Characterization, antioxidant and antimicrobial activities of green synthesized silver nanoparticles from Psidium guajava L. leaf aqueous extracts.

The green synthesis of nanoparticles has become increasingly promising due to their potential applications in nanomedicine and materials science. In this study, silver nanoparticles (P-AgNPs) were synthesized from aqueous extracts of P. guajava L. leaf. The synthesized silver nanoparticles were confirmed by UV-vis spectrophotometry at 438 nm. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and zetasizer analyses showed that the average sizes of the P-AgNPs were 20-35 nm, 25 nm, and 25-35 nm, respectively. Element mapping analyses of the P-AgNPs were confirmed by X-ray diffraction (XRD) and energy dispersive X-ray spectroscopy (EDX) analyses. Moreover, FTIR spectra of the synthesized P-AgNPs showed the presence of phyto constituents as capping agents. Zeta potential measurements (-20.17 mV) showed that the synthesized P-AgNPs had reasonably good stability. The in vitro antioxidant properties of the P-AgNPs were evaluated using two different methods. A highly efficient radical scavenging activity of P-AgNPs possessing IC50 values of 52.53 ± 0.31 μg/mL (DPPH) and 55.10 ± 0.29 μg/mL (ABTS+) were confirmed. At a concentration of 100 μg/mL, antimicrobial activity assays of the P-AgNPs showed significant inhibition against selected bacteria, S. cerevisiae, A. niger and R. oryzae, especially against Alcaligenes faecalis and Escherichia coli. The present study revealed that the low-cost and environmentally friendly synthesis of P-AgNPs can be widely used in biomedicine, water treatment or purification, and nanobiotechnology.

Wang L ，Wu Y ，Xie J ，Wu S ，Wu Z ... -  《-》

Comparison of biogenic silver nanoparticles formed by Momordica charantia and Psidium guajava leaf extract and antifungal evaluation.

Nguyen DH ，Vo TNN ，Nguyen NT ，Ching YC ，Hoang Thi TT ... -  《PLoS One》

Garlic, green tea and turmeric extracts-mediated green synthesis of silver nanoparticles: Phytochemical, antioxidant and in vitro cytotoxicity studies.

Phyto-synthesis of silver nanoparticles (AgNPs) was achieved using aqueous garlic, green tea and turmeric extracts, and characterized by different spectroscopic techniques. Phytochemical analysis revealed the presence of rich amount of biochemicals in these extracts, which serve as reducing and capping agents for converting silver nitrate into AgNPs. FT IR spectroscopy confirmed the role of biomolecules in the bioreduction and efficient stabilization of AgNPs. UV-Vis DRS spectra showed a band around 450 nm characteristics of AgNPs. XRD patterns revealed the crystalline nature of the synthesized AgNPs with fcc structure. SEM and TEM analysis revealed the spherical shape of the synthesized AgNPs with an average particle size of 8 nm. EDX analysis confirmed the purity of the synthesized AgNPs with a strong signal at 3.2 keV. The antioxidant activity was assessed by ABTS, DPPH, p-NDA, H2O2 and DMSO scavenging assays, in which the AgNPs synthesized using green method showed remarkable activity with respect to the standard antioxidants ascorbic acid and rutin. In vitro cytotoxicity activity was tested on four cancer cell lines such as human breast adenocarcinoma (MCF-7), cervical (HeLa), epithelioma (Hep-2) and lung (A549) along with one normal human dermal fibroblasts (NHDF) cell line. The AgNPs synthesized using turmeric extract exhibits excellent antioxidant and cytotoxicity activity compared to that synthesized using other extracts.

Arumai Selvan D ，Mahendiran D ，Senthil Kumar R ，Kalilur Rahiman A ... -  《-》

Preliminary investigation of catalytic, antioxidant, anticancer and bactericidal activity of green synthesized silver and gold nanoparticles using Actinidia deliciosa.

Herein we report a rapid low cost one step green synthetic method using Actinidia deliciosa fruit extract for preparation of stable and multifunctional silver and gold nanoparticles. The synthesized nanoparticles were successfully used as green catalysts for the reduction of 4-nitrophenol (4-NP) and methylene blue (MB). The enhanced biological activity of the prepared nanoparticles was investigated based on its highly stable antioxidant, anticancer and bactericidal effects. TEM micrographs showed that the silver nanoparticles (AgNPs) formed were predominantly spherical in shape having diameters ranging from 25 to 40nm, while gold nanoparticles (AuNPs) shown particle size ranges from 7 to 20nm. EDAX (energy-dispersive X-ray spectroscopy) and XPS (X-ray photoelectron spectroscopy) results confirmed the presence of elemental silver and gold. X-ray diffraction (XRD) pattern revealed the formation of face-centered cubic structure for AgNPs and AuNPs. The Fourier-transform infrared (FTIR) spectrum indicated the presence of possible functional groups in the biomolecule responsible for capping the nanoparticles. The AgNPs treated HCT116 cells showed 78% viability at highest concentration (350μg/mL), while AuNPs showed 71% viability at highest concentration (350μg/mL) using MTT assay, which provides promising approach for alternative nano-drug development. The antimicrobial activity of the nanoparticles was investigated using Pseudomonas aeruginosa (P.aeruginosa) in which damaging the cell membrane was observed by TEM images. Our results revealed that the green synthesis method is easy, rapid, inexpensive, eco-friendly and efficient in developing multifunctional nanoparticles in near future in the field of biomedicine, water treatment and nanobiotechnology.

Naraginti S ，Li Y 《-》

Photo-catalyzed and phyto-mediated rapid green synthesis of silver nanoparticles using herbal extract of Salvinia molesta and its antimicrobial efficacy.

Current study presents an economic, ecofriendly and simple photo-catalytic green route for the swift biosynthesis of silver nanoparticles (AgNPs) within 20s, devoid of any instrumental support or chemical reductant. Aqueous leaf-extract of an aquatic fern, Salvinia molesta (AES), was used as a bioreductant as well as a stabilizing agent. Rapid change in color of reaction mixture from yellowish green to reddish brown within 20s in direct sun light exposure was considered as the primary visual indication of AgNPs biosynthesis. The biosynthesis of AgNPs was confirmed by UV-visible spectroscopy through the presence of a characteristic surface plasmon resonance (SPR) band for AgNPs at λmax of 425 nm. The process parameters were optimized through one factor at a time approach. Optimal values of different process parameters for the current biosynthetic system were found as; 35 min of reaction time under sun light, 8.0mM AgNO3 concentration and 5.0% (v/v) AES inoculum dose. Field emission scanning electron microscopy (FESEM), energy dispersive X-Ray spectroscopy (EDX), high resolution transmission electron microscopy (HRTEM), atomic force microscopy (AFM) and X-ray diffraction (XRD) analysis showed that most of AgNPs were spherical in shape with average size distribution of 12.46 nm having face centered cubic (fcc) crystal lattice. IR analysis of AES and synthesized AgNPs indicated the involvement of both hydroxyl and amino groups in the biosynthesis and stabilization of AgNPs. The synthesized AgNPs were found to be an effective antibacterial agent against both Gram positive and Gram negative bacteria. On the basis of results and facts, a probable mechanism has also been proposed to explore the possible route of biosynthesis of AgNPs through AES.

Verma DK ，Hasan SH ，Banik RM 《-》