Oxide-silver Nanocomposite Research Articles

Graphene Oxide-Silver Nanocomposite Enhances Cytotoxic and Apoptotic Potential of Salinomycin in Human Ovarian Cancer Stem Cells (OvCSCs): A Novel Approach for Cancer Therapy.

The use of graphene to target and eliminate cancer stem cells (CSCs) is an alternative approach to conventional chemotherapy. We show the biomolecule-mediated synthesis of reduced graphene oxide–silver nanoparticle nanocomposites (rGO–Ag) using R-phycoerythrin (RPE); the resulting RPE–rGO–Ag was evaluated in human ovarian cancer cells and ovarian cancer stem cells (OvCSCs). The synthesized RPE–rGO–Ag nanocomposite (referred to as rGO–Ag) was characterized using various analytical techniques. rGO–Ag showed significant toxicity towards both ovarian cancer cells and OvCSCs. After 3 weeks of incubating OvCSCs with rGO–Ag, the number of A2780 and ALDH+CD133+ colonies was significantly reduced. rGO–Ag was toxic to OvCSCs and reduced cell viability by mediating the generation of reactive oxygen species, leakage of lactate dehydrogenase, reduced mitochondrial membrane potential, and enhanced expression of apoptotic genes, leading to mitochondrial dysfunction and possibly triggering apoptosis. rGO–Ag showed significant cytotoxic potential towards highly tumorigenic ALDH+CD133+ cells. The combination of rGO–Ag and salinomycin induced 5-fold higher levels of apoptosis than each treatment alone. A combination of rGO–Ag and salinomycin at very low concentrations may be suitable for selectively killing OvCSCs and sensitizing tumor cells. rGO–Ag may be a novel nano-therapeutic molecule for specific targeting of highly tumorigenic ALDH+CD133+ cells and eliminating CSCs. This study highlights the potential for targeted therapy of tumor-initiating cells.

An In Vitro Study of the Photodynamic Effectiveness of GO-Ag Nanocomposites against Human Breast Cancer Cells.

Graphene-based materials have garnered significant attention because of their versatile bioapplications and extraordinary properties. Graphene oxide (GO) is an extremely oxidized form of graphene accompanied by the functional groups of oxygen on its surface. GO is an outstanding platform on which to pacify silver nanoparticles (Ag NPs), which gives rise to the graphene oxide-silver nanoparticle (GO-Ag) nanocomposite. In this experimental study, the toxicity of graphene oxide-silver (GO-Ag) nanocomposites was assessed in an in vitro human breast cancer model to optimize the parameters of photodynamic therapy. GO-Ag was prepared using the hydrothermal method, and characterization was done by X-ray diffraction, field-emission scanning electron microscope (FE-SEM), transmission Electron Microscopy (TEM), energy dispersive X-rays Analysis (EDAX), atomic force microscopy and ultraviolet-visible spectroscopy. The experiments were done both with laser exposure, as well as in darkness, to examine the phototoxicity and cytotoxicity of the nanocomposites. The cytotoxicity of the GO-Ag was confirmed via a methyl-thiazole-tetrazolium (MTT) assay and intracellular reactive oxygen species production analysis. The phototoxic effect explored the dose-dependent decrease in the cell viability, as well as provoked cell death via apoptosis. An enormously significant escalation of 1O2 in the samples when exposed to daylight was perceived. Statistical analysis was performed on the experimental results to confirm the worth and clarity of the results, with p-values < 0.05 selected as significant. These outcomes suggest that GO-Ag nanocomposites could serve as potential candidates for targeted breast cancer therapy.

Combination of graphene oxide-silver nanoparticle nanocomposites and cisplatin enhances apoptosis and autophagy in human cervical cancer cells.

