Highly Biocompatible Nanoparticles of Au@Fluorescent Polymers as Novel Contrast Agent for In Vivo Bimodality NIR Fluorescence/CT Imaging

In this work, one kind of biocompatible and all-in-one dual-modal nanoprobe, based on Au nanoparticles and NIR emissive semiconducting fluorescence polymers, was developed by the one-step solvent-mediated self-assembly method for in vivo X-ray computed tomography (CT) and fluorescence bioimaging for the first time. After preparation, a series of comprehensive evaluations were performed, and the nanoprobe exhibited smart size and modification, good compatibility, inducement of autophagy, long blood circulation, unconspicuous in vivo toxicity, and excellent fluorescence/CT imaging effects. Overall, the studies in this work assuredly indicate that the synthesized Au@FP nanoparticles as a noninvasive contrast agent is suitable for in vivo fluorescence/X-ray CT bimodality biomedical imaging and diagnosis.

Synthesis, Photothermal Effect and Cytotoxicity of Fe₃O₄@Au Nanocomposites

It is currently a very active research area to develop multifunctional nanocomposites (NCs) which integrate the novel properties from various nanomaterials for multimodal imaging and simultaneous therapy. These theranostic nanoplatforms can provide complementary information from each imaging modality for accurate diagnosis and, at the same time, afford an imaging-guided focused tumor therapy. Among them, core/shell Fe₃O₄@Au NCs have attracted wide attention due to their unique advantages in magnetic targeting, multimodal imaging and photothermal therapy. This study developed a layer-by-layer assembling approach to synthesize Fe₃O₄@Au NCs with high photothermal conversion efficiency. The as-synthesized NCs showed significant photothermal ablation capability to HeLa cells in vitro under near infrared laser irradiation. To ensure the safety for medical applications, the bio-effects of Fe₃O₄@Au NCs on RAW264.7 cells were carefully assessed, in terms of cell viability, oxidative stress and apoptosis. We have demonstrated that Fe₃O₄@Au NCs had good biocompatibility in RAW264.7 cells and no significant cytotoxicity was found. Therefore, the Fe₃O₄@Au NCs synthesized in this study have great potential as an ideal candidate for CT/MR imaging and photothermal therapy.

Nano-eco toxicity study of gold nanoparticles on aquatic organism Moina macrocopa: As new versatile ecotoxicity testing model

In the field of nanoecotoxicology, very few reports have focused on biochemical changes in non-target organisms after nanoexposure. A less explored aquatic non-target crustacean, Moina macrocopa, was used in the present study to analyze toxicity effects of gold nanoparticles (AuNPs), an emerging nanomaterial. AuNPs was fabricated using tannic acid and were 29 ± 2 nm in size. The 48 h LC₅₀ value of AuNPs was 14 ± 0.14 mg/L against M. macrocopa. The sub-lethal exposure of M. macrocopa juveniles to AuNPs (1.47 and 2.95 mg/L) decreased the activities of acetyl cholinesterase and digestive enzymes (trypsin and amylase). A concentration dependant increase in the activities of antioxidant enzymes such as catalase, superoxide dismutase and glutathione S-transferase suggested the generation of oxidative stress in M. macrocopa after AuNPs exposure. Changes in enzyme activity can be utilized as biomarker(s) for early detection of nanoparticle contamination in aquatic habitat. AuNPs accumulation in gut of M. macrocopa increased the metal bio burden (11 mg/L) and exhibited inhibitory action on digestive enzymes. Complete depuration of AuNPs was not observed after transferring nano-exposed M. macrocopa to normal medium without AuNPs. AuNPs tended to adhere on external body parts such as setae, carapace of M. macrocopa which interfered with swimming activity and also changed the behavioral pattern. AuNPs underwent agglomeration in the medium used for maintenance of M. macrocopa. As nanomaterials are emerging pollutants in aquatic systems, the present work highlights the hazardous effect of AuNPs and development of enzymatic biomarkers to curtail it at community level.

