Toxicity Of Ag Nanoparticles Research Articles

Exploring the interactions of Ti3C2Tx, AgNPs, and Ti3C2Tx/AgNPs with human serum albumin: Insights into conformational changes and biotoxicity reduction

Ag nanoparticles (AgNPs) are toxic and can accumulate in the human body or the environment, resulting in biotoxic effects. Ti3C2Tx, a new class of graphene-like 2D nanomaterials, is used in numerous applications due to its special physicochemical properties. There is great concern about the potential damage that this material may cause to the environment and human health. In this study, the interaction mechanisms of Ti3C2Tx, AgNPs and Ti3C2Tx/AgNPs materials with human serum albumin (HSA) were characterized using multispectral analysis and zeta potential measurements, respectively. The results showed that the effects of the three materials on the conformational changes of HSA were AgNPs > Ti3C2Tx/AgNPs > Ti3C2Tx in order. Hydrogen bonding and electrostatic interaction forces played an important role in the binding process of Ti3C2Tx and its complexes with HSA. Ag nanoparticles have a comparatively high level of biotoxicity and have a more significant effect on the conformational changes of proteins. Ti3C2Tx itself has biocompatibility and a large specific surface area. The biotoxicity of Ti3C2Tx/AgNPs complex is lower than that of AgNPs, indicating that the addition of Ti3C2Tx can reduce the biotoxicity of Ag nanoparticles, and Ti3C2Tx may be used as a carrier substance for Ag nanoparticles, which can reduce the toxicity of AgNPs while giving it unique properties similar to those of Ti3C2Tx, thus improve the biosafety of Ag nanoparticles in the application process.

Synergistic antibacterial and wound-healing applications of an imidazole-based porous organic polymer encapsulated silver nanoparticles composite

Here, a novel antibacterial agent (IM-POP-Ag) through encapsulation of Ag nanoparticles (AgNPs) into an imidazole-based porous organic polymer (IM-POP) was developed for synergistic antibacterial and wound healing. IM-POP with an ultrahigh N content of 38.42 at% was synthesized via the copolymerization of cheap and industrially mass-produced imidazole-2-carbaldehyde and melamine, via catalyst-free Schiff base chemistry, which could realize the effectively anchor of Ag on the porous skeleton (with an Ag loading of 26.01 wt%), avoiding the aggregation and reducing the toxicity of AgNPs greatly. The inherent porosity of POP realizes the effectively control on the size of AgNPs and the coordination of Ag+ changed imidazole into imidazolium, gifting the antibacterial activity to the carriers. As a result, IM-POP-Ag presented a synergistic antibacterial activity against both Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli.). For example, at the same Ag content, the survival rates of E. coli and S. aureus in response to 200 μg mL−1 IM-POP-Ag (equivalent to 50 μg mL−1 AgNPs) were 3.44 ± 0.21% and 6.34 ± 0.40%, respectively, far outperforming that of bare AgNPs (12.19 ± 0.54% and 20.20 ± 0.19%). In vivo experiments on mice testified IM-POP-Ag could significantly promote the healing rate of infected wounds which could facilitate the growth of vessel and hair follicle, accelerating epithelialization. Hence, this novel and mass-produced antibacterial agent provides a new strategy and theoretical basis for the application of AgNPs with higher efficacy and biocompatibility in the near future.

Wastewater-Aged Silver Nanoparticles in Single and Combined Exposures with Titanium Dioxide Affect the Early Development of the Marine Copepod Tisbe battagliai.

