Optimization of biogenic synthesis of silver nanoparticles from flavonoid-rich Clinacanthus nutans leaf and stem aqueous extracts.
ABSTRACT: Background: Silver nanoparticles (AgNPs) are widely used in food industries, biomedical, dentistry, catalysis, diagnostic biological probes and sensors. The use of plant extract for AgNPs synthesis eliminates the process of maintaining cell culture and the process could be scaled up under a non-aseptic environment. The purpose of this study is to determine the classes of phytochemicals, to biosynthesize and characterize the AgNPs using Clinacanthus nutans leaf and stem extracts. In this study, AgNPs were synthesized from the aqueous extracts of C. nutans leaves and stems through a non-toxic, cost-effective and eco-friendly method. Results: The formation of AgNPs was confirmed by UV-Vis spectroscopy, and the size of AgNP-L (leaf) and AgNP-S (stem) were 114.7 and 129.9 nm, respectively. Transmission electron microscopy (TEM) analysis showed spherical nanoparticles with AgNP-L and AgNP-S ranging from 10 to 300 nm and 10 to 180 nm, with average of 101.18 and 75.38 nm, respectively. The zeta potentials of AgNP-L and AgNP-S were recorded at -42.8 and -43.9 mV. X-ray diffraction analysis matched the face-centred cubic structure of silver and was capped with bioactive compounds. Fourier transform infrared spectrophotometer analysis revealed the presence of few functional groups of phenolic and flavonoid compounds. These functional groups act as reducing agents in AgNPs synthesis. Conclusion: These results showed that the biogenically synthesized nanoparticles reduced silver ions to silver nanoparticles in aqueous condition and the AgNPs formed were stable and less toxic.
Project description:The increasing commercial production of engineered nanoparticles (ENPs) has led to concerns over the potential adverse impacts of these ENPs on biota in natural environments. Silver nanoparticles (AgNPs) are one of the most widely used ENPs and are expected to enter natural ecosystems. Here we examined the effects of AgNPs on germination and growth of eleven species of common wetland plants. We examined plant responses to AgNP exposure in simple pure culture experiments (direct exposure) and for seeds planted in homogenized field soils in a greenhouse experiment (soil exposure). We compared the effects of two AgNPs-20-nm polyvinylpyrrolidine-coated silver nanoparticles (PVP-AgNPs) and 6-nm gum arabic coated silver nanoparticles (GA-AgNPs)-to the effects of AgNO(3) exposure added at equivalent Ag concentrations (1, 10 or 40 mg Ag L(-1)). In the direct exposure experiments, PVP-AgNP had no effect on germination while 40 mg Ag L(-1) GA-AgNP exposure significantly reduced the germination rate of three species and enhanced the germination rate of one species. In contrast, 40 mg Ag L(-1) AgNO(3) enhanced the germination rate of five species. In general root growth was much more affected by Ag exposure than was leaf growth. The magnitude of inhibition was always greater for GA-AgNPs than for AgNO(3) and PVP-AgNPs. In the soil exposure experiment, germination effects were less pronounced. The plant growth response differed by taxa with Lolium multiflorum growing more rapidly under both AgNO(3) and GA-AgNP exposures and all other taxa having significantly reduced growth under GA-AgNP exposure. AgNO(3) did not reduce the growth of any species while PVP-AgNPs significantly inhibited the growth of only one species. Our findings suggest important new avenues of research for understanding the fate and transport of NPs in natural media, the interactions between NPs and plants, and indirect and direct effects of NPs in mixed plant communities.
Project description:Hybrid nanoparticles involving 10-nm silver nanoparticles (AgNPs) nucleated on unmodified rod-like cellulose nanocrystals (CNCs) were prepared by chemical reduction. H2O2 used as a post-treatment induced a size-shape transition following a redox mechanism, passing from 10-nm spherical AgNPs to 300-nm triangular or prismatic NPs (AgNPrisms), where CNCs are the only stabilizers for AgNPs and AgNPrisms. We investigated the role of the H2O2/AgNP mass ratio (?) on AgNPs. At ? values above 0.20, the large amount of H2O2 led to extensive oxidation that produced numerous nucleation points for AgNPrisms on CNCs. On the contrary, for ? below 0.20, primary AgNPs are only partially oxidized, releasing a reduced amount of Ag+ ions and thus preventing the formation of AgNPrisms and reforming spherical AgNPs. While XRD and EXAFS reveal that the AgNP fcc crystal structure is unaffected by the H2O2 treatment, the XANES spectra proved that the AgNP-AgNPrism transition is always associated with an increase in the metallic Ag fraction (Ag0). In contrast, the formation of new 15-nm spherical AgNPs keeps the initial Ag0/Ag+ ratio unmodified. For the first time, we introduce a complete guide map for the fully-controlled preparation of aqueous dispersed AgNPs using CNC as a template.