BackgroundCisplatin (Cis) is a widely used chemotherapeutic drug for treating a variety of cancers, due to its ability to induce cell death in cancer cells significantly. Recently, graphene and its modified nanocomposites have gained much interest in cancer therapy, due to their unique physicochemical properties. The objective of this study was to investigate the combination effect of Cis and a reduced graphene oxide–silver nanoparticle nanocomposite (rGO-AgNPs) in human cervical cancer (HeLa) cells.Materials and methodsWe synthesized AgNPs, rGO, and rGO-AgNP nanocomposites using C-phycocyanin. The synthesized nanomaterials were characterized using various analytical techniques. The anticancer properties of the Cis, rGO-AgNPs, and combination of Cis and rGO-AgNPs were evaluated using a series of cellular assays, such as cell viability, cell proliferation, LDH leakage, reactive oxygen species generation, and cellular levels of oxidative and antioxidative stress markers such as malondialdehyde, glutathione, SOD, and CAT. The expression of proapoptotic, antiapoptotic, and autophagy genes were measured using real-time reverse-transcription polymerase chain reaction.ResultsThe synthesized AgNPs were well dispersed, homogeneous, and spherical, with an average size of 10 nm and uniformly distributed on graphene sheets. Cis, GO, rGO, AgNPs, and rGO-AgNPs inhibited cell viability in a dose-dependent manner. The combination of Cis and rGO-AgNPs showed significant effects on cell proliferation, cytotoxicity, and apoptosis. The combination of Cis and rGO-AgNPs had more pronounced effects on the expression of apoptotic and autophagy genes, and also significantly induced the accumulation of autophagosomes and autophagolysosomes, which was associated with the generation of reactive oxygen species.ConclusionOur findings substantiated rGO-AgNPs strongly potentiating Cis-induced cytotoxicity, apoptosis, and autophagy in HeLa cells, and hence rGO-AgNPs could be potentially applied to cervical cancer treatment as a powerful synergistic agent with Cis or any other chemotherapeutic agents.

One-step Electrochemically Modulated Synthesis of Reduced Graphene Oxide-Silver Nanocomposites as Efficient Nonenzymatic H2O2 Sensor

One-step Electrochemically Modulated Synthesis of Reduced Graphene Oxide-Silver Nanocomposites as Efficient Nonenzymatic H2O2 Sensor

PEDOT-reduced graphene oxide-silver hybrid nanocomposite modified transducer for the detection of serotonin

We have developed PEDOT - reduced graphene oxide - silver hybrid nanocomposite (PEDOTNTs/rGO/Ag NPs) modified electrode as a transducer for the detection of serotonin. Structure and properties of the nanocomposites were characterized by XPS, XRD, SEM, TEM, FT-IR, UV–Visible, and Raman spectroscopy. The electrochemical impedance spectroscopic (EIS) results showed a very low charge transfer resistance (198Ω) for the modified electrode and its sensing performance towards serotonin studied by various electrochemical techniques such as cyclic voltammetry (CV), differential pulse voltammetry (DPV) and chronoamperometry (CA). PEDOTNTs/rGO/AgNPs/GCE showed better performance by DPV with a lower detection limit of 0.1nM with high operational stability, reproducibility (inter- and intra-electrode - 2.3%) response time (8s) and sensitivity (14.304μAmM−1/cm2). It also showed a liner range from 1nM to 0.5mM (linear regression equation y=6.33 e−6 x+0.153 e−6). The kinetics of serotonin oxidation was studied by chronoamperometry and the catalytic rate constant calculated as 1.647×103mol−1Ls−1. Later, the modified electrode demonstrated as a transducer for the selective detection of serotonin in the presence of ascorbic acid, uric acid and tyrosine. Real sample analysis and interference studies suggested the modified electrode can be exploited in pharmaceutical and medical fields.

TiO 2 nanofibers assembled on graphene-silver platform as a visible-light photo and bio-active nanostructure

Abstract The heterogeneous titanium oxide-reduced graphene oxide-silver (TiO2/RGO/Ag) nanocomposites were successfully prepared by incorporation of two dimensional (2D) RGO nanosheets and spherical silver nanoparticles (NPs) into the 1D TiO2 nanofibers. The novel TiO2/RGO/Ag nanocomposites were synthesized by loading TiO2 nanofibers, prepared via electrospinning technique, on the RGO/Ag platform. The resulting nanocomposites have been characterized using various techniques containing transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and ultra-violet-visible (UV–vis) spectroscopy. Microscopic studies clearly verified the existence of TiO2 nanofibers with Ag NPs on the surface of RGO sheet and formation of TiO2/RGO/Ag nanocomposites. Moreover, the results of UV–vis spectroscopy demonstrated that TiO2/RGO/Ag nanocomposites extended the light absorption spectrum toward the visible region and significantly enhanced the visible-light photocatalytic performance of the prepared samples on degradation of rhodamine B (Rh. B) as a model dye. It was found that, incorporation of 50 µl RGO/Ag into the TiO2 nanofibers lead to a maximum photocatalytic performance. Also, the improvement of the inactivation of Escherichia coli (E. coli) bacteria under visible-light irradiation was revealed by introduction of RGO/Ag into the TiO2 matrix. The significant enhancement in the photo and bio-activity of TiO2/RGO/Ag nanocomposites under visible-light irradiation can be ascribed to the RGO/Ag content by acting as electron traps in TiO2 band gap.

