. Thus, improving the stability of silver nanoparticle via biosynthesis is a promising shortcut to expand its application. Sericin from silkworm cocoon has good hydrophilicity, reaction activity, biocompatibility and biodegradability. In this study, we developed a novel, simple, one-step biosynthesis method to prepare sericin-silver nanoparticle composite in situ in solution. Sericin served as the reductant of silver ion, the dispersant and stabilizer of the prepared sericin-silver nanoparticle composite. Natural light was the only power source used to catalyze the synthesis of silver nanoparticle in situ in solution. The novel sericin-silver nanoparticle composite was characterized by ultraviolet-visible and fluorescence spectroscopy, X-ray diffraction, transmission electron microscopy and fourier transform infrared spectroscopy. The results showed silver nanoparticle could be synthesized through the reduction of AgNO 3 by the phenolic hydroxyl group of tyrosine residues of sericin under the catalysis of natural light. The synthesized silver nanoparticle had good crystalline, size distribution and long-term stability at room temperature. Light irradiation was essential for the preparation of sericin-silver nanoparticle composite. The antibacterial activity assay showed 25 mg/L and 100 mg/L were the minimum concentrations of sericin-silver nanoparticle composite required to inhibit the growth of Staphylococcus aureus and kill this bacterium, respectively. The cytotoxicity assay showed cell viability and cell growth were almost not affected by sericin-silver nanoparticle composite under the concentration of 25 mg/L. Our study suggested the preparation of sericin-silver nanoparticle composite was environmentally friendly and energy conservation, and the prepared sericin-silver nanoparticle composite had long-term stability, effective antibacterial activity and good biocompatibility. This novel sericin-silver nanoparticle composite has shown great potentials for biomedical application such as antibacterial agent and wound care. [ABSTRACT FROM AUTHOR]

Silver nanoparticles (AgNPs) were synthesized via a green strategy using fifty-eight plant extracts that originated from Vietnam and Indonesia. Among the fifty-eight AgNP samples, we selected six AgNP samples synthesized by the extracts of Areca catechu , Hypotrachyna laevigata , Ardisia incarnata , Maesa calophylla , Maesa laxiflora and Adinandra poilanei. Remarkably, these six extracts exhibited higher 2,2-diphenyl-1-picrylhydrazyl radical scavenging activity and reducing power than the other extracts. Furthermore, the contents of total phenolic compounds and reducing sugars in the six selected extracts were also higher than those in the other extracts. The six selected AgNP samples showed strong surface plasmon resonance in the range of 416–438 nm. They were all spherical shaped with an average size from 12.5 ± 1.0 nm to 21.3 ± 4.9 nm as measured by field-emission transmission electron microscopy images. The hydrodynamic sizes were measured to be 49.5–122.6 nm with negative zeta potential values. Colloidal stability was excellent on the shelf for 28 days and in cell culture medium. The cytotoxicity assessment and generation of reactive oxygen species (ROS) in A549 and HeLa cells demonstrated that the AgNP samples prepared by Ardisia incarnata , Maesa calophylla , and Maesa laxiflora showed relatively high cytotoxicity and excess ROS generation among the six selected AgNP samples. Exposure of the AgNP samples to A549 and HeLa cells resulted in cell death, which was mostly due to necrosis but slightly due to late apoptosis. Cell cycle analysis demonstrated a significant increase in the cell population in the S phase. The green-synthesized AgNPs induced cell death, suggesting anticancer prospects that may offer new insight into the development of an anticancer nanomedicine. Unlabelled Image • Fifty-eight plant extracts are used for green synthesis of silver nanoparticles. • Synthetic process is totally sustainable and green. • Silver nanoparticles are cytotoxic and generate ROS in cancer cells. • Silver nanoparticles induce cell death via mostly necrosis. [ABSTRACT FROM AUTHOR]

Green synthesis of nanoparticles (NPs) involves the use of diverse extracts of biological origin as substrates to synthesize NPs and can overcome the hazards associated with chemical methods. Coconut inflorescence sap, which is unfermented phloem sap obtained by tapping of coconut inflorescence, is a rich source of sugars and secondary metabolites. In this study, coconut inflorescence sap was used to synthesize silver NPs (AgNPs). We have initially undertaken metabolomic profiling of coconut inflorescence sap from West Coast Tall cultivar to delineate its individual components. It was found to comprise of 64% secondary metabolites, 9% sugars, 12% lipids/fats and 9% peptides in positive mode, whereas in the negative mode, it was 33, 20, 9 and 11%, respectively. The concentration of silver nitrate, inflorescence sap and incubation temperature for the synthesis of AgNPs were optimized. Incubating the reaction mixture at 40 °C was found to enhance AgNP synthesis. The AgNPs synthesized were characterized using UV–visible (UV-Vis) spectrophotometry, X-Ray Diffraction (XRD), Fourier Transform Infrared spectroscopy (FTIR) and Transmission Electron Microscopy (TEM). The particles were crystalline in nature and the bulk of the particles were spherical with smooth (thin) shell and poly-dispersed with a diameter ranging from 10 nm to 30 nm. Antimicrobial property of AgNPs was tested in tissue culture of arecanut (Areca catechu L.) where bacterial contamination (Bacillus pumilus) was a frequent occurrence. A significant reduction in the contamination was observed when plantlets were treated with aqueous solutions of AgNPs. Notably, treatment with AgNPs did not affect the growth and development of the arecanut plantlets. Antimicrobial properties of AgNPs synthesized from inflorescence sap were also evaluated in human pathogenic bacteria viz., Escherichia coli ATCC 25922; Salmonella Typhimurium ATCC 14028 and Vibrio parahaemolyticus AQ4037. The antibacterial action was confirmed by determining the production of reactive oxygen species (ROS) and protein leakage studies. Cytotoxicity of AgNPs was quantified in HeLa cells. The viability (%) of HeLa cells declined significantly at 10 mg L−1 concentration of AgNP and complete mortality was observed at a concentration of 60 mg L−1. The study concludes that unfermented inflorescence sap, with above neutral pH, serves as an excellent reducing agent to synthesize AgNPs from Ag+. Unlabelled Image • Coconut inflorescence sap is a rich source of metabolites, sugars, lipids & peptides. • Coconut inflorescence sap was used to synthesize silver nanoparticles (AgNPs). • The AgNPs synthesized were characterized extensively. • Its antimicrobial and cytotoxic properties were also assessed. [ABSTRACT FROM AUTHOR]