Project description:The growing use of silver nanoparticles (AgNPs) in consumer products raises concerns about potential health effects. This study investigated the persistence and clearance of 2 different size AgNPs (20 and 110?nm) delivered to rats by single nose-only aerosol exposures (6?h) of 7.2 and 5.4?mg/m(3), respectively. Rat lung tissue was assessed for silver accumulations using inductively-coupled plasma mass spectrometry (ICP-MS), autometallography, and enhanced dark field microscopy. Involvement of tissue macrophages was assessed by scoring of silver staining in bronchoalveolar lavage fluid (BALF). Silver was abundant in most macrophages at 1 day post-exposure. The group exposed to 20?nm AgNP had the greatest number of silver positive BALF macrophages at 56 days post-exposure. While there was a significant decrease in the amount of silver in lung tissue at 56 days post-exposure compared with 1 day following exposure, at least 33% of the initial delivered dose was still present for both AgNPs. Regardless of particle size, silver was predominantly localized within the terminal bronchial/alveolar duct junction region of the lung associated with extracellular matrix and within epithelial cells. Inhalation of both 20 and 110?nm AgNPs resulted in a persistence of silver in the lung at 56 days post-exposure and local deposition as well as accumulation of silver at the terminal bronchiole alveolar duct junction. Further the smaller particles, 20?nm AgNP, produced a greater silver burden in BALF macrophages as well as greater persistence of silver positive macrophages at later timepoints (21 and 56 days).
Project description:In the present study, microwave-assisted, optimized, instant, Terminalia bellirica fruit extract-mediated green synthesis of colloidal silver nanoparticles (AgNPs) has been reported. The synthesized AgNPs were characterized by UV-Vis spectroscopy, FTIR, Zetasizer, FESEM, EDX and XRD. The characteristic surface plasmon peak of reaction mixture at 406 nm confirmed the synthesis of AgNPs. The FTIR studies confirmed phytoconstituents were responsible for the synthesis and stability of AgNPs. The FESEM, EDX and XRD analysis revealed the presence of spherical silver nanoparticles of mean diameter ?20.6 nm with face-centered cubic crystalline structure. These AgNPs showed notable catalytic activity in reduction of 4-nitrophenol to 4-aminophenol in the presence of NaBH4. The synthesized AgNPs showed potential antibacterial and antibiofilm activity against bacterial pathogens like Bacillus subtilis, Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus. Thus, these synthesized AgNPs can open avenues for the development of AgNP-based efficient nanocatalyst and potent nanomedicine in future.
Project description:Silver nanoparticles (AgNPs) have been known for their inhibitory and bactericidal effects. In the present study, less toxic AgNPs using Cunninghamella echinulata is reported for the first time. The obtained AgNPs were characterized using UV-Visible spectrophotometer, XRD, FT-IR, FE-SEM with EDAX and HR-TEM. AgNPs showed the maximum absorbance at 420-430 nm. The transmission electron micrograph revealed the formation of considerably uniform-sized AgNPs with an average size of 20-50 nm. The reducing and capping agents responsible for AgNP synthesis were identified by FT-IR. AgNP-incorporated cotton fabrics exhibited promising antibacterial activity against pathogenic bacteria. In addition, the in vitro cell viability of Vero cells (African green monkey kidney cells) was analyzed and the IC50 value of AgNPs was found to be 62.8 µg/mL. Taken together, these results clearly reveal less toxic AgNPs which could be exploited for various biomedical applications.
Project description:The fresh water microalga Chlamydomonas reinhardtii bioreduced Ag? to silver nanoparticles (AgNPs) via three biosynthetic routes in a process that could be a more sustainable alternative to conventionally produced AgNPs. The AgNPs were synthesized in either the presence of whole cell cultures, an exopolysaccharide (EPS)-containing cell culture supernatant, or living cells that had been separated from the EPS-containing supernatant and then washed before being suspended again in fresh media. While AgNPs were produced by all three methods, the washed cultures had no supernatant-derived EPS and produced only unstable AgNPs, thus the supernatant-EPS was shown to be necessary to cap and stabilize the biogenic AgNPs. TEM images showed stable AgNPs were mostly spherical and showed a bimodal size distribution about the size ranges of 3.0 ± 1.3 nm and 19.2 ± 5.0 nm for whole cultures and 3.5 ± 0.6 nm and 17.4 ± 2.6 nm for EPS only. Moreover, selected area electron diffraction pattern of these AgNPs confirmed their polycrystalline nature. FTIR of the as-produced AgNPs identified polysaccharides, polyphenols and proteins were responsible for the observed differences in the AgNP stability, size and shape. Additionally, Raman spectroscopy indicated carboxylate and amine groups were bound to the AgNP surface.
Project description:We develop a novel nanohybrid showing a strong antibacterial activity on all of the tested pathogens, including methicillin-resistant Staphylococcus auerus and silver-resistant E. coli. The nanohybrid consists of silver nanoparticles (AgNPs) supported on 1 nm-thick silicate platelets (NSPs). The AgNP/NSP nanohybrid enables to encapsulate bacteria and triggers death signals from the cell membrane. The geographic shape of the NSPs concentrates AgNPs but impedes their penetration into attached cells, mitigating the detrimental effect of silver ion deposition in applied tissues. Moreover, the tightly tethered AgNPs on NSP surface achieve a stronger biocidal effect than silver nitrate, but bypassing Ag(+) mechanism, on silver-resistant bacteria. This nanohybrid presents an effective and safe antimicrobial agent in a new perspective.