In this study, the effects of aged Ag and TiO2 nanoparticles (NPs), individually and as a mixture, in wastewater relative to their pristine counterparts on the development of the copepod nauplii (Tisbe battagliai) were investigated. NP behavior in synthetic wastewater and seawater was characterized during aging and exposure. A delayed development and subsequent mortality were observed after 6 days of exposure to aged Ag NPs, with a twofold decrease in EC50 (316 μg/L) compared to pristine NPs (EC50 640 μg/L) despite the similar dissolved Ag concentrations measured for aged and pristine Ag NPs (441 and 378 μg/L, respectively). In coexposures with TiO2 NPs, higher dissolved Ag levels were measured for aged NPs (238.3 μg/L) relative to pristine NPs (98.57 μg/L). Coexposure resulted in a slight decrease (15%) in the Ag NP EC50 (270 μg/L) with a 1.9-fold increase in the Ag NP retained within the organisms after depuration (2.82% retention) compared to Ag NP single exposures as measured with sp-ICP-MS, suggesting that the particles are still bioavailable despite the heteroaggregation observed between Ag, Ti NPs, and wastewater components. This study shows that the presence of TiO2 NPs can affect the stability and toxicity of Ag NPs in complex media that cannot be predicted solely based on ionic, total, or nanoparticulate concentrations, and the need for studying NP interactions in more complex matrices is highlighted.

Extraction Method Development for Quantitative Detection of Silver Nanoparticles in Environmental Soils and Sediments by Single Particle Inductively Coupled Plasma Mass Spectrometry.

For understanding the environmental behavior and toxicity of Ag nanoparticles (Ag-NPs), a quantitative method for characterizing the AgNPs in soils and sediments is urgently needed. In this study, we validated a previously developed extraction method by optimizing the extraction of silver nanoparticles from soil and sediment samples to which engineered AgNPs had been added. The samples were analyzed by single particle inductively coupled plasma mass spectrometry (SP-ICP-MS). Initially, different extraction conditions were evaluated to validate the optimal extraction procedure. Then the optimal extraction procedure was applied to environmental soil and sediment samples spiked with AgNPs. The extraction data for Ag-NPs with sizes below 30 nm was not shown due to the particle size detection limit of the SP-ICP-MS method (∼20 nm). The number concentrations of Ag particles extracted from different environmental soils and sediments matrices were in the range of (12 ± 1-23 ± 1) × 107 particles/g soil. Similarly, 53.4-100.0% of the particulate Ag mass was recovered. For the relatively low Ag mass recovery of Guiyu agricultural soil, the Ag mass recovery shows great improvement (from 53.4 to 105.8%) by the soil dilution using SiO2. The optimal method was validated to be feasible for extracting Ag-NPs from environmental soils and sediments, except for the soil with high soil organic matter (SOM) content. The SiO2 dilution of soil provides a promising way to promote the extraction of Ag-NPs in soil (or sediment) with high SOM content, which could further promote the study on the environmental behavior and toxicity of Ag-NPs in soil and sediment environment.

Molecular Responses in THP-1 Macrophage-Like Cells Exposed to Diverse Nanoparticles.

In the body, engineered nanoparticles (NPs) may be recognized and processed by immune cells, among which macrophages play a crucial role. We evaluated the effects of selected NPs [NM-100 (TiO2), NM-110 (ZnO), NM-200 (SiO2), and NM-300 K (Ag)] on THP-1 macrophage-like cells. The cells were exposed to subcytotoxic concentrations of NPs (1–25 µg/mL) and the expression of immunologically relevant genes (VCAM1, TNFA, CXCL8, ICAM1, CD86, CD192, and IL1B) was analyzed by RT-qPCR. The expression of selected cytokines, growth factors and surface molecules was assessed by flow cytometry or ELISA. Generation of reactive oxygen species and induction of DNA breaks were also analyzed. Exposure to diverse NPs caused substantially different molecular responses. No significant effects were detected for NM-100 treatment. NM-200 induced production of IL-8, a potent attractor and activator of neutrophils, growth factors (VEGF and IGF-1) and superoxide. NM-110 triggered a proinflammatory response, characterized by the activation of transcription factor NF-κB, an enhanced production of proinflammatory cytokines (TNF-α) and chemokines (IL-8). Furthermore, the expression of cell adhesion molecules VCAM-1 and ICAM-1 and hepatocyte growth factor (HGF), as well as superoxide production and DNA breaks, were affected. NM-300 K enhanced IL-8 production and induced DNA breaks, however, it decreased the expression of chemokine receptor (CCR2) and CD86 molecule, indicating potential immunosuppressive activity. The toxicity of ZnO and Ag NPs was probably caused by their intracellular dissolution, as indicated by transmission electron microscopy imaging. The observed effects in macrophages might further influence both innate and adaptive immune responses by promoting neutrophil recruitment via IL-8 release and enhancing the adhesion and stimulation of T cells by VCAM-1 and ICAM-1 expression.