Catalase-mimetic gold nanoparticles inhibit the antagonistic action of Lactobacillus gasseri toward foodborne enteric pathogens in associative cultures

Gold nanoparticles (AuNPs) have been previously shown to induce gut dysbiosis during colitis in mice, but the underlying mechanism is not clear yet. Here, we evaluated the effects of AuNPs (5 nm diameter, coated with tannic acid, polyvinylpyrrolidone or citrate) on H₂O₂ accumulation and pathogen antagonization by an intestinal strain of Lactobacillus gasseri under aerobic cultural conditions. AuNPs (0.65 μg/mL) reduced over 50% of H₂O₂ accumulation by L. gasseri, and significantly inhibited the antagonistic action of L. gasseri on growth of four foodborne enteric pathogens, i.e. Salmonella enterica serovar Typhimurium, Escherichia coli, Listeria monocytogenes, and Staphylococcus aureus in associative cultures.

Genotoxicity of gold nanoparticles in the gilthead seabream (Sparus aurata) after single exposure and combined with the pharmaceutical gemfibrozil

Due to their diverse applications, gold nanoparticles (AuNPs) are expected to increase of in the environment, although few studies are available on their mode of action in aquatic organisms. The genotoxicity of AuNPs, alone or combined with the human pharmaceutical gemfibrozil (GEM), an environmental contaminant frequently detected in aquatic systems, including in marine ecosystems, was examined using gilthead seabream erythrocytes as a model system. Fish were exposed for 96 h to 4, 80 and 1600 μg L^-1 of 40 nm AuNPs with two coatings - citrate or polyvinylpyrrolidone; GEM (150 μg L^-1); and a combination of AuNPs and GEM (80 μg L^-1 AuNPs + 150 μg L^-1 GEM). AuNPs induced DNA damage and increased nuclear abnormalities levels, with coating showing an important role in the toxicity of AuNPs to fish. The combined exposures of AuNPs and GEM produced an antagonistic response, with observed toxic effects in the mixtures being lower than the predicted. The results raise concern about the safety of AuNPs and demonstrate interactions between them and other contaminants.

Evaluation of in vitro effect of selected contact lens solutions conjugated with nanoparticles in terms of preventive approach to public health risk generated by Acanthamoeba strains

INTRODUCTION

Various Acanthamoeba species are free-living organisms widely distributed in the human environment. Amphizoic amoebae as facultative parasites may cause vision-threatening eye disease - Acanthamoeba keratitis, mostly among contact lens wearers. As the number of cases is increasing, and applied therapy often unsuccessful, proper hygienic measures and effective contact lenses disinfection are crucial for the prevention of this disease. Available contact lens solutions are not fully effective against amphizoic amoebae; there is a need to enhance their disinfecting activity to prevent amoebic infections. The use of developing nanotechnology methods already applied with success in the prevention, diagnostic and therapy of other infectious diseases might be helpful regarding amoebic keratitis. This study assesses the in vitro effect of selected contact lens solutions conjugated with nanoparticles against Acanthamoeba trophozoites.

MATERIAL AND METHODS

Three selected contact lens solutions conjugated with silver and gold nanoparticles in concentration of 0.25-2.5 ppm were used in vitro against the axenically cultured ATCC 30010 type Acanthamoeba castellanii strain. The anti-amoebic efficacy was examined based on the oxido-reduction of AlamarBlue. The cytotoxicity tests based on the measurement of lactate dehydrogenase (LDH) activity were performed using a fibroblast HS-5 cell line.

RESULTS

Enhancement of the anti-amoebic activity of contact lens solutions conjugated with selected nanoparticles expressed in the dose dependent amoebic growth inhibition with a low cytotoxicity profile was observed.

CONCLUSIONS

Results of the study showed that conjugation of selected contact lens solutions with silver nanoparticles might be a promising approach to prevent Acanthamoeba keratitis among contact lens users.

The development of a hairless phenotype in barley roots treated with gold nanoparticles is accompanied by changes in the symplasmic communication

Uptake of water and nutrients by roots affects the ontogenesis of the whole plant. Nanoparticles, e.g. gold nanoparticles, have a broad range of applications in many fields which leads to the transfer of these materials into the environment. Thus, the understanding of their impact on the growth and development of the root system is an emerging issue. During our studies on the effect of positively charged gold nanoparticles on the barley roots, a hairless phenotype was found. We investigated whether this phenotype correlates with changes in symplasmic communication, which is an important factor that regulates, among others, differentiation of the rhizodermis into hair and non-hair cells. The results showed no restriction in symplasmic communication in the treated roots, in contrast to the control roots, in which the trichoblasts and atrichoblasts were symplasmically isolated during their differentiation. Moreover, differences concerning the root morphology, histology, ultrastructure and the cell wall composition were detected between the control and the treated roots. These findings suggest that the harmful effect of nanoparticles on plant growth may, among others, consist in disrupting the symplasmic communication/isolation, which leads to the development of a hairless root phenotype, thus limiting the functioning of the roots.

Cytotoxicity of Ag, Au and Ag-Au bimetallic nanoparticles prepared using golden rod (Solidago canadensis) plant extract

Production and use of metallic nanoparticles have increased dramatically over the past few years and design of nanomaterials has been developed to minimize their toxic potencies. Traditional chemical methods of production are potentially harmful to the environment and greener methods for synthesis are being developed in order to address this. Thus far phytosynthesis have been found to yield nanomaterials of lesser toxicities, compared to materials synthesized by use of chemical methods. In this study nanoparticles were synthesized from an extract of leaves of golden rod (Solidago canadensis). Silver (Ag), gold (Au) and Ag-Au bimetallic nanoparticles (BNPs), synthesized by use of this "green" method, were evaluated for cytotoxic potency. Cytotoxicity of nanomaterials to H4IIE-luc (rat hepatoma) cells and HuTu-80 (human intestinal) cells were determined by use of the xCELLigence real time cell analyzer. Greatest concentrations (50 µg/mL) of Ag and Ag-Au bimetallic were toxic to both H4IIE-luc and HuTu-80 cells but Au nanoparticles were not toxic. BNPs exhibited the greatest toxic potency to these two types of cells and since AuNPs caused no toxicity; the Au functional portion of the bimetallic material could be assisting in uptake of particles across the cell membrane thereby increasing the toxicity.

Metal accumulation, biochemical and behavioral responses on the Mediterranean clams Ruditapes decussatus exposed to two photocatalyst nanocomposites (TiO2 NPs and AuTiO2NPs)

Nanoparticle decoration with noble metal represents a promising alternative to improve their photocatalytic and photovoltaic properties. However, toxicity can be influenced by such modification, as the bioavailability of these substances may be influenced. To understand how decoration influences the NP impacts in marine ecosystems, we exposed suspension-feeding clams, Ruditapes decussatus, to two photocatalyst nanocomposites, TiO₂ NPs and AuTiO₂ NPs, over 2 concentrations, 50 μg L^-1and 100 μg L^-1, in a laboratory experiment. Accumulation of Au and Ti in gills and digestive gland was noted in clams after exposure to TiO₂ NPs and AuTiO₂ NPs using inductively coupled plasma optic emission spectroscopy (ICP-OES). TiO₂ and AuTiO₂ NPs alter the behavior of the clams Ruditapes decussatus by reducing filtration and respiration rates. Furthermore, the highest concentration of TiO₂NPs induces an overproduction of H₂O₂ in gills and digestive gland and NO production only in gills. Superoxide dismutase (SOD), Catalase (CAT), Glutathione-S-transferase (GST) and acetylcholinesterase (AChE) activities were induced in gills and digestives gland in concentration and nanocomposite type dependent manner. Decorated form presented higher Malondialdehyde (MDA) levels in gills and digestive gland than the undecorated form, suggesting different mechanisms of action that may be mediated through oxidative stress. In conclusion, the considered parameters could represent reliable biomarkers for the assessment of NP toxicity on R. decussatus as biological biomonitoring model. In addition, based on the obtained results, nanoparticle decoration influences the toxicity of metal nanoparticles in marine organism.

Bioaccumulation of polystyrene nanoplastics and their effect on the toxicity of Au ions in zebrafish embryos

As nano- and micro-sized plastics accumulate in the environment and the food chain of animals, including humans, it is imperative to assess the effects of nanoplastics in living organisms in a systematic manner, especially because of their ability to adsorb potential toxicants such as pollutants, heavy metals, and organic macromolecules that coexist in the environment. Using the zebrafish embryo as an animal model, we investigated the bioaccumulation and in vivo toxicity of polystyrene (PS) nanoplastics individually or in combination with the Au ion. We showed that smaller PS nanoplastics readily penetrated the chorion and developing embryos and accumulated throughout the whole body, mostly in lipid-rich regions such as in yolk lipids. We also showed that PS nanoplastics induced only marginal effects on the survival, hatching rate, developmental abnormalities, and cell death of zebrafish embryos but that these effects were synergistically exacerbated by the Au ion in a dose- and size-dependent manner. Such exacerbation of toxicity was well correlated with the production of reactive oxygen species and the pro-inflammatory responses synergized by the presence of PS, supporting the combined toxicity of PS and Au ions. The synergistic effect of PS on toxicity appeared to relate to mitochondrial damage as determined by ultrastructural analysis. Taken together, the effects of PS nanoplastics were marginal but could be a trigger for exacerbating the toxicity induced by other toxicants such as metal ions.

Bioaccumulation of polystyrene nanoplastics and their effect on the toxicity of Au ions in zebrafish embryos

As nano- and micro-sized plastics accumulate in the environment and the food chain of animals, including humans, it is imperative to assess the effects of nanoplastics in living organisms in a systematic manner, especially because of their ability to adsorb potential toxicants such as pollutants, heavy metals, and organic macromolecules that coexist in the environment. Using the zebrafish embryo as an animal model, we investigated the bioaccumulation and in vivo toxicity of polystyrene (PS) nanoplastics individually or in combination with the Au ion. We showed that smaller PS nanoplastics readily penetrated the chorion and developing embryos and accumulated throughout the whole body, mostly in lipid-rich regions such as in yolk lipids. We also showed that PS nanoplastics induced only marginal effects on the survival, hatching rate, developmental abnormalities, and cell death of zebrafish embryos but that these effects were synergistically exacerbated by the Au ion in a dose- and size-dependent manner. Such exacerbation of toxicity was well correlated with the production of reactive oxygen species and the pro-inflammatory responses synergized by the presence of PS, supporting the combined toxicity of PS and Au ions. The synergistic effect of PS on toxicity appeared to relate to mitochondrial damage as determined by ultrastructural analysis. Taken together, the effects of PS nanoplastics were marginal but could be a trigger for exacerbating the toxicity induced by other toxicants such as metal ions.

High time resolution and high signal-to-noise monitoring of the bacterial growth kinetics in the presence of plasmonic nanoparticles

BACKGROUND

Emerging concepts for designing innovative drugs (i.e., novel generations of antimicrobials) frequently include nanostructures, new materials, and nanoparticles (NPs). Along with numerous advantages, NPs bring limitations, partly because they can limit the analytical techniques used for their biological and in vivo validation. From that standpoint, designing innovative drug delivery systems requires advancements in the methods used for their testing and investigations. Considering the well-known ability of resazurin-based methods for rapid detection of bacterial metabolisms with very high sensitivity, in this work we report a novel optimization for tracking bacterial growth kinetics in the presence of NPs with specific characteristics, such as specific optical properties.

RESULTS

Arginine-functionalized gold composite (HAp/Au/arginine) NPs, used as the NP model for validation of the method, possess plasmonic properties and are characterized by intensive absorption in the UV/vis region with a surface plasmon resonance maximum at 540 nm. Due to the specific optical properties, the NP absorption intensively interferes with the light absorption measured during the evaluation of bacterial growth (optical density; OD600). The results confirm substantial nonspecific interference by NPs in the signal detected during a regular turbidity study used for tracking bacterial growth. Instead, during application of a resazurin-based method (Presto Blue), when a combination of absorption and fluorescence detection is applied, a substantial increase in the signal-to-noise ratio is obtained that leads to the improvement of the accuracy of the measurements as verified in three bacterial strains tested with different growth rates (E. coli, P. aeruginosa, and S. aureus).

CONCLUSIONS

Here, we described a novel procedure that enables the kinetics of bacterial growth in the presence of NPs to be followed with high time resolution, high sensitivity, and without sampling during the kinetic study. We showed the applicability of the Presto Blue method for the case of HAp/Au/arginine NPs, which can be extended to various types of metallic NPs with similar characteristics. The method is a very easy, economical, and reliable option for testing NPs designed as novel antimicrobials.

Effects and bioaccumulation of gold nanoparticles in the gilthead seabream (Sparus aurata) - Single and combined exposures with gemfibrozil

Gold nanoparticles (AuNPs) are found in a wide range of applications and therefore expected to present increasing levels in the environment. There is however limited knowledge concerning the potential toxicity of AuNPs as well as their combined effects with other pollutants. Hence, the present study aimed to investigate the effects of AuNPs alone and combined with the pharmaceutical gemfibrozil (GEM) on different biological responses (behaviour, neurotransmission, biotransformation and oxidative stress) in one of the most consumed fish in southern Europe, the seabream Sparus aurata. Fish were exposed for 96 h to waterborne 40 nm AuNPs with two coatings - citrate and polyvinylpyrrolidone (PVP), alone or combined with GEM. Antioxidant defences were induced in liver and gills upon both AuNPs exposure. Decreased swimming performance (1600 μg.L^-1) and oxidative damage in gills (4 and 80 μg.L^-1) were observed following exposure to polyvinylpyrrolidone coated gold nanoparticles (PVP-AuNPs). Generally, accumulation of gold in fish tissues and deleterious effects in S. aurata were higher for PVP-AuNPs than for cAuNPs exposures. Although AuNPs and GEM combined effects in gills were generally low, in liver, they were higher than the predicted. The accumulation and effects of AuNPs showed to be dependent on the size, coating, surface charge and aggregation/agglomeration state of nanoparticles. Additionally, it was tissue' specific and dependent on the presence of other contaminants. Although, gold intake by humans is expected to not exceed the estimated tolerable daily intake, it is highly recommended to keep it on track due to the increasing use of AuNPs.

Influences of simulated gastrointestinal environment on physicochemical properties of gold nanoparticles and their implications on intestinal epithelial permeability

Gold nanoparticles (Au NPs) hold great promise in food, industrial and biomedical applications due to their unique physicochemical properties. However, influences of the gastrointestinal tract (GIT), a likely route for Au NPs administration, on the physicochemical properties of Au NPs has been rarely evaluated. Here, we investigated the influence of GIT fluids on the physicochemical properties of Au NPs (5, 50, and 100 nm) and their implications on intestinal epithelial permeability in vitro. Au NPs aggregated in fasted gastric fluids and generated hydroxyl radicals in the presence of H₂O₂. Cell studies showed that GIT fluids incubation of Au NPs affected the cellular uptake of Au NPs but did not induce cytotoxicity or disturb the intestinal epithelial permeability.

Quantification of Loading and Laser-Assisted Release of RNA from Single Gold Nanoparticles

Novel RNA-based technologies provide an avenue of possibilities to control the regulation of gene expression in cells. To realize the full potential of small interfering RNA (siRNA)-based therapy, efficient delivery vehicles and novel strategies for triggering release from carrier vehicles have to be developed. Gold nanoparticles (AuNPs) with sizes of ∼50-150 nm have the ability to accumulate in tumor tissue and can be transported across the membrane by endocytosis. Therefore, a laser-controlled oligonucleotide release from such particles is of particular interest. Here, we quantify the loading of specifically attached microRNA oligonucleotides (miRNA) onto single gold nanoparticles with diameters of 80, 100, 150, and 200 nm. We show that AuNPs have a curvature-dependent density of miRNA loading: the higher the curvature, the higher the loading density. Moreover, we demonstrate how one sensing strand of an RNA duplex can be dehybridized and hence released from the AuNP by heating the AuNP by irradiation with a near-infrared (NIR) laser. Laser-induced release is also demonstrated inside living cells. Together, these findings show that plasmonic nanoparticles with high curvatures are ideal carriers of oligonucleotides into cells, and their cargo can be released in a controlled manner by a thermoplasmonic mechanism. Importantly, this remotely controlled release strategy can be applied to any cargo attached to a plasmonic nanocarrier, on either the single particle or ensemble level.

Acute exposure to gold induces fast changes in social behavior and oxidative stress of zebrafish (Danio rerio)

Gold is a noble metal having a long history of human usage and a variety of applications. The present paper was designed in order to see the changes on social and swimming behavior of zebrafish caused by acute gold exposure to high concentrations dissolved in aquatic medium from a standard solution with the highest purity. Some main oxidative stress markers were determined such as: superoxide dismutase (SOD), catalase (CAT), malondialdehyde (MDA) and glutathione peroxidase (GPx). We also focused our attention on the bioaccumulation capacity of gold in exposed zebrafish and its competition with essential elements for the body: sodium (Na), potassium (K), calcium (Ca), magnesium (Mg), iron (Fe), zinc (Zn) and copper (Cu). They were studied the effects of the follow gold concentrations dissolved in experimental aquariums: 1 mg L^-1 (Au 1 mg/L), 2 mg L^-1 (Au 2 mg/L), 4 mg L^-1 (Au 4 mg/L) and 8 mg L^-1 (Au 8 mg/L). Our data showed that each group treated with gold had a higher concentration compared with the others suggesting that it can be absorbed into the zebrafish body from environment and may be accumulated. The results obtained in the oxidative stress parameters demonstrated that it can produce changes as a response to its toxicological effects.

Effects of quercetin and arginine on the nephrotoxicity and lipid peroxidation induced by gold nanoparticles in vivo

INTRODUCTION

This study aimed to evaluate the nephrotoxicity caused by gold nanoparticles (GNPs) and investigate the potential roles of quercetin (Qur) and arginine (Arg) in mitigating the inflammatory kidney damage and dysfunction and inhibiting the toxicity induced by GNPs in rats.

METHODS

Kidney function was assessed using various serum biomarkers, including blood urea nitrogen (BUN), uric acid (URIC), and creatinine (CR), while toxicity was evaluated by measuring the biomarkers glutathione (GSH) and malondialdehyde (MDA) in kidney tissues.

RESULTS

Administration of GNPs to the rats severely affected the serum kidney biomarkers, as confirmed by the notable increases in BUN, URIC, and CR. Substantial changes in the levels of the biomarkers MDA and GSH in the kidney tissues were also observed, with a reduced level of GSH and elevated MDA activity. The administration of Qur or Arg exerted a protective effect against GNP-induced inflammatory kidney damage and toxicity, but with different responses according to their evaluated normalized values.

CONCLUSION

This study demonstrates the beneficial effects of supplementation with Qur or Arg during the treatment with GNPs, potentially providing a powerful tool for cancer therapy.

Toxic Effects of Size-tunable Gold Nanoparticles on Caenorhabditis elegans Development and Gene Regulation

We utilized size-tunable gold nanoparticles (Au NPs) to investigate the toxicogenomic responses of the model organism Caenorhabditis elegans. We demonstrated that the nematode C. elegans can uptake Au NPs coated with or without 11-mercaptoundecanoic acid (MUA), and Au NPs are detectable in worm intestines using X-ray microscopy and confocal optical microscopy. After Au NP exposure, C. elegans neurons grew shorter axons, which may have been related to the impeded worm locomotion behavior detected. Furthermore, we determined that MUA to Au ratios of 0.5, 1 and 3 reduced the worm population by more than 50% within 72 hours. In addition, these MUA to Au ratios reduced the worm body size, thrashing frequency (worm mobility) and brood size. MTT assays were employed to analyze the viability of cultured C. elegans primary neurons exposed to MUA-Au NPs. Increasing the MUA to Au ratios increasingly reduced neuronal survival. To understand how developmental changes (after MUA-Au NP treatment) are related to changes in gene expression, we employed DNA microarray assays and identified changes in gene expression (e.g., clec-174 (involved in cellular defense), cut-3 and fil-1 (both involved in body morphogenesis), dpy-14 (expressed in embryonic neurons), and mtl-1 (functions in metal detoxification and homeostasis)).

Engineered nanoparticles interact with nutrients to intensify eutrophication in a wetland ecosystem experiment

Despite the rapid rise in diversity and quantities of engineered nanomaterials produced, the impacts of these emerging contaminants on the structure and function of ecosystems have received little attention from ecologists. Moreover, little is known about how manufactured nanomaterials may interact with nutrient pollution in altering ecosystem productivity, despite the recognition that eutrophication is the primary water quality issue in freshwater ecosystems worldwide. In this study, we asked two main questions: (1) To what extent do manufactured nanoparticles affect the biomass and productivity of primary producers in wetland ecosystems? (2) How are these impacts mediated by nutrient pollution? To address these questions, we examined the impacts of a citrate-coated gold nanoparticle (AuNPs) and of a commercial pesticide containing Cu(OH)₂ nanoparticles (CuNPs) on aquatic primary producers under both ambient and enriched nutrient conditions. Wetland mesocosms were exposed repeatedly with low concentrations of nanoparticles and nutrients over the course of a 9-month experiment in an effort to replicate realistic field exposure scenarios. In the absence of nutrient enrichment, there were no persistent effects of AuNPs or CuNPs on primary producers or ecosystem productivity. However, when combined with nutrient enrichment, both NPs intensified eutrophication. When either of these NPs were added in combination with nutrients, algal blooms persisted for >50 d longer than in the nutrient-only treatment. In the AuNP treatment, this shift from clear waters to turbid waters led to large declines in both macrophyte growth and rates of ecosystem gross primary productivity (average reduction of 52% ± 6% and 92% ± 5%, respectively) during the summer. Our results suggest that nutrient status greatly influences the ecosystem-scale impact of two emerging contaminants and that synthetic chemicals may be playing an under-appreciated role in the global trends of increasing eutrophication. We provide evidence here that chronic exposure to Au and Cu(OH)₂ nanoparticles at low concentrations can intensify eutrophication of wetlands and promote the occurrence of algal blooms.

Modulation of immune genes mRNA levels in mucosal tissues and DNA damage in red blood cells of Sparus aurata by gold nanoparticles

Gold nanoparticles (AuNP) effects on Sparus aurata were evaluated on skin, gills and intestine by assessing the expression of immune genes and in peripheral blood evaluating genetic damage. Fish were exposed to 0.5 and 50 μg/L AuNP for 96 h. Results showed that exposure to 50 μg/L AuNP induced an upregulation in the expression of innate immune genes in gills (c3, lys, il1β, tnfα, il6, il10 and tgfβ) and intestine (il1β, tnfα and il6). Furthermore, mRNA levels of hsp70 and hsp90 were increased in gills after exposure to 0.5 μg/L AuNP, when compared to 50 μg/L. Present data demonstrated the sensitivity of gills and intestines to AuNP exposure supporting their use in the study of fish responses to other nanoparticles. Genotoxic potential of AuNP was demonstrated by increased DNA strand breaks in red blood cells of fish exposed to AuNP, suggesting that AuNP represent a potential hazard to fish.

Gold nanoparticles: A plausible tool to combat neurological bacterial infections in humans

Management of bacterial infections of central nervous system is a major challenge for the scientists all over the world. Despite the development of various potential drugs, the issue of central nervous system infections persists in the society. The main constraint is the delivery of drugs across the blood brain barrier and only a few drugs after meeting the stringent criteria could cross the blood brain barrier. On the other hand, certain bacterial pathogens could easily enter the brain by using several factors and mechanisms by crossing the blood brain barriers. Interestingly, in the recent past, gold nanoparticles have shown immense potential to overcome the issues associated with the treatment of central nervous system infections, especially due to their inherent ability to cross the blood brain barrier. Initially, the present review summarized the recent updates on the pathogenesis and factors involved in neurological bacterial infections, including the mechanism used by bacterial pathogens to cross the blood brain barriers. Thereafter, the emphasis of the review was on providing current information on gold nanoparticles pertinent to their applicability for the treatment of neurological infections. After discussing the background of neurological bacterial infections, the characteristic features, antibacterial properties, mechanisms of antibacterial action and ability to cross the blood brain barrier of gold nanoparticles have been summarized. Some of the features of gold nanoparticles that make them an ideal candidate for brain delivery are biocompatibity, stability, ability to get synthesized in different sizes with facile methods, surface affinity towards various functional groups, spontaneous crossing of blood brain barrier without applying any external field and most importantly, easy non-invasive tracing by CT imaging. The current updates on the development of gold nanoparticles based therapeutic strategies for the prevention and treatment of central nervous system infections have been discussed in the present study. However, further investigation would be required to translate these preclinical outcomes into clinical applications. Nevertheless, we could safely state that the information gathered and discussed in the present review would benefit the scientists working in the field of neuro-nanotechnology.

Toxicological interactions induced by chronic exposure to gold nanoparticles and microplastics mixtures in Daphnia magna

The effects of emerging environmental contaminants on human and environmental health is of high concern, especially those potentially induced by mixtures. The main goal of the present study was to assess the chronic effects of mixtures of citrate stabilized ≈5 nm gold nanoparticles (AuNP) and 1-5μm microplastics (MP) on Daphnia magna. A 21-day bioassay was carried out. The effect criteria were parental mortality, somatic growth and several reproductive parameters. AuNP induced parental mortality, reduced the total offspring and caused immobile juveniles and aborted eggs. MP induced parental mortality, delayed the first brood release, decreased the number of broods released, the total offspring, and caused immobile juveniles. All the mixtures caused higher toxicity than AuNP and MP alone. Based on parental mortality, evidences of antagonism between AuNP and MP were observed at low concentrations of both mixture components, whereas evidences of synergism at high concentrations were found. Chronic (21-day) exposure of D. magna to AuNPs, MP, and their mixtures can impair development, reproduction, ultimately leading to death.

In vivo bio-distribution, clearance and toxicity assessment of biogenic silver and gold nanoparticles synthesized from Abutilon indicum in Wistar rats

This study reports the bio-distribution and clearance of Abutilon indicum silver and gold nanoparticles (AIAgNPs and AIAuNPs) in Wistar rats. Rats in different groups were orally administered with 5 and 10 mg/Kg BW of AIAgNPs and AIAuNPs (size 1-25 nm) for 28 days and few were maintained until 58 days of washout period. Serum biochemical parameters were not changed significantly at both doses of AIAuNPs and at lower concentration of AIAgNPs. But, with 10 mg/Kg BW of AIAgNPs rats showed elevated levels of AST, ALP and ALT on day 29, however, these levels were restored to normal after washout period. Liver oxidative stress markers were not altered with the treatment of AIAgNPs and AIAuNPs. ICP-OES analysis indicated bio-distribution of Ag and Au more in liver, kidney and spleen on day 29 and was found cleared on day 59. Histological analysis of nine vital organs indicated normal tissue architecture at both doses of AIAuNPs and lower dose of AIAgNPs. While the rats treated with higher dose of AIAgNPs showed mild liver sinusoid cell swelling on day 29, which also was recovered on day 59. Findings of this preclinical study indicate biocompatible nature of biogenic nanoparticles supporting their future biomedical applications.

Non-invasive detection of the early phase of kidney injury by photoacoustic/computed tomography imaging

The early diagnosis of kidney diseases, which can remarkably impair the quality of life and are costly, has encountered great difficulties. Therefore, the development of methods for early diagnosis has great clinical significance. In this study, we used an emerging technique of photoacoustic (PA) imaging, which has relatively high spatial resolution and good imaging depth. Two kinds of PA gold nanoparticle (GNP)-based bioprobes were developed based on their superior photo detectability, size controllability and biocompatibility. The kidney injury mouse model was developed by unilateral ureteral obstruction for 96 h and the release of obstruction model). Giving 3.5 and 5.5 nm bioprobes by tail vein injection, we found that the 5.5 nm probe could be detected in the bladder in the model group, but not in the control group. These results were confirmed by computed tomography imaging. Furthermore, the model group did not show changes in the blood biochemical indices (BUN and Scr) and histologic examination. The 5.5 nm GNPs were found to be the critical point for early diagnosis of kidney injury. This new method was faster and more sensitive and accurate for the detection of renal injury, compared with conventional methods, and can be used for the development of a PA GNP-based bioprobe for diagnosing renal injury.

Synergistic Toxicity Produced by Mixtures of Biocompatible Gold Nanoparticles and Widely Used Surfactants

Nanoparticle safety is usually determined using solutions of individual particles that are free of additives. However, the size-dependent properties of nanoparticles can be readily altered through interactions with other components in a mixture. In applications, nanoparticles are commonly combined with surfactants or other additives to increase dispersion or to enhance product performance. Surfactants might also influence the biological activity of nanoparticles; however, little is known about such effects. We investigated the influence of surfactants on nanoparticle biocompatibility by studying mixtures of ligand-stabilized gold nanoparticles and Polysorbate 20 in embryonic zebrafish. These mixtures produced synergistic toxicity at concentrations where the individual components were benign. We examined the structural basis for this synergy using solution-phase analytical techniques. Spectroscopic and X-ray scattering studies suggest that the Polysorbate 20 does not affect the nanoparticle core structure. DOSY NMR showed that the hydrodynamic size of the nanoparticles increased, suggesting that Polysorbate 20 assembles on the nanoparticle surfaces. Mass spectrometry showed that these assemblies have both increased uptake and increased toxicity in zebrafish, as compared to the gold nanoparticles alone. We probed the generality of this synergy by performing toxicity assays with two other common surfactants, Polysorbate 80 and sodium dodecyl sulfate. These surfactants also caused synergistic toxicity, although the extent and time frame of the response depends upon the surfactant structure. These results demonstrate a need for additional, foundational studies to understand the effects of surfactants on nanoparticle biocompatibility and challenge traditional models of nanoparticle safety where the matrix is assumed to have only additive effects on nanoparticle toxicity.