Project description:BACKGROUND:Development of multidrug resistance (MDR) is a major burden of successful chemotherapy, therefore, novel approaches to defeat MDR are imperative. Although the remarkable anti-cancer propensity of silver nanoparticles (AgNP) has been demonstrated and their potential application in MDR cancer has been proposed, the nanoparticle size-dependent cellular events directing P-glycoprotein (Pgp) expression and activity in MDR cancer have never been addressed. Hence, in the present study we examined AgNP size-dependent cellular features in multidrug resistant breast cancer cells. RESULTS:In this study we report that 75 nm AgNPs inhibited significantly Pgp efflux activity in drug-resistant breast cancer cells and potentiated the apoptotic effect of doxorubicin, which features were not observed upon 5 nm AgNP treatment. Although both sized AgNPs induced significant ROS production and mitochondrial damage, 5 nm AgNPs were more potent than 75 nm AgNPs in this respect, therefore, these effects can not to be accounted for the reduced transport activity of ATP-driven pumps observed after 75 nm AgNP treatments. Instead we found that 75 nm AgNPs depleted endoplasmic reticulum (ER) calcium stores, caused notable ER stress and decreased plasma membrane positioning of Pgp. CONCLUSION:Our study suggests that AgNPs are potent inhibitors of Pgp function and are promising agents for sensitizing multidrug resistant breast cancers to anticancer drugs. This potency is determined by their size, since 75 nm AgNPs are more efficient than smaller counterparts. This is a highly relevant finding as it renders AgNPs attractive candidates in rational design of therapeutically useful agents for tumor targeting. In the present study we provide evidence that exploitation of ER stress can be a propitious target in defeating multidrug resistance in cancers.
Project description:Among all classes of nanomaterials, silver nanoparticles (AgNPs) have potentially an important ecotoxicological impact, especially in freshwater environments. Fish are particularly susceptible to the toxic effects of silver ions and, with knowledge gaps regarding the contribution of dissolution and unique particle effects to AgNP toxicity, they represent a group of vulnerable organisms. Using cell lines (RTL-W1, RTH-149, RTG-2) and primary hepatocytes of rainbow trout (Oncorhynchus mykiss) as in vitro test systems, we assessed the cytotoxicity of the representative AgNP, NM-300K, and AgNO3 as an Ag+ ion source. Lack of AgNP interference with the cytotoxicity assays (AlamarBlue, CFDA-AM, NRU assay) and their simultaneous application point to the compatibility and usefulness of such a battery of assays. The RTH-149 and RTL-W1 liver cell lines exhibited similar sensitivity as primary hepatocytes towards AgNP toxicity. Leibovitz's L-15 culture medium composition (high amino acid content) had an important influence on the behaviour and toxicity of AgNPs towards the RTL-W1 cell line. The obtained results demonstrate that, with careful consideration, such an in vitro approach can provide valuable toxicological data to be used in an integrated testing strategy for NM-300K risk assessment.
Project description:Silver exposure is toxic to fish due to disturbances of normal gill function. A proposed toxicity mechanism of silver nanoparticles (AgNP) is derived from the release of silver ions, similar to silver nitrate (AgNO3). However, some datasets support the fact that AgNP can have unique toxic effects that are mediated at the gill. To determine if differences between AgNO3 and AgNP toxicities exist, fathead minnows were exposed to 20 nm PVP- or citrate-coated silver nanoparticles (PVP-AgNP; citrate-AgNP) at the nominal concentration of 200 μg/L or AgNO3 at nominal 6 μg/L for 96 hr. This nominal concentration was applied to approximate the dissolved fraction of Ag in the AgNP suspensions. Mucus production in the water was measured. While mucus production was initially significantly increased in the first 4 h of exposure in all silver treatments compared to control, a decrease in mucus production was observed following 24-96 h of exposure. To determine which genes/pathways are driving this shift in mucus production, gills were dissected and microarray analysis was performed. Hierarchal clustering of differentially expressed genes revealed that all samples distinctly clustered by treatment. There were 109 differentially expressed genes shared among all Ag treatments compared to controls. However, there were 185, 423, and 615 differentially expressed genes unique to AgNO3, PVP-AgNP, and citrate-AgNP, relative to control. While functional analysis indicated several common enriched pathways, such as aryl hydrocarbon receptor signaling, this analysis also indicated some unique pathways between nanosilver and AgNO3. Our results show that AgNO3, PVP-AgNP, and citrate-AgNP exposure affected mucus production in fish gills and also lead to common and unique transcriptional changes. Overall design: To explore the effects of silver and silver nanoparticles on fathead minnow gills, we explored cellular transcriptional responses following exposure of fathead minnow (Pimephales promelas) to either AgNO3, citrate or PVP-coated silver nanoparticles. After 96h of exposure, total RNA was isolated from samples RNeasy (Qiagen, Valencia, CA, USA) for microarray analysis. Three to five replicates were used per treatment.