Cyanidin chloride modestly protects Caco-2 cells from ZnO nanoparticle exposure probably through the induction of autophagy

Recent studies suggest that phytochemicals, as part of the food matrix, might alter the toxicity of nanoparticles (NPs); however, relatively few studies have investigated the impact of anthocyanidins on the toxicity of NPs to cells lining the gastrointestinal tract. Therefore, this study used cyanidin chloride (CC) as the model for anthocyanidins and investigated the effects of CC on the toxicity of ZnO or Ag NPs to Caco-2 cells. Exposure to ZnO but not Ag NPs significantly induced cytotoxicity. The presence of CC, but not its analog quercetin (Qu), modestly protected Caco-2 cells from ZnO NP exposure. However, the intracellular superoxide, Zn ions, or release of interleukin-8 after ZnO NP exposure were not significantly affected by the presence of CC. Rather, CC promoted the expression of autophagic genes ATG5, ATG7, and BECN1 as well as the ratio of LC3-II/I after exposure to ZnO NPs. Meanwhile, the presence of autophagic inhibitors (chloroquine, NH4Cl, bafilomycin A1) significantly promoted the cytotoxicity of ZnO NPs and inhibited the cytoprotective effects of CC. In conclusion, these data suggest that CC could modestly protect Caco-2 cells from ZnO NP exposure, probably through the induction of autophagy.

A review of cardiovascular toxicity of TiO2, ZnO and Ag nanoparticles (NPs).

To ensure the safe use of nanoparticles (NPs) in modern society, it is necessary and urgent to assess the potential toxicity of NPs. Cardiovascular system is required for the systemic distribution of NPs entering circulation. Therefore, the adverse cardiovascular effects of NPs have gained extensive research interests. Metal based NPs, such as TiO2, ZnO and Ag NPs, are among the most popular NPs found in commercially available products. They may also have potential applications in biomedicine, which could increase their contact with cardiovascular systems. This review aimed at providing an overview about the adverse cardiovascular effects of TiO2, ZnO and Ag NPs. We discussed about the bio-distribution of NPs following different exposure routes. We also discussed about the cardiovascular toxicity of TiO2, ZnO and Ag NPs as assessed by in vivo and in vitro models. The possible mechanisms and contribution of physicochemical properties of metal based NPs were also discussed.

Ecotoxicity of different-shaped silver nanoparticles: Case of zebrafish embryos

As the worldwide application of silver nanomaterials in commercial products increases every year, and concern about the environmental risks of such nanoparticles also grows. A clear understanding of how different characteristics of nanoparticles contribute in their toxic behavior to organisms are imperative for predicting and control nanotoxicity. Within our research, we investigated the toxic effect of two types of silver nanoparticles (spherical and flat Ag nanoparticles) on zebrafish (Danio rerio) embryos. Particular interest was paid to proper characterization of Ag nanoparticles initially and during the experiment. A proper test medium was found and used for ecotoxicity evaluation. The behavior of flat silver nanoparticles with respect to embryos of zebrafish was analyzed and compared to the ecotoxicity of silver ionic form (AgNO3). Both types of nanoparticles showed a more pronounced toxic effect to Danio rerio embryos than silver ions (AgNO3), while silver nanoplates were more harmful than Ag nanospheres. While previous investigations showed that toxicity of Ag nanoparticles can be explained by the presence of Ag+ in solution of silver nanoparticles, our results demonstrate that the harmful effects of nanosilver may be associated with silver nanoparticles themselves than with ionic silver released into solution.

Silver nanoparticle antimicrobial activity explained by membrane rupture and reactive oxygen generation

Silver nanoparticles are widely used as antimicrobial compounds based on empirical observations. However, there is few knowledge on the mechanism ruling the antimicrobial activity and toxicity of Ag nanoparticles. Here, we investigated this mechanism. Nano-Ag was synthesised by thermal co-reduction. Mutagenicity analysis was performed using Salmonella typhimurium histidine auxotrophic strains TA 98 and TA 100 at nano-silver concentrations of 100 to 500 µg per plate. Dose-dependent analysis for reactive oxygen species generation has been performed using 2,7-dichlorofluorescein diacetate dye. Membrane integrity has been analyzed at 260 nm, before and after treatment. We also used scanning electron microscopy, membrane permeabilization test, and superoxide formation determinations. Results show that the average particle size of Ag nanoparticle is 60.4 ± 3.8 nm. The minimum inhibitory concentration of Ag nanoparticles for E.coli is 30 µg/mL; the minimum bactericidal concentration is 40 µg/mL. Ames mutagenicity tests showed negative results, which may be explained by the antimicrobial activity of nano-silver. Bacterial inner wall were indeed ruptured, and cytoplasmic content was released after 5 min of treatment in a dose-dependent manner. We thus propose that reactive oxygen generation and alteration of membrane integrity and permeability are the major mechanism of antimicrobial activity of nano-silver.

Toxicological Effects of Caco-2 Cells Following Short-Term and Long-Term Exposure to Ag Nanoparticles.

Extensive utilization increases the exposure of humans to Ag nanoparticles (NPs) via the oral pathway. To comprehensively address the action of Ag NPs to the gastrointestinal systems in real situations, i.e., the long-term low-dose exposure, we evaluated and compared the toxicity of three Ag NPs (20–30 nm with different surface coatings) to the human intestine cell Caco-2 after 1-day and 21-day exposures, using various biological assays. In both the short- and long-term exposures, the variety of surface coating predominated the toxicity of Ag NPs in a descending order of citrate-coated Ag NP (Ag-CIT), bare Ag NP (Ag-B), and poly (N-vinyl-2-pyrrolidone)-coated Ag NP (Ag-PVP). The short-term exposure induced cell growth inhibition and death. The cell viability loss appeared after cells were exposed to 0.7 μg/mL Ag-CIT, 0.9 μg/mL Ag-B or >1.0 μg/mL Ag-PVP for 24 h. The short-term and higher-dose exposure also induced reactive oxygen species (ROS) generation, mitochondrial damage, cell membrane leakage, apoptosis, and inflammation (IL-8 level). The long-term exposure only inhibited the cell proliferation. After 21-day exposure to 0.4 μg/mL Ag-CIT, the cell viability dropped to less than 50%, while cells exposed to 0.5 μg/mL Ag-PVP remained normal as the control. Generally, 0.3 μg/mL is the non-toxic dose for the long-term exposure of Caco-2 cells to Ag NPs in this study. However, cells presented inflammation after exposure to Ag NPs with the non-toxic dose in the long-term exposure.

Determination of inequable fate and toxicity of Ag nanoparticles in a Phanerochaete chrysosporium biofilm system through different sulfide sources

Cysteine and Na2S induced different distributions and toxicities of AgNP in biofilms.

Physicochemical transformation and algal toxicity of engineered nanoparticles in surface water samples

Most studies on the behavior and toxicity of engineered nanoparticles (NPs) have been conducted in artificial water with well-controlled conditions, which are dramatically different from natural waters with complex compositions. To better understand the fate and toxicity of NPs in the natural water environment, physicochemical transformations of four NPs (TiO2, ZnO, Ag, and carbon nanotubes (CNTs)) and their toxicities towards a unicellular green alga (Chlorella pyrenoidosa) in four fresh water and one seawater sample were investigated. Results indicated that water chemistry had profound effects on aggregation, dissolution, and algal toxicity of the NPs. The strongest homoaggregation of the NPs was associated with the highest ionic strength, but no obvious correlation was observed between the homoaggregation of NPs and pH or dissolved organic matter content of the water samples. The greatest dissolution of ZnO NPs also occurred in seawater with the highest ionic strength, while the dissolution of Ag NPs varied differently from ZnO NPs. The released Zn2+ and especially Ag+ mainly accounted for the algal toxicity of ZnO and Ag NPs, respectively. The NP-cell heteroagglomeration occurred generally for CNTs and Ag NPs, which contributed to the observed nanotoxicity. However, there was no significant correlation between the observed nanotoxicity and the type of NP or the water chemistry. It was thus concluded that the physicochemical transformations and algal toxicities of NPs in the natural water samples were caused by the combined effects of complex water quality parameters rather than any single influencing factor alone. These results will increase our knowledge on the fate and effects of NPs in the aquatic environment.

Green synthesis of silver nanoparticles for selective toxicity towards cancer cells.

Therapeutic applications of nanoparticles (NPs) are rapidly increasing for their utility in medicine, especially cancer therapy. The present study investigated the green synthesis of silver NPs (Ag NPs) of 10 nm size using Sargassum vulgare and its preferential ability to kill cancerous human myeloblastic leukemic cells HL60 and cervical cancer cells HeLa as compared with normal peripheral blood mononuclear cells. DNA fragmentation study and annexin V marker fluorescence-activated cell sorting (FACS) analysis revealed the Ag NP-induced cell death is through apoptosis. Transmission electron micrographs have showed the endocytosis of Ag NPs into the nucleus. Ag NPs inhibited the lipid peroxidation-induced reactive oxygen species generation, thus preventing the irradiation-related carcinogenesis. This study suggested that a mechanism underlying the toxicity of Ag NPs towards cancer cells is due to DNA damage and apoptosis. The authors' findings revealed the potential utility of as-prepared Ag NPs in the treatment of cancer as prophylactic agent with antioxidant property and chemotherapeutic agent for their selective toxicity to cancer cells.

In vitro and in vivo study of hazardous effects of Ag nanoparticles and Arginine-treated multi walled carbon nanotubes on blood cells: application in hemodialysis membranes.

One of the novel applications of the nanostructures is the modification and development of membranes for hemocompatibility of hemodialysis. The toxicity and hemocompatibility of Ag nanoparticles and arginine-treated multiwalled carbon nanotubes (MWNT-Arg) and possibility of their application in membrane technology are investigated here. MWNT-Arg is prepared by amidation reactions, followed by characterization by FTIR spectroscopy, Raman spectroscopy, and thermogravimetric analysis. The results showed a good hemocompatibility and the hemolytic rates in the presence of both MWNT-Arg and Ag nanoparticles. The hemolytic rate of Ag nanoparticles was lower than that of MWNT-Arg. In vivo study revealed that Ag nanoparticle and MWNT-Arg decreased Hematocrit and mean number of red blood cells (RBC) statistically at concentration of 100 µg mL(-1) . The mean decrease of RBC and Hematocrit for Ag nanoparticles (18% for Hematocrit and 5.8 × 1,000,000/µL) was more than MWNT-Arg (20% for Hematocrit and 6 × 1000000/µL). In addition, MWNT-Arg and Ag nanoparticles had a direct influence on the White Blood Cell (WBC) drop. Regarding both nanostructures, although the number of WBC increased in initial concentration, it decreased significantly at the concentration of 100 µg mL(-1) . It is worth mentioning that the toxicity of Ag nanoparticle on WBC was higher than that of MWNT-Arg. Because of potent antimicrobial activity and relative hemocompatibility, MWNT-Arg could be considered as a new candidate for biomedical applications in the future especially for hemodialysis membranes.

Effect of toxicity of Ag nanoparticles on SERS spectral variance of bacteria

Ag nanoparticles (NPs) have been extensively utilized in surface-enhanced Raman scattering (SERS) spectroscopy for bacterial identification. However, Ag NPs are toxic to bacteria. Whether such toxicity can affect SERS features of bacteria and interfere with bacterial identification is still unknown and needed to explore. Here, by carrying out a comparative study on non-toxic Au NPs with that on toxic Ag NPs, we investigated the influence of nanoparticle concentration and incubation time on bacterial SERS spectral variance, both of which were demonstrated to be closely related to the toxicity of Ag NPs. Sensitive spectral alterations were observed on Ag NPs with increase of NPs concentration or incubation time, accompanied with an obvious decrease in number of viable bacteria. In contrast, SERS spectra and viable bacterial number on Au NPs were rather constant under the same conditions. A further analysis on spectral changes demonstrated that it was cell response (i.e. metabolic activity or death) to the toxicity of Ag NPs causing spectral variance. However, biochemical responses to the toxicity of Ag were very different in different bacteria, indicating the complex toxic mechanism of Ag NPs. Ag NPs are toxic to a great variety of organisms, including bacteria, fungi, algae, protozoa etc., therefore, this work will be helpful in guiding the future application of SERS technique in various complex biological systems.

Significance of physicochemical and uptake kinetics in controlling the toxicity of metallic nanomaterials to aquatic organisms

With the extensive applications of metallic-based nanomaterials (MNs), concerns are growing of their potential impact on aquatic organisms. Unlike traditional metal pollutants, MNs have different surface properties and compositions, which may modify their impact on aquatic environments as well as their bioavailability to aquatic organisms. Kinetic processes of MNs, such as dissolution, stabilization, aggregation, and sedimentation, are important in determining their bioavailability and subse- quent toxicity to aquatic organisms. Among all of the physicochemical kinetics, the dissolution of MNs attracts the most attention, due to their potential toxicity generated by dissolved ions. This review summarizes the dissolution behavior of three common MNs, i.e., ZnO nanoparticles (ZnO-NPs), Ag nanoparticles (Ag-NPs), and TiO2 nanoparticles (TiO2-NPs), in toxicological studies. A kinetic model was developed to evaluate the contribution of dissolved ion on the total MN accumulation. Finally, toxicological data of the MNs to algae, zooplankton, and fish are summarized and interpreted based on their kinetics. Different dissolution rates were observed for ZnO-NPs, Ag-NPs, and TiO2-NPs, and their solubility also varied during different toxicological studies, leading to a variable but increasing waterborne ion concentration during exposure. The bioavailability of these MNs and corresponding ions also varied for different aquatic organisms (e.g., algae, zooplankton, and fish). Specifically, the MNs appeared to be more bioavailable to daphnids, rendering a minor contribution of ion during short-term exposure. Generally, dissolved ion contributed partially to toxicity of ZnO-NPs and Ag-NPs, while the toxicity of TiO2-NPs was mainly due to the generated reactive oxygen species (ROS). Additionally, the role of dissolved ion in both MN bioaccumulation and toxicity intensified during chronic ex- posure as a result of dissolution, thus it is critical to monitor the dissolution of MNs in toxicological studies. This review empha- sizes the importance of integrating physicochemical kinetics and uptake kinetics in evaluating the bioavailability and toxicity of both MNs and dissolved ions.

Phytotoxicity of silver nanoparticles to cucumber (Cucumis sativus) and wheat (Triticum aestivum)

The increasing release of silver (Ag) nanoparticles (NPs) into the environment highlights the importance of exploring the interactions between Ag NPs and plants, which are the basis of most ecosystems. In this study, two plant species, Cucumis sativus L. (cucumber) and Triticum aestivum L. (wheat) were exposed to Ag NPs and Ag+ (added as AgNO3) at the germination and vegetative growth stages. Above certain concentrations, Ag NPs and Ag+ were toxic to the two plants. However, stimulatory effects were observed on root elongation for the cucumbers that were exposed to Ag NPs at concentrations below 200 mg/L, and Ag+ at concentrations below 5 mg/L. The two plants were more susceptible to the toxicity of Ag NPs at the vegetative growth stage than the germination stage. Ag was accumulated in the roots and was subsequently translocated to the shoots after the exposure to Ag NPs. To assess the role of released Ag+, we measured the dissolution of Ag NPs in exposure solutions. About 0.03% and 0.01% of Ag NPs were dissolved into a hydroponic solution at the germination stage for cucumber and wheat, respectively; while 0.17% and 0.06% at the vegetative period for cucumber and wheat, respectively. Cysteine, a strong chelating ligand of Ag+, could completely eliminate the effects of Ag NPs on cucumber and wheat, suggesting that the phytotoxicity of Ag NPs was possibly caused by the release of Ag+.

Effects of physiochemical properties of test media on nanoparticle toxicity to Daphnia magna Straus.

The physicochemical property of standard test media significantly influenced the aggregation and dissolution of Ag, CuO and ZnO nanoparticles (NPs) and the toxicity of the NPs to Daphnia magna. For all the NPs, the highest amount of metal ions was released from the ISO medium, whereas acute toxicity to D. magna was highest in the moderately hard water medium (EC50 = 4.94, 980, and 1,950 μg L(-1) for Ag, CuO, and ZnO, respectively). By comparing EC50 values based on the total and dissolved concentrations of NPs with those of metal salt solutions, we found that both particulate and dissolved fractions were likely responsible for the toxicity of Ag NPs, whereas the dissolved fraction mostly contributed to the toxicity of CuO and ZnO NPs.

Differential Effect of Solar Light in Increasing the Toxicity of Silver and Titanium Dioxide Nanoparticles to a Fish Cell Line and Zebrafish Embryos

The increasing use of silver (Ag) and titanium dioxide (TiO2) nanoparticles (NPs) in consumer products and their inevitable seepage into the environment prompted us to investigate their potential toxicity to a fish cell line (BF-2) and zebrafish embryos under dark and Simulated Solar Light (SSL) exposure conditions. Using high throughput screening (HTS) platforms, we showed that the oxidative stress-dependent cytotoxicity and embryonic toxicity of NPs were significantly increased upon exposure to SSL. While, the toxicity of TiO2 NPs under SSL exposure could be explained by hydroxyl radical generation, the enhanced toxicity of Ag NPs under SSL exposure was due to surface oxidation and physicochemical modification of Ag NPs and shedding of Ag+, leading to an increased bioavailability of silver. Our observations that solar light could induce physicochemical transformation of TiO2 and Ag NPs and enhance their toxic potential emphasizes the need for conducting future toxicity studies under environmentally relevant exposure conditions to guide decision making on the safe handling of NPs.

Synthesis and Characterization Silver, Zinc Oxide and Hybrid Silver/Zinc Oxide Nanoparticles for Antimicrobial Applications

Silver ( Ag ) and zinc oxide ( ZnO ) are well known for both antimicrobial and pro-healing properties. Here, we present a novel method to synthesize Ag and ZnO nanoparticles (NPs), as well as hybrid Ag / ZnO NPs using a custom, temperature controlled microwave assisted technique. Microwave synthesis has been shown not only to enhance the rate of chemical reactions, but also in some cases to give higher product yields over thermal heating. The as-synthesized NPs were characterized by X-ray diffraction (XRD) to study the crystalline structure, composition and purity. Transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS) was used to study particle size, shape, composition and morphology. These results indicated that the as-prepared Ag NPs are spherical in shape and ~ 20 nm in sizes. The ZnO NPs are typically rod shaped and the particle sizes are ~ 20 nm in width and 100 nm in length. These NPs were tested for antibacterial and/or antifungal properties using disc diffusion assays. Results show microwave synthesized NPs inhibit growth of S. aureus, E. coli and C. albicans at 50 μ g/mL treatment concentration. Ag NPs were most effective in inhibiting bacterial and fungal growth at the concentrations tested followed by hybrid Ag / ZnO and ZnO nanoparticles. These results also suggest that the hybridization of ZnO to Ag NPs may reduce the toxicity of Ag NPs. Further studies are needed to understand the functional interaction between the two types of NPs and to improve their ability for biological or biomedical application.