Functional Iron Oxide–Silver Hetero-Nanocomposites: Controlled Synthesis and Antibacterial Activity

Iron oxide-silver nanocomposites are of great interest for their antibacterial and antifungal activities. We report a two-step synthesis of functional magnetic hetero-nanocomposites of iron oxide nanoparticles and silver nanoparticles (Fe3O4-Ag). Iron oxide nanoparticles were prepared first by a co-precipitation method followed by the deposition of silver nanoparticles via a hydrothermal route. The prepared Fe3O4-Ag hetero-nanocomposites were characterized by x-ray diffraction, transmission electron microscopy, high resolution transmission electron microscopy and vibrating sample magnetometry. Their antibacterial activities were investigated by using paper-disc diffusion and direct-drop diffusion methods. The results indicate that the Fe3O4-Ag hetero-nanocomposites exhibit excellent antibacterial activities against two Gram-negative bacterial strains (Salmonella enteritidis and Klebsiella pneumoniae).

Photo-assisted advanced oxidation processes for Rhodamine B degradation using ZnO–Ag nanocomposite materials

Zinc oxide–silver nanocomposite materials (ZnO–Ag)NCM were successfully synthesized by facile solid-state pyrolysis method. The synthesized materials were characterized by various techniques like UV-DRS, PL, XRD, FE-SEM and TEM. The morphological analysis has clearly showed that the silver nanoparticles are incorporated on zinc oxide nanorods. The silver nanoparticle/ZnO nanorods found to be an efficient zinc oxide–silver nanocomposite, which effectively moderated the rate of charge recombination and also offered visible photo-absorption. Formerly, the silver metal acts as both electron sink and visible photosensitizer. The photocatalytic performance of the nanocomposite materials was investigated on the degradation of organic pollutant rhodamine B (RhB) under solar, UV and visible light irradiation. The photocatalytic performance of nanocomposite materials was also explored in presence of ultrasonic waves. Moreover, the common oxidants like persulfate and peroxide were also combined with the photocatalytic investigation. The results revealed that the ZnO–Ag nanocomposite materials were found to be an efficient photocatalytic activity towards the degradation of rhodamine B with photo-assisted advanced oxidation processes (PAOPs).

Antibiofilm efficacy of green synthesized graphene oxide-silver nanocomposite using Lagerstroemia speciosa floral extract: A comparative study on inhibition of gram-positive and gram-negative biofilms.

Biofilm architecture provides bacteria with enhanced antibiotic resistance, thus raising the need to search for alternative therapies that can inhibit the bacterial colonization. In the present study, we synthesized graphene oxide-silver nanocomposite (GO-Ag) by non-toxic and eco-friendly route using a floral extract of Legistromia speciosa (L.) Pers. The gas chromatography-mass spectrometry (GC-MS) analysis of plant extract revealed the presence of compounds which can simultaneously act as reducing and capping agents. The sub-inhibitory concentrations of synthesized GO-Ag reduced the biofilm formation in both gram-negative (E.cloacae) and gram-positive (S.mutans) bacterial models. Growth curve assay, membrane integrity assay, scanning electron microscopy (SEM) and confocal scanning laser microscopy (CSLM) revealed different mechanisms of biofilm inhibition in E.cloacae and S.mutans. Moreover, quantitative RT-PCR (qRT-PCR) results suggested GO-Ag is acting on S.mutans biofilm formation cascade. Biofilm inhibitory concentrations GO-Ag were also found to be non-toxic against HEK-293 (human embryonic kidney cell line). The whole study highlights the therapeutic potential of GO-Ag to restrain the onset of biofilm formation in bacteria.

Cellulose acetate membrane embedded with graphene oxide-silver nanocomposites and its ability to suppress microbial proliferation

Bacterial adhesion and consequent biofilm formation are one the biggest hurdles in membrane-based technologies. Due to numerous problems associated with bacterial colonization on membrane surfaces, the development of new approaches to prevent microbial growth has been encouraged. Graphene oxide, produced by the chemical exfoliation of graphite, is a highly water-dispersible nanomaterial which has been used as a platform for the anchoring of nanoparticles and bioactive molecules. In this present study, we propose the fabrication of antimicrobial membranes through the incorporation of graphene oxide-silver nanocomposites into a cellulose acetate polymeric matrix. Transmission electron microscopy, Raman, and UV–visible diffuse reflectance spectroscopy measurements confirmed the presence of graphene oxide-silver sheets in the modified membranes. In comparison to pristine membranes, membranes containing graphene oxide-silver nanocomposites showed larger surface pores and increased pure water flux. In addition, membranes embedded with graphene oxide-silver presented strong antibacterial activity, being able to inactivate adhered bacteria at a rate of 90% compared to pristine cellulose acetate membranes. Our results strongly suggest that the incorporation of graphene oxide-silver nanocomposites to cellulose acetate is a promising strategy to produce membranes that are able to minimize bacterial attachment and growth.

Thin-film composite forward osmosis membranes functionalized with graphene oxide–silver nanocomposites for biofouling control

Innovative approaches to prevent bacterial attachment and biofilm growth on membranes are critically needed to avoid decreasing membrane performance due to biofouling. In this study, we propose the fabrication of anti-biofouling thin-film composite membranes functionalized with graphene oxide–silver nanocomposites. In our membrane modification strategy, carboxyl groups on the graphene oxide–silver nanosheets are covalently bonded to carboxyl groups on the surface of thin-film composite membranes via a crosslinking reaction. Further characterization, such as scanning electron microscopy and Raman spectroscopy, revealed the immobilization of graphene oxide–silver nanocomposites on the membrane surface. Graphene oxide–silver modified membranes exhibited an 80% inactivation rate against attached Pseudomonas aeruginosa cells. In addition to a static antimicrobial assay, our study also provided insights on the anti-biofouling property of forward osmosis membranes during dynamic operation in a cross-flow test cell. Functionalization with graphene oxide–silver nanocomposites resulted in a promising anti-biofouling property without sacrificing the membrane intrinsic transport properties. Our results demonstrated that the use of graphene oxide–silver nanocomposites is a feasible and attractive approach for the development of anti-biofouling thin-film composite membranes.

Graphene Oxide-Silver Nanocomposite: Novel Agricultural Antifungal Agent against Fusarium graminearum for Crop Disease Prevention.

Nanoparticle-based antibacterial agents have emerged as an interdisciplinary field involving medicine, material science, biology, and chemistry because of their size-dependent qualities, high surface-to-volume ratio, and unique physiochemical properties. Some of them have shown great promise for their application in plant protection and nutrition. Here, GO-AgNPs nanocomposite was fabricated through interfacial electrostatic self-assembly and its antifungal activity against phytopathogen Fusarium graminearum was investigated in vitro and in vivo for the first time. The results demonstrated that the GO-AgNPs nanocomposite showed almost a 3- and 7-fold increase of inhibition efficiency over pure AgNPs and GO suspension, respectively. The spore germination inhibition was stimulated by a relatively low concentration of 4.68 μg/mL (minimum inhibition concentration (MIC)). The spores and hyphae were damaged, which might be caused by an antibacterial mechanism from the remarkable synergistic effect of GO-AgNPs, inducing physical injury and chemical reactive oxygen species generation. More importantly, the chemical reduction of GO mediated by fungal spores was possibly contributed to the high antimicrobial activity of GO-AgNPs. Furthermore, the GO-AgNPs nanocomposite showed a significant effect in controlling the leaf spot disease infected by F. graminearum in the detached leaf experiment. All the results from this research suggest that the GO-AgNPs nanocomposite developed in this work has the potential as a promising material for the development of novel antimicrobial agents against pathogenic fungi or bacteria.

Hydrothermal preparation of reduced graphene oxide-silver nanocomposite using Plectranthus amboinicus leaf extract and its electrochemical performance.

Graphene based nanocomposites are receiving increasing attention in many fields such as material chemistry, environmental science and pharmaceutical science. In this study, a facial synthesis of a reduced graphene oxide-silver nanocomposite (RGO-Ag) was carried out from Plectranthus amboinicus leaf extract. The synthesized nanocomposite was characterized by using X-ray diffraction, scanning electron microscope, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscope and UV-vis spectroscopy for structural confirmation. The reduction of graphene oxide and silver ions was achieved simultaneously due to the reducibility of the Plectranthus amboinicus leaf extract. We further investigated the electrochemical properties of the biosynthesized RGO-Ag nanocomposite. A nonenzymatic H2O2 electrochemical sensor was shown to be successfully fabricated by using biosynthesized RGO-Ag nanocomposite. Moreover, the fabricated electrochemical sensor also showed good selectivity.

Antibacterial properties and mechanism of graphene oxide-silver nanocomposites as bactericidal agents for water disinfection

Providing clean and affordable drinking water without harmful disinfection byproducts generated by conventional chemical disinfectants gives rise to the need for technological innovation. Nanotechnology has great potential in purifying water and wastewater treatment. A graphene oxide-silver (GO-Ag) nanocomposite with excellent antibacterial activity was prepared and characterized by transmission electron microscope and X-ray photoelectron spectroscopy. The tests were carried out using Escherichia coli and Staphylococcus aureus as model strains of Gram-negative and Gram-positive bacteria, respectively. The effect of bactericide dosage and pH on antibacterial activity of GO-Ag was examined. Morphological observation of bacterial cells by scanning electron microscope showed that GO-Ag was much more destructive to cell membrane of Escherichia coli than that of Staphylococcus aureus. Experiments were carried out using catalase, superoxide dismutase and sodium thioglycollate to investigate the formation of reactive oxygen species and free silver ions in the bactericidal process. The activity of intracellular antioxidant enzymes was measured to investigate the potential role of oxidative stress. According to the consequence, synergetic mechanism including destruction of cell membranes and oxidative stress accounted for the antibacterial activity of GO-Ag nanocomposites. All the results suggested that GO-Ag nanocomposites displayed a good potential for application in water disinfection.

Comparative in vitro toxicity of a graphene oxide-silver nanocomposite and the pristine counterparts toward macrophages.

BackgroundGraphene oxide (GO) is a highly oxidized graphene form with oxygen functional groups on its surface. GO is an excellent platform to support and stabilize silver nanoparticles (AgNP), which gives rise to the graphene oxide-silver nanoparticle (GOAg) nanocomposite. Understanding how this nanocomposite interacts with cells is a toxicological challenge of great importance for future biomedical applications, and macrophage cells can provide information concerning the biocompatibility of these nanomaterials. The cytotoxicity of the GOAg nanocomposite, pristine GO, and pristine AgNP was compared toward two representative murine macrophages: a tumoral lineage (J774) and peritoneal macrophages collected from Balb/c mouse. The production of reactive oxygen species (ROS) by J774 macrophages was also monitored. We investigated the internalization of nanomaterials by transmission electron microscopy (TEM). The quantification of internalized silver was carried out by inductively coupled plasma mass spectrometry (ICP-MS). Nanomaterial stability in the cell media was investigated overtime by visual observation, inductively coupled plasma optical emission spectrometry (ICP OES), and dynamic light scattering (DLS).ResultsThe GOAg nanocomposite was more toxic than pristine GO and pristine AgNP for both macrophages, and it significantly induced more ROS production compared to pristine AgNP. TEM analysis showed that GOAg was internalized by tumoral J774 macrophages. However, macrophages internalized approximately 60 % less GOAg than did pristine AgNP. The images also showed the degradation of nanocomposite inside cells.ConclusionsAlthough the GOAg nanocomposite was less internalized by the macrophage cells, it was more toxic than the pristine counterparts and induced remarkable oxidative stress. Our findings strongly reveal a synergistic toxicity effect of the GOAg nanocomposite. The toxicity and fate of nanocomposites in cells are some of the major concerns in the development of novel biocompatible materials and must be carefully evaluated.Electronic supplementary materialThe online version of this article (doi:10.1186/s12951-016-0165-1) contains supplementary material, which is available to authorized users.

Controlled synthesis of reduced graphene oxide supported silver nanoparticles for selective and sensitive electrochemical detection of 4-nitrophenol

An electrochemical sensing platform made of a reduced graphene oxide-silver (rGO-Ag) nanocomposite was developed for the detection of 4-nitrophenol. The synthesis of the nanocomposite was monitored at different reaction times (2h, 6h, 10h and 15h) in modified Tollens’ test and characterized using UV-visible absorption spectrum, transmission electron microscopy (TEM), X-ray diffraction (XRD), and Raman spectroscopy analyses. Completely spherical Ag nanoparticles (NPs) were found at a reaction time of 15h with an average particle size of 16nm. The nanocomposites prepared with different reaction times were used for the electrocatalytic reduction of 4-NP, and the rGO-Ag (15h) nanocomposite-modified glassy carbon (GC) electrode displayed a higher faradaic current at an overpotential of −0.5V toward 4-NP reduction. The rGO-Ag (15h) nanocomposite-modified electrode was used for the square wave voltammetric (SWV) detection of 4-NP in a 0.1M phosphate buffer (pH 7.2), and it showed a good sensitivity toward 4-NP detection even for a nanomolar concentration. The nanocomposite exhibited multi-linear ranges and 4-NP detection limit was found to be 1.2nM. The present sensor was stable and selective to 4-NP in the presence of its structural analogues such as 2-nitrophenol (2-NP), 2-aminophenol (2-AP), 3-aminophenol (3-AP), 4-aminophenol (4-AP), and 2,4-dichlorophenol (2,4-DCP). The rGO-Ag nanocomposite could be successfully applied for the determination of 4-NP in real water samples, and good recoveries were found.

Rapid dehalogenation of pesticides and organics at the interface of reduced graphene oxide–silver nanocomposite

This paper reports dehalogenation of various organohalides, especially aliphatic halocarbons and pesticides at reduced graphene oxide–silver nanocomposite (RGO@Ag). Several pesticides as well as chlorinated and fluorinated alkyl halides were chosen for this purpose. The composite and the products of degradation were characterized thoroughly by means of various microscopic and spectroscopic techniques. A sequential two-step mechanism involving dehalogenation of the target pollutants by silver nanoparticles followed by adsorption of the degraded compounds onto RGO was revealed. The composite showed unusual adsorption capacity, as high as 1534mg/g, which facilitated the complete removal of the pollutants. Irrespective of the pollutants tested, a pseudo-second-order rate equation best described the adsorption kinetics. The affinity of the composite manifested chemical differences. The high adsorption capacity and re-usability makes the composite an excellent substrate for purification of water.

Synergy of graphene oxide–silver nanocomposite and amphiphilic co-polymer F127 on antibacterial properties and permeability of PVDF membrane

Modified GO–Ag/PVDF membranes were successfully prepared based on an in situ reduction with excellent permeability, hydrophilicity, bactericidal activity.

Enhanced nonlinear optical properties of graphene oxide–silver nanocomposites measured by Z-scan technique

Enhanced (by ∼2.8) nonlinear optical property of GO–Ag nanocomposite has been reported by Z-scan technique at a visible wavelength of 532 nm. The synthesized GO–Ag nanocomposite is also displaying significant optical limiting effect.

Visual and spectrophotometric determination of mercury(II) using silver nanoparticles modified with graphene oxide

The authors describe the ultrasound-assisted synthesis of a graphene oxide-silver (GO-Ag) nanocomposite for the determination of mercury(II) (Hg(II)) using spectrophotometriy. The nanocomposite was characterized by UV-visible absorption spectra, XRD, TEM and Raman analyses. The spectral and colorimetric methods were performed for the optical determination of Hg(II). The reduction of absorption intensity with blue shift in the absorption band of Ag nanoparticles and the color change of the yellow nanocomposite solution were observed during the determination of Hg(II). The limit of detection was found to be 0.59 μM. The GO-Ag nanocomposite exhibited good selectivity toward the determination of Hg(II) in the presence of higher concentration of other environmentally relevant heavy metal ions.