Metal oxide nanoparticles with low toxicity

An overview on dispersion procedures and testing methods for the ecotoxicity testing of nanomaterials in the marine environment

Considerable efforts have been devoted to develop or adapt existing guidelines and protocols, to obtain robust and reproducible results from (eco)toxicological assays on engineered nanomaterials (NMs). However, while many studies investigated adverse effects of NMs on freshwater species, less attention was posed to the marine environment, a major sink for these contaminants. This review discusses the procedures used to assess the ecotoxicity of NMs in the marine environment, focusing on the use of protocols and methods for preparing NMs dispersions and on the NMs physicochemical characterization in exposure media. To this purpose, a critical analysis of the literature since 2010 was carried out, based on the publication of the first NMs dispersion protocols. Among the 89 selected studies, only <5 % followed a standardized dispersion protocol combined with NMs characterization in ecotoxicological media, while more than half used a non-standardized dispersion method but performed NMs characterization. In the remaining studies, only partial or no information on dispersion procedures or on physicochemical characterization was provided. This literature review also highlighted that metal oxides NMs were the most studied (42 %), but with an increasing interest in last years towards nanoplastics (14 %) and multicomponent nanomaterials (MCNMs, 7 %), in line with the growing attention on these emerging contaminants. For all these NMs, primary producers as algae and bacteria were the most studied groups of marine species, in addition to mollusca, while organisms at higher trophic levels were less represented, likely due to challenges in evaluating adverse effects on more complex organisms. Thus, despite the wide use of NMs in different applications, standard dispersion protocols are not often used for ecotoxicity testing with marine species. However, the efforts to characterize NMs in ecotoxicological media recognize the importance of following conditions that are as standardized as possible to support the ecological hazard assessment of NMs.

Ligand free FeSn2 alloy nanoparticles for safe T2-weighted MR imaging of in vivo lung tumors

Biosafety is a critical issue for the successful translocation of nanomaterial-based therapeutic/diagnostic agents from bench to bedside. For instance, after the withdrawal of clinically approved magnetic resonance (MR) imaging contrast agents (CAs) due to their biosafety issues, there is a massive demand for alternative, efficient, and biocompatible MR contrast agents for future MRI clinical applications. To this end, here we successfully demonstrate the in vivo MR contrast abilities and biocompatibilities of ligand-free FeSn₂ alloy NPs for tracking in vivo lung tumors. In vitro and in vivo results reveal the FeSn₂ alloy NPs acting as appreciable T₂ weighted MR contrast agents to locate tumors. The construction of iron (Fe) on biocompatible tin (Sn) greatly facilitates the reduction of the intrinsic toxicities of Fe in vivo resulting in no significant abnormalities in liver and kidney functions. Therefore, we envision that constructing ligand-free alloy NPs will be a promising candidate for tracking in vivo tumors in future clinical applications.

A Polytetrafluoroethylene (PTFE) and Nano-Al2O3 Based Composite Coating with a Bacteriostatic Effect against E. coli and Low Cytotoxicity

The problem of bacterial contamination through surfaces is important for the food industry. In this regard, there is a growing interest in new coatings based on nanoparticles that can provide a long-term antibacterial effect. Aluminum oxide nanoparticles are a good candidate for such coatings due to their availability and good biocompatibility. In this study, a coating containing aluminum oxide nanoparticles was produced using polytetrafluoroethylene as a polymer matrix-a polymer that exhibits excellent mechanical and physicochemical properties and it is not toxic. The obtained coatings based on "liquid Teflon" containing various concentrations of nanoparticles (0.001-0.1 wt%) prevented the bacterial growth, and they did not exhibit a cytotoxicity on animal cells in vitro. Such coatings are designed not only to provide an antibacterial surface effect, but also to eliminate micro damages on surfaces that inevitably occur in the process of food production.

Photocatalytic Detoxification of Some Insecticides in Aqueous Media Using TiO2 Nanocatalyst

The present study was performed to fabricate a titanium dioxide (TiO₂) nanocatalyst with proper characteristics for the removal of some insecticides (dimethoate and methomyl) from aqueous media. A TiO₂ catalyst of regular (TiO₂-commercial-/H₂O₂/UV) or nano (TiO₂-synthesized-/H₂O₂/UV) size was employed as an advanced oxidation process by combining it with H₂O₂ under light. Moreover, the total detoxification of insecticides after treatment with the most effective system (TiO₂(s)/H₂O₂/UV) was also investigated through exploring the biochemical alterations and histopathological changes in the liver and kidneys of the treated rats. Interestingly, the present study reported that degradation rates of the examined insecticides were faster using the TiO₂ catalyst of nano size. Complete degradation of the tested insecticides (100%) was achieved under the TiO₂(s)/H₂O₂/UV system after 320 min of irradiation. The half-life values of the tested insecticides under H₂O₂/TiO₂(c)/UV were 43.86 and 36.28 for dimethoate and methomyl, respectively, whereas under the H₂O₂/TiO₂(c)/UV system, the half-life values were 27.72 and 19.52 min for dimethoate and methomyl, respectively. On the other hand, no significant changes were observed in the biochemical and histopathological parameters of rats administrated with water treated with TiO₂(s)/H₂O₂/UV compared to the control, indicating low toxicity of the TiO₂ nanocatalyst-. Altogether, the advanced oxidation processes using TiO₂ nanocatalyst can be considered as a promising and effective remediation technology for the complete detoxification of methomyl and dimethoate in water. However, further future research is needed to identify the possible breakdown products and to verify the safety of the used nanomaterials.

Differential response of immobile (pneumocytes) and mobile (monocytes) barriers against 2 types of metal oxide nanoparticles

BACKGROUND

Inhaled nanoparticles (NPs) challenges mobile and immobile barriers in the respiratory tract, which can be represented by type II pneumocytes (immobile) and monocytes (mobile) but what is more important for biological effects, the cell linage, or the type of nanoparticle? Here, we addressed these questions and we demonstrated that the type of NPs exerts a higher influence on biological effects, but cell linages also respond differently against similar type of NPs.

DESIGN

Type II pneumocytes and monocytes were exposed to tin dioxide (SnO₂) NPs and titanium dioxide (TiO₂) NPs (1, 10 and 50 μg/cm²) for 24 h and cell viability, ultrastructure, cell granularity, molecular spectra of lipids, proteins and nucleic acids and cytoskeleton architecture were evaluated.

RESULTS

SnO₂ NPs and TiO₂ NPs are metal oxides with similar physicochemical properties. However, in the absence of cytotoxicity, SnO₂ NPs uptake was low in monocytes and higher in type II pneumocytes, while TiO₂ NPs were highly internalized by both types of cells. Monocytes exposed to both types of NPs displayed higher number of alterations in the molecular patterns of proteins and nuclei acids analyzed by Fourier-transform infrared spectroscopy (FTIR) than type II pneumocytes. In addition, cells exposed to TiO₂ NPs showed more displacements in FTIR spectra of biomolecules than cells exposed to SnO₂ NPs. Regarding cell architecture, microtubules were stable in type II pneumocytes exposed to both types of NPs but actin filaments displayed a higher number of alterations in type II pneumocytes and monocytes exposed to SnO₂ NPs and TiO₂ NPs. NPs exposure induced the formation of large vacuoles only in monocytes, which were not seen in type II pneumocytes.

CONCLUSIONS

Most of the cellular effects are influenced by the NPs exposure rather than by the cell type. However, mobile, and immobile barriers in the respiratory tract displayed differential response against SnO₂ NPs and TiO₂ NPs in absence of cytotoxicity, in which monocytes were more susceptible than type II pneumocytes to NPs exposure.

Comparative Acute Toxicity and Oxidative Stress Responses in Three Aquatic Species Exposed to Stannic Oxide Nanoparticles and Stannic Chloride

We experimentally investigated the toxicity of stannic oxide nanoparticles (SnO₂ NPs) to three freshwater species including Scenedesmus obliquus, Daphnia magna, and Danio rerio. To evaluate effect, toxicological impacts were compared to that of stannic chloride (SnCl₄). Based on the actual concentration of Sn, SnO₂ NPs suspensions inhibited growth of S. obliquus in a dose-dependent manner, demonstrating a median effect concentration of 2.28 ± 0.53 mg/L. However, SnO₂ NP suspensions were found to exhibit limited acute toxicity in D. magna and D. rerio. Moreover, the toxicity of the SnO₂ NP suspension was lower than SnCl₄ for all three trophic aquatic organisms. Comparison of component-specific contribution to overall toxicity indicated that, in SnO₂ NP suspensions, particulate Sn more significantly contributed to toxicity than dissolved Sn-ions. Furthermore, we found that the toxic mechanism of the SnO₂ NP suspension involved the induction of oxidative stress by increasing intracellular ROS accumulation.

Progressive impairment of learning and memory in adult zebrafish treated by Al2O3 nanoparticles when in embryos

Al₂O₃ Nanoparticles (Al₂O₃-NPs) have been widely used because of their unique physical and chemical properties, and Al₂O₃-NPs can be released into the environment directly or indirectly. Our previous research found that 13 nm Al₂O₃-NPs can induce neural cell death and autophagy in primarily cultured neural cells in vitro. The aim of this study was to determine where Al₂O₃-NPs at 13 nm particle size can cause neural cells in vivo and assess related behavioural changes and involved potential mechanisms. Zebrafish from embryo to adult were selected as animal models. Learning and memory as functional indicators of neural cells in zebrafish were measured during the development from embryo to adult. Our results indicate that Al₂O₃-NPs treatment in zebrafish embryos stages can cause the accumulation of aluminium content in zebrafish brain tissue, leading to progressive impaired neurodevelopmental behaviours and latent learning and memory performance. Additionally, oxidative stress and disruption of dopaminergic transmission in zebrafish brain tissues are correlated with the dose-dependent and age-dependent accumulation of aluminium content. Moreover, the number of neural cells in the telencephalon tissue treated with Al₂O₃-NPs significantly declined, and the ultramicroscopic morphology indicated profound autophagy alternations. The results suggest that Al₂O₃-NPs has dose-dependent and time-dependent progressive damage on learning and memory performance in adult zebrafish when treated in embryos. This is the first study of the effects of Al₂O₃-NPs on learning and memory during the development of zebrafish from embryo to adult.

Kouzani A, Mosadegh B, Gharaie S. Blood Pressure Sensors: Materials, Fabrication Methods, Performance Evaluations and Future Perspectives

Advancements in materials science and fabrication techniques have contributed to the significant growing attention to a wide variety of sensors for digital healthcare. While the progress in this area is tremendously impressive, few wearable sensors with the capability of real-time blood pressure monitoring are approved for clinical use. One of the key obstacles in the further development of wearable sensors for medical applications is the lack of comprehensive technical evaluation of sensor materials against the expected clinical performance. Here, we present an extensive review and critical analysis of various materials applied in the design and fabrication of wearable sensors. In our unique transdisciplinary approach, we studied the fundamentals of blood pressure and examined its measuring modalities while focusing on their clinical use and sensing principles to identify material functionalities. Then, we carefully reviewed various categories of functional materials utilized in sensor building blocks allowing for comparative analysis of the performance of a wide range of materials throughout the sensor operational-life cycle. Not only this provides essential data to enhance the materials' properties and optimize their performance, but also, it highlights new perspectives and provides suggestions to develop the next generation pressure sensors for clinical use.

Anticandidal and In vitro Anti-Proliferative Activity of Sonochemically synthesized Indium Tin Oxide Nanoparticles

The present work demonstrates the synthesis, characterization and biological activities of different concentrations of tin doped indium oxide nanoparticles (Sn doped In2O3 NPs), i.e., (Sn/In = 5%, 10% and 15%). We have synthesized different size (38.11 nm, 18.46 nm and 10.21 nm) of Sn doped In2O3 NPs. by using an ultra-sonication process. The Sn doped In2O3 NPs were characterized by by x-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) which confirmed the successful doping of tin (Sn) with Indium oxide (In2O3). Anticandidal activity was performed by standard agar dilution method using Candida albicans for the study. The minimum inhibitory/fungicidal concentration (MIC/MFC) values recorded were, 8 & >8 mg/ml for pure In2O3 NPs, 4 & 8 mg/ml for 5%, 2 & 8 mg/ml for 10%, whereas 1 & >4 mg/ml for 15% Sn doped In2O3 NPs, respectively. The topographical alteration caused by Sn doped In2O3 NPs on Candida cells, was clearly observed by SEM examination. A significant enhancement in anticandidal activity was seen, when Candida cells were exposed to (Sn/In = 5%, 10% and 15%). Moreover, we have also evaluated the impact of Sn-In2O3 NPs on human colorectal carcinoma cells (HCT-116). The results demonstrated that Sn-In2O3 NPs (Sn/In = 5%, 10% and 15%), caused dose dependent decrease in the cancer cell viability as the low dosage (2.0 mg/mL) showed 62.11% cell viability, while 4.0, 8.0, 16.0, 32.0 mg/mL dosages showed 20.45%, 18.25%, 16.58%, and 15.58% cell viability. In addition, the treatment of Sn-In2O3 NPs also showed significant cellular and anatomical changes in cancer cells as examined by microscopes. We have also examined the impact of Sn-In2O3 NPs (5%, 10%, 15%) on normal cells (HEK-293) and the results demonstrate that Sn-In2O3 NPs did not reduce the cell viability of normal cells.

Chronic exposure of the freshwater alga Pseudokirchneriella subcapitata to five oxide nanoparticles: Hazard assessment and cytotoxicity mechanisms

The increasing use of nanoparticles (NPs) unavoidably enhances their unintended introduction into the aquatic systems, raising concerns about their nanosafety. This work aims to assess the toxicity of five oxide NPs (Al₂O₃, Mn₃O₄, In₂O₃, SiO₂ and SnO₂) using the freshwater alga Pseudokirchneriella subcapitata as a primary producer of ecological relevance. These NPs, in OECD medium, were poorly soluble and unstable (displayed low zeta potential values and presented the tendency to agglomerate). Using the algal growth inhibition assay and taking into account the respective 72 h-EC₅₀ values, it was possible to categorize the NPs as: toxic (Al₂O₃ and SnO₂); harmful (Mn₃O₄ and SiO₂) and non-toxic/non-classified (In₂O₃). The toxic effects were mainly due to the NPs, except for SnO₂ which toxicity can mainly be attributed to the Sn ions leached from the NPs. A mechanistic study was undertaken using different physiological endpoints (cell membrane integrity, metabolic activity, photosynthetic efficiency and intracellular ROS accumulation). It was observed that Al₂O_3, Mn₃O₄ and SiO₂ induced an algistatic effect (growth inhibition without loss of membrane integrity) most likely as a consequence of the cumulative effect of adverse outcomes: i) reduction of the photosynthetic efficiency of the photosystem II (Ф_PSII); ii) intracellular ROS accumulation and iii) loss of metabolic activity. SnO₂ NPs also provoked an algistatic effect probably as a consequence of the reduction of Ф_PSII since no modification of intracellular ROS levels and metabolic activity were observed. Altogether, the results here presented allowed to categorize the toxicity of the five NPs and shed light on the mechanisms behind NPs toxicity in the green alga P. subcapitata.

Titanium dioxide-based scanning powder can modulate cell activity of oral soft tissue - Insights from in vitro studies with L929 cells and periodontal fibroblasts

PURPOSE

To reveal the impact of titanium dioxide-based scanning powder for intraoral digital impression on the biological activity of oral fibroblasts.

METHODS

Murine L929 cells and human periodontal ligament (PDLF) and gingival fibroblasts (GF) were treated with ten-fold serial dilutions of scanning powder and the corresponding conditioned medium (filtrate of overnight incubation of powder in medium) starting with 30mg/ml. Bicinchoninic acid protein assay, formazan- and resazurin-based toxicity assays, live/dead and annexin V/propidium iodide (PI) staining and immunoassays for interleukin (IL)-6 and IL-8 were performed. Powder composition was analyzed using energy dispersive X-ray spectroscopy (EDS).

RESULTS

Formazan and resazurin conversion was lesser in L929 cells than PDLF and GF in the presence of scanning powder. Induction of cell death was caused by 30mg/ml of powder in L929 cells but not in PDLF and GF. No pronounced impact of the conditioned medium was seen in cytotoxicity assays or live/dead-, and annexin V/PI staining. In PDLF and GF IL-6 expression was increased by the powder, while there was a decrease in IL-8. Powder particles did not deplete protein from medium. EDS showed a heterogeneous mixture consisting predominantly of titanium dioxide.

CONCLUSIONS

Scanning powder decreased cell activity and induced cell death in L929 cells at high concentrations. Human oral fibroblasts showed an increase in IL-6 levels but more resistance to the cytotoxicity of the powder. Within the limitations of an in vitro study our results suggest that proper cleaning after scanning is of clinical relevance to avoid potential unwanted effects of the powder.

Ecotoxicity Assessment of Fe3O4 Magnetic Nanoparticle Exposure in Adult Zebrafish at an Environmental Pertinent Concentration by Behavioral and Biochemical Testing

Magnetic Nanoparticles (MNPs) are widely being investigated as novel promising multifunctional agents, specifically in the fields of development for theranostics, electronics, waste water treatment, cosmetics, and energy storage devices. Unique, superior, and indispensable properties of magnetization, heat transfer, and melting temperature make MNPs emerge in the field of therapeutics in future healthcare industries. However, MNPs ecotoxicity as well as behavioral toxicity is still unexplored. Ecotoxicity analysis may assist investigate MNPs uptake mechanism and its influence on bioavailability under a given set of environmental factors, which can be followed to investigate the biomagnification of MNPs in the environment and health risk possessed by them in an ecological food chain. In this study, we attempted to determine the behavioral changes in zebrafishes at low (1 ppm) or high (10 ppm) concentration levels of Fe₃O₄ MNPs. The synthesized Fe₃O₄ MNPs sized at 15 nm were characterized by the transmission electron microscope (TEM), the superconducting quantum interference device (SQUID) magnetometer, and the multiple behavior tests for novel tank, mirror biting, conspecific social interaction, shoaling, circadian rhythm, and short-term memory of zebrafish under MNPs chronic exposure were demonstrated. Low concentration MNP exposure did not trigger alteration for majority behavioral and biochemical tests in adult zebrafish. However, tight shoal groups were observed at a high concentration of MNPs exposure along with a modest reduction in fish exploratory behavior and a significant reduction in conspecific social interaction behavior. By using enzyme-linked immunosorbent assays (ELISA), we found a high dose of MNPs exposure significantly elevated cortisol, acetylcholine, and catalase levels while reducing serotonin, acetylcholine esterase, and dopamine levels in the brain. Our data demonstrates chronic MNPs exposure at an environmentally-relevant dose is relatively safe by supporting evidence from an array of behavioral and biochemical tests. This combinational approach using behavioral and biochemical tests would be helpful for understanding the MNPs association with anticipated colloids and particles effecting bioavailability and uptake into cells and organisms.

Evaluating the cytotoxicity of tin dioxide nanofibers

Tin dioxide nanofibers (SnDNFs) are small fibers that have many applications. Tin dioxide nanofibers can be used in cosmetics, solar cells, toxic gas release sensors, and air pollution control. To date there have been few studies on the cytotoxicity of SnDNFs. The goal of this research is to determine if electrospun SnDNFs are toxic in a lung cancer cell line (A549). Considering the nano-scale size of the fibers, they can easily be inhaled and enter the pulmonary system and cause toxic effects in the lung. Occupational exposure to SnDNFs has been linked to pulmonary disease, making the A549 cell line important in this study. Nanofiber toxicity can vary based upon the characteristics of the fibers. Smaller nanofