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The following investigation was carried out to determine the effects of Selenium nanoparticles (Se NPs) on the growth rates, nutrient digestibility, and hematology of Cirrhinus mrigala fingerlings fed sunflower meal as basal diet. The experiment included seven test diets with varying Se levels (0, 0.5, 1, 1.5, 2, 2.5, and 3 mg/kg) based on Se NPs supplementation. Chromic oxide, an inert maker, was also added. Fingerlings were fed at a rate of 5% of their body weight. The test meal of 1 mg/kg Se NPs resulted in the highest weight gain (12.31 g) and the lowest feed conversion ratio (1.58). Best hematological indices (RBCs 2.84 10 6 mm -3 , WBCs 7.79 10 3 mm -3 , PLT 66, Hb 8.5 g/100 ml, PCV 25% and MCV 190 fl) and maximum nutrient absorption (crude protein 72%, ether extract 73% and gross energy 67%) were also observed in the case of 1 mg/kg supplementation of Se NPs. Hematology studies indicated that when fish were fed 0.5 mg/kg Se NPs, their levels began to rise. Maximum results were achieved with feed containing 1 mg/kg of Se NPs, but when the concentration increased above 1 mg/kg, the values began to decline. Instead, nutrient digestibility began to increase when the concentration of Se NPs increased to 1 mg/kg and abruptly started to decline with a further increase in Se NPs. The results demonstrated that a sunflower meal-based diet supplemented with Se NPs (1 mg/kg) increased the growth performance, nutritional digestibility, and hematology of C. mrigala fingerlings., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier GmbH. All rights reserved.)

This article reports the systematic photoluminescence study of the various contents of gold nanocomposites in polyvinyl alcohol (PVA) films. The variations in the gold content in PVA film were 0.2, 0.5, 1.0, and 1.5 wt%. All the samples were excited at two selected wavelengths; those are at 400 nm and 532 nm. On exciting the gold-PVA nanocomposite films at 400 nm the photoluminescence was observed in the region of 430-500 nm in comparison to pure PVA films that show an emission at 400 nm. However, on exciting the gold-PVA nanocomposites at 532 nm, the emission was observed at 560-650 nm with a long tail till 700 nm that is unlike the pure PVA films that do not show any emission peak in this region. This suggests that emission between 430 and 500 nm regions is due to the coordination of PVA with gold nanoparticles because PVA has an emission at 400 nm. However, the emission peak between 560 and 650 nm is entirely due to the gold nanocomposite particle. The peak also shows a smaller red-shift that is usually with the increasing nanoparticles size with the increasing content in the PVA films. The formation of gold nanoparticles was justified by X-ray diffraction (XRD) analysis which is further supported by X-ray photoelectron spectroscopy (XPS) analysis., (© 2023 John Wiley & Sons Ltd.)

Zinc oxide nanoparticles (ZnONPs) and melatonin (MT) have been known to regulate heavy metal toxicities in plants in some studies, the effect of their combined use on cadmium (Cd) uptake by wheat (Triticum aestivum L.) and underlying mechanisms is largely unknown. Thus, plant growth, uptake and translocation of Cd mediated by soil applied ZnONPs and foliar applied MT were investigated in wheat grown in Cd polluted soil under ambient conditions. The results depicted that ZnONPs stimulated the growth, chlorophyll contents, and yield of wheat in a dose additive way and this effect was further increased with foliar application of MT. 100 mg/kg of ZnONPs alone enhanced the grain yield by 60.5 % and this increase was about 177.5 % under combined ZnONPs and 100 μM MT treatment. ZnONPs treatments decreased Cd concentration whereas increased zinc (Zn) concentrations in shoots, roots, husks and grains and the effect was further increased with exogenous MT combined with NPs in a dose-additive way. 50 and 100 mg/kg ZnONPs treatments alone decreased grain Cd by 6.5 %, and 20 % and increased the Zn concentration by 20.1 % and 24 % than control. 100 mg/kg ZnONPs +100 μM MT treatment decreased the grain Cd by 63.5 % and increased grain Zn by 51 % than control treatment. Total Cd uptake (tissues biomass × Cd concentration in respective tissues) in shoots, roots, husks and grains increased with ZnONPs alone or combined with MT than control whereas soil post-harvest bioavailable Cd concentration decreased with treatments than control. The Cd reduction in grains was due to increase in biomass and Zn concentration thereby decreasing bioavailable Cd in soil and its accumulation in plants. This study suggested that combined use of ZnONPs and MT may provide new approaches for minimizing Cd and biofortification of Zn in edible parts of plants., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

The global biomass production from agricultural farmlands is facing severe constraints from abiotic stresses like soil salinization. Salinity-mediated stress triggered the overproduction of reactive oxygen species (ROS) that may result in oxidative burst in cell organelles and cause cell death in plants. ROS production is regulated by the redox homeostasis that helps in the readjustment of the cellular redox and energy state in plants. All these cellular redox related functions may play a decisive role in adaptation and acclimation to salinity stress in plants. The use of nanotechnology like nanoparticles (NPs) in plant physiology has become the new area of interest as they have potential to trigger the various enzymatic and non-enzymatic antioxidant capabilities of plants under varying salinity levels. Moreover, NPs application under salinity is also being favored due to their unique characteristics compared to traditional phytohormones, amino acids, nutrients, and organic osmolytes. Therefore, this article emphasized the core response of plants to acclimate the challenges of salt stress through auxiliary functions of ROS, antioxidant defense system and redox homeostasis. Furthermore, the role of different types of NPs mediated changes in biochemical, proteomic, and genetic expressions of plants under salt stress have been discussed. This article also discussed the potential limitations of NPs adoption in crop production especially under environmental stresses., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

The aim of the present study is to assess the effects of selenium nanoparticles on the growth, hematology and nutrients digestibility of Labeorohita fingerlings. Fingerlings were fed with seven isocaloric sunflower meal-based diet supplemented with different concentrations of nanoparticles naming T1 to T7 (0, 0.5, 1, 1.5, 2, 2.5, and 3 mg/kg), with 5% wet body weight while chromic oxide was used as an indigestible marker. After experimentation for 90 days T3 treated group (1mg/kg -1Se-nano level) showed the best result in hematological parameters (WBC's 7.97 ×103mm-3, RBC's 2.98 ×106 mm-3 and Platelet count 67), nutrient digestibility (crude protein: 74%, ether extract: 76%, gross energy: 70%) and growth performance (weight gain 13.24 g, weight gain% 198, feed conversion ratio 1.5, survival rate 100%) as compared to the other treatment groups. Specific growth rates were found significantly higher in T5 than in other groups. The present study indicated positive effect of 1 mg/kg Se-nanoparticles on growth advancement, hematological parameters, and nutrients digestibility of L. rohita fingerlings.

The main role of mitochondria is to generate the energy necessary for the cell to survive and adapt to different environmental stresses. Energy demand varies depending on the phenotype of the cell. To efficiently meet metabolic demands, mitochondria require a specific proton homeostasis and defined membrane structures to facilitate adenosine triphosphate production. This homeostatic environment is constantly challenged as mitochondria are a major target for damage after exposure to environmental contaminants. Here we report changes in mitochondrial structure profiles in different cell types using electron microscopy in response to particle stress exposure in three different representative lung cell types. Endpoint analyses include nanoparticle intracellular uptake; quantitation of mitochondrial size, shape, and ultrastructure; and confirmation of autophagosome formation. Results show that low-dose aluminum nanoparticles exposure (1 ppm; 1 µg/mL; 1.6 × 1 0 -7  µg/cell)) to primary and asthma cells incurred significant mitochondrial deformation and increases in mitophagy, while cancer cells exhibited only slight changes in mitochondrial morphology and an increase in lipid body formation. These results show low-dose aluminum nanoparticle exposure induces subtle changes in the mitochondria of specific lung cells that can be quantified with microscopy techniques. Furthermore, within the lung, cell type by the nature of origin (i.e. primary vs. cancer vs. asthma) dictates mitochondrial morphology, metabolic health, and the metabolic stress response of the cell.

Heteroaggregation behavior of gold nanospheres (AuNS) in presence of pluronic acid (PA) modified single-walled carbon nanotubes (PA-SWNTs) was systematically studied for a wide range of mono- and divalent (NaCl and CaCl(2)) electrolyte conditions. Homoaggregation rates of AuNS were also determined to delineate heteroaggregation mechanisms. Time resolved dynamic light scattering (DLS) was employed to monitor aggregation. The homoaggregation of AuNS showed classical Derjaguin-Landau-Verwey-Overbeek (DLVO) type behavior with defined reaction limited (RLCA) and diffusion limited (DLCA) aggregation regimes. PA-SWNTs homoaggregation on the one hand showed no response with electrolyte increase. AuNS heteroaggregation rates on the other hand, showed regime dependent response. At low electrolyte or RLCA regime, AuNS heteroaggregation showed significantly slower rates, compared to its homoaggregation behavior; whereas enhanced heteroaggregation was observed for DLCA regime. The key mechanisms of heteroaggregation of AuNS are identified as obstruction to collision at RLCA regime and facilitating enhanced attachment at DLCA regime manifested by the presence of PA-SWNTs. Presence of Suwannee River humic acid (SRHA) showed aggregation enhancement for both homo- and hetero-systems, in presence of divalent Ca(2+) ions. Bridging between SRHA molecules is identified as the key mechanism for increased aggregation rate. The findings of this study are relevant particularly to coexistence of engineered nanomaterials. The strategy of using nonaggregating PA-SWNTs is a novel experimental strategy that can be adopted elsewhere to further the heteroaggregation studies for a wider set of particles and surface coatings.

Aim: The purpose of the current study was to determine whether copper nanoparticles (Cu-NPs) can induce the release of proinflammatory mediators that influence the restrictive characteristics of the blood-brain barrier., Material & Methods: Confluent rat brain microvessel endothelial cells (rBMECs) were treated with well-characterized Cu-NPs (40 or 60 nm). Cytotoxicity of the Cu-NPs was evaluated by cell proliferation assay (1.5-50 µg/ml). The extracellular concentrations of proinflammatory mediators (IL-1β, IL-2, TNF-α and prostaglandin E(2)) were evaluated by ELISA., Results: The exposure of Cu-NPs at low concentrations increases cellular proliferation of rBMECs, by contrast, high concentrations induce toxicity. Prostaglandin E(2) release was significantly increased (threefold; 8 h) for Cu-NPs (40 and 60 nm). The extracellular levels of both TNF-α and IL-1β were significantly elevated following exposure to Cu-NPs. The P-apparent ratio, as an indicator of increased permeability of rBMEC was approximately twofold for Cu-NPs (40 and 60 nm)., Conclusion: These data suggest that Cu-NPs can induce rBMEC, proliferation at low concentrations and/or induce blood-brain barrier toxicity and potential neurotoxicity at high concentrations.

Ever since the discovery of carbon nanotubes, there has been an increasing interest in technologies that rely upon these incredibly small particles for their unique properties. However, assessment of their biological consequences has been riddled with assay limitations. Here, we describe application of a 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium cell viability assay to study cytotoxicity of various carbon-based nanomaterials on cells and discuss some pitfalls of this method.

Metallic nanomaterials, including silver, gold, and iron oxide, are being utilized in an increasing number of fields and specialties. The use of nanosilver as an antimicrobial agent is becoming ever-more common, whereas gold and iron oxide nanomaterials are frequently utilized in the medical field due to their recognized "biocompatibility". Numerous reports have examined the general toxicity of these nanomaterials; however, little data exists on how the introduction of these nanomaterials, at nontoxic levels, affects normal cellular processes. In the present study the impact of low levels of 10 nm silver (Ag-NP), gold (Au-NP), and iron oxide nanoparticles (SPION) on epidermal growth factor (EGF) signal transduction within the human epithelial cell line, A-431, was investigated. Following a biocompatibility assessment, the nanoparticle-induced interference at four specific targets within the EGF signaling process was evaluated: (1) nanoparticle-EGF association, (2) Akt and Erk phosphorylation, (3) Akt activity, and (4) EGF-dependent gene regulation. For all tested nanoparticles, following cellular exposure, a disruption in the EGF signaling response transpired; however, the metallic composition determined the mechanism of alteration. In addition to inducing high quantities of ROS, Ag-NPs attenuated levels of Akt and Erk phosphorylation. Au-NPs were found to decrease EGF-dependent Akt and Erk phosphorylation as well as inhibit Akt activity. Lastly, SPIONs produced a strong alteration in EGF activated gene transcription, with targeted genes influencing cell proliferation, migration, and receptor expression. These results demonstrate that even at low doses, introduction of Ag-NPs, Au-NPs, and SPIONs impaired the A-431 cell line's response to EGF.

Recent advances in particle-forming chemistries used for developing nanotechnology has not only widened novel applications for nanoscale materials but also has provided significant concern regarding their biological effects. The present study investigates the inflammatory responses of RAW 264.7 mouse macrophages exposed to nanoparticles (NPs, 5 μg/ml) of varied sizes including silver (Ag), aluminum (Al), carbon black (CB), carbon-coated silver (CAg) and gold (Au). A significant increase in IL-6, reactive oxygen species (ROS) generation, nuclear translocation of nuclear factor-kappa B (NF-κB), induction of cyclooxygenase-2 (COX-2), and tumor necrosis factor-alpha (TNF-α) expression was observed in macrophages with maximum response found in cells exposed to Ag NPs followed by Al, CB and CAg. These pro-inflammatory effects of NPs were dependent on size and duration of exposure and comparable to those induced by lipopolysaccharide (LPS), a known inflammatory mediator. Au NPs, on the other hand, induced small but significant inflammatory responses in macrophages upon prolonged exposure. These studies reveal that Ag NPs exhibit higher propensity in inducing inflammation, mediated by ROS and NF-κB signaling pathways and leading to the induction of COX-2, TNF-α and IL-6. However, no such prominent pro-inflammatory responses were observed with Au NPs, suggesting their bio-compatibility.

Near infrared (NIR) light, which spans wavelengths from ~700-1100 nm holds particular promise in bionanotechnology-enabled applications because both NIR light and nanoparticles (NPs) have the potential for remote activation leading to exquisite localization and targeting scenarios. In this study, aqueous solutions of carbon and metal-based NPs (carbon black, single-walled carbon nanotubes, silver nanoparticles and copper nanoparticles) were exposed to continuous NIR laser (λ = 1064 nm) irradiation at powers of 2.2W and 4.5W. The differential heating of bulk aqueous suspension of NPs with varying physicochemical properties revealed maximum temperatures of 67 °C with visible evidence of condensation and bubble formation. The basis of the NP heating is due to the strong intrinsic optical absorbance in the NIR spectral window and the transduction of this NIR photon energy into thermal energy. In this regard, UV-vis measurements can accurately predict NP heating kinetics prior to NIR irradiation. Further, a uniform thermodynamic heating model demonstrates close agreement with the experimental data for the low NIR-absorbing NPs. However, the uniform thermodynamic heating model used in this study does not accurately portray the energy release upon localized NP heating because of bubble formation for the highly absorbing NPs. Therefore, this study reveals the differential heating kinetics of NPs excited with NIR with implications in the development of novel NIR-NP-based systems., (© 2011 American Chemical Society)

Silver and titanium dioxide nanoparticles are known to induce oxidative stress in vitro and in vivo. Here we test if they impact development, mating success, and survivorship in Drosophila melanogaster, and if so, if these effects are reversible by antioxidants. Ingestion of nanotitanium dioxide during the larval stage of the life cycle showed no effects on development or survivorship, up to doses of 200 μg mL(-1). Conversely, ingestion of nanosilver had major dose, size, and coating-dependent effects on each of these aspects of life history. Each of these effects was partially or fully reversible by vitamin C. Larvae growing on nanosilver supplemented with vitamin C showed a greater than twofold increase in survivorship compared to flies reared on nanosilver alone, and a threefold increase in mating success. Vitamin C also rescued cuticular and pigmentation defects in nanosilver fed flies. Biochemical assays of superoxide dismutase and glutathione show these markers respond to nanotitanium dioxide and nanosilver induced oxidative stress, and this response is reduced by vitamin C. These results indicate that life history effects of nanosilver ingestion result from oxidative stress, and suggest antioxidants as a potential remediation for nanosilver toxicity. Conversely, the lack of nanotitanium dioxide life history toxicity shows that oxidative stress does not necessarily result in whole organism effects, and argues that nanoparticle toxicity needs to be examined at different levels of biological organization., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

We describe the use of transmission electron microscopy (TEM) for cellular ultrastructural examination of nanoparticle (NP)-exposed biomaterials. Preparation and imaging of electron-transparent thin cell sections with TEM provides excellent spatial resolution (approximately 1 nm), which is required to track these elusive materials. This protocol provides a step-by-step method for the mass-basis dosing of cultured cells with NPs, and the process of fixing, dehydrating, staining, resin embedding, ultramicrotome sectioning and subsequently visualizing NP uptake and translocation to specific intracellular locations with TEM. In order to avoid potential artifacts, some technical challenges are addressed. Based on our results, this procedure can be used to elucidate the intracellular fate of NPs, facilitating the development of biosensors and therapeutics, and provide a critical component for understanding NP toxicity. This protocol takes approximately 1 week.

The growth of the nanotechnology industry and subsequent proliferation of nanoparticle types present the need to rapidly assess nanoparticle toxicity. We present a novel, simple and cost-effective nebulizer-based method to deliver nanoparticles to the Drosophila melanogaster respiratory system, for the purpose of toxicity testing. FluoSpheres, silver, and CdSe/ZnS nanoparticles of different sizes were effectively aerosolized, showing the system is capable of functioning with a wide range of nanoparticle types and sizes. Red fluorescent CdSe/ZnS nanoparticles were successfully delivered to the fly respiratory system, as visualized by fluorescent microscopy. Silver coated and uncoated nanoparticles were delivered in a toxicity test, and induced Hsp70 expression in flies, confirming the utility of this model in toxicity testing. This is the first method developed capable of such delivery, provides the advantage of the Drosophila health model, and can serve as a link between tissue culture and more expensive mammalian models in a tiered toxicity testing strategy.

This study was undertaken to determine whether silver nanoparticles (Ag-45 nm NPs) induce selective and specific biological effects, such as induction of proliferation and nitric oxide (NO) production, and cytotoxicity in coronary endothelial cells (CECs), and regulation of vascular tone in isolated rat aortic rings. Physical characterization of Ag-45 nm NPs by transmission electron microscopy (TEM) demonstrated that nanoparticles ranging in size from 10 to 90 nm had biological effects on CECs. Increasing concentrations of Ag-45 nm NPs exerted a dual effect on cell proliferation whereby proliferation was inhibited at low concentrations of NPs and stimulated at high concentrations. The effects of high, but not low, concentrations of Ag-45 nm NPs were dependent on NO because the effects were partially blocked by N(G)-nitro-L-arginine methyl ester (L-NAME). We have also shown that high, but not low, concentrations of Ag-45 nm NPs induce NO-dependent proliferation through activation of endothelial nitric oxide synthase (eNOS) by phosphorylation of Serine 1177. Moreover, the antiproliferative and proliferative effects of Ag-45 nm NPs were concentration-dependent and inversely correlated with cellular toxicity. In isolated rat aortic rings, a low concentration of NPs induced vasoconstriction and a high concentration stimulated vasodilation. The physiologic effects induced by a low concentration of Ag-45 nm NPs inhibited acetylcholine- (ACh-) induced NO-mediated relaxation. Vasodilation induced by a high concentration of NPs was partially abolished by L-NAME pretreatment. When the endothelium was removed from the rings, all physiologic responses were blocked. These results clearly demonstrate that the NPs have selective and specific effects on the vascular endothelium in a concentration-dependent manner and suggest that opposite effects could be associated with NPs of different sizes.

The possibility that chronic exposure of nanoparticles may alter stress reaction and brain pathology following hyperthermia was examined in a rat model. Engineered nanoparticles from Ag or Cu (approximately equal to 50-60 nm) were administered (30 mg/kg, i.p.) once daily for 1 week in young male rats. On the 8th day these animals were subjected to 4 h heat stress at 38 degrees C in a BOD incubator. In these animals stress symptoms, blood-brain barrier (BBB) permeability, cognitive and motor functions and brain pathology were examined. Subjection of nanoparticle treated rats to heat stress showed exacerbation of stress symptoms i.e., hyperthermia, salivation and prostration and exhibited greater BBB disruption, brain edema formation, impairment of cognitive and motor functions and brain damage compared to normal animals. This enhanced brain pathology in heat stress was most marked in animals that received Ag nanoparticles compared to Cu treatment. Treatment with antioxidant compound H-290/51 either 30 min or 60 min after heat stress did not alter hyperthermia induce brain pathology in nanoparticle treated rats. Whereas, administration of nanowired-H-290/51 after 30 min or 60 min heat stress markedly attenuated BBB disruption, sensory motor function and brain pathology. These results suggest that chronic nanoparticles treatment exacerbate hyperthermia induced brain pathology that is significantly attenuated by nanowired but not normal H-290/51 compound. Taken together, our observations suggest that nano-wired drug delivery of H-290/51 is a promising approach to induce neuroprotection in hyperthermia induced brain pathology, not reported earlier.

Nanoparticles are small scale substances (<100 nm) used in biomedical applications, electronics, and energy production. Increased exposure to nanoparticles being produced in large-scale industry facilities elicits concerns for the toxicity of certain classes of nanoparticles. This study evaluated the effects of silver-25 nm (Ag-25) nanoparticles on gene expression in different regions of the mouse brain. Adult-male C57BL/6N mice were administered (i.p.) 100mg/kg, 500 mg/kg or 1,000 mg/kg Ag-25 and sacrificed after 24h. Regions from the brain were rapidly removed and dissected into caudate nucleus, frontal cortex and hippocampus. Total RNA was isolated from each of the three brain regions collected and real-time RT-PCR analysis was performed using Mouse Oxidative Stress and Antioxidant Defense Arrays. Array data revealed the expression of genes varied in the caudate nucleus, frontal cortex and hippocampus of mice when treated with Ag-25. The data suggest that Ag-25 nanoparticles may produce neurotoxicity by generating free radical-induced oxidative stress and by altering gene expression, producing apoptosis and neurotoxicity.

The rapid advancement of nanotechnology has created a vast array of engineered nanomaterials (ENMs) which have unique physical (size, shape, crystallinity, surface charge) and chemical (surface coating, elemental composition and solubility) attributes. These physicochemical properties of ENMs can produce chemical conditions to induce a pro-oxidant environment in the cells, causing an imbalanced cellular energy system dependent on redox potential and thereby leading to adverse biological consequences, ranging from the initiation of inflammatory pathways through to cell death. The present study was designed to evaluate size-dependent cellular interactions of known biologically active silver nanoparticles (NPs, Ag-15 nm, Ag-30 nm, and Ag-55 nm). Alveolar macrophages provide the first defense and were studied for their potential role in initiating oxidative stress. Cell exposure produced morphologically abnormal sizes and adherence characteristics with significant NP uptake at high doses after 24 h. Toxicity evaluations using mitochondrial and cell membrane viability along with reactive oxygen species (ROS) were performed. After 24 h of exposure, viability metrics significantly decreased with increasing dose (10-75 microg/mL) of Ag-15 nm and Ag-30 nm NPs. A more than 10-fold increase of ROS levels in cells exposed to 50 microg/mL Ag-15 nm suggests that the cytotoxicity of Ag-15 nm is likely to be mediated through oxidative stress. In addition, activation of the release of traditional inflammatory mediators were examined by measuring levels of cytokines/chemokines, including tumor necrosis factor (TNF-alpha), macrophage inhibitory protein (MIP-2), and interleukin-6 (IL-6), released into the culture media. After 24 h of exposure to Ag-15 nm nanoparticles, a significant inflammatory response was observed by the release of TNF-alpha, MIP-2, and IL-1beta. However, there was no detectable level of IL-6 upon exposure to silver nanoparticles. In summary, a size-dependent toxicity was produced by silver nanoparticles, and one predominant mechanism of toxicity was found to be largely mediated through oxidative stress.

In the present study, an ultrahigh-resolution system was applied as a simple and convenient technique to characterize the extent of metal nanoparticle agglomeration in solution and to visualize nanoparticle agglomeration, uptake, and surface interaction in three cell phenotypes under normal culture conditions. The experimental results demonstrated that silver (25, 80, 130 nm); aluminum (80 nm); and manganese (40 nm) particles and agglomerates were effectively internalized by rat liver cells (BRL 3A), rat alveolar macrophages (MACs), and rat neuroendocrine cells (PC-12). Individual and agglomerated nanoparticles were observed within the cells and agglomerates were observed on the cell surface membranes. The particles were initially dispersed in aqueous or physiological balanced salt solutions and agglomeration was observed using the Ultra Resolution Imaging (URI) system. Different methods, such as sonication and addition of surfactant (0.1% sodium dodecyl sulfate [SDS]) reduced agglomeration. Due to effects of SDS itself on cell viability, the surfactant could not be directly applied during cell exposure. Therefore, following addition of 0.1% SDS, the particles were washed twice with ultrapure water, which reduced agglomeration even further. Reducing the agglomeration of the nanoparticles is important for studying their uptake and in applications that benefit from individual nanoparticles such as diagnostics. In summary, this study demonstrates a simple technique to characterize the extent of nanoparticle agglomeration in solution and visualize nanoparticle (40 nm and larger) uptake and interaction with cells. Additionally, an example application of nanoparticle labeling onto the surface and neurite extensions of murine neuroblastoma cells (N2A) is presented as a potential imaging tool.

Finely divided carbon particles, including charcoal, lampblack, and diamond particles, have been used for ornamental and official tattoos since ancient times. With the recent development in nanoscience and nanotechnology, carbon-based nanomaterials (e.g., fullerenes, nanotubes, nanodiamonds) attract a great deal of interest. Owing to their low chemical reactivity and unique physical properties, nanodiamonds could be useful in a variety of biological applications such as carriers for drugs, genes, or proteins; novel imaging techniques; coatings for implantable materials; and biosensors and biomedical nanorobots. Therefore, it is essential to ascertain the possible hazards of nanodiamonds to humans and other biological systems. We have, for the first time, assessed the cytotoxicity of nanodiamonds ranging in size from 2 to 10 nm. Assays of cell viability such as mitochondrial function (MTT) and luminescent ATP production showed that nanodiamonds were not toxic to a variety of cell types. Furthermore, nanodiamonds did not produce significant reactive oxygen species. Cells can grow on nanodiamond-coated substrates without morphological changes compared to controls. These results suggest that nanodiamonds could be ideal for many biological applications in a diverse range of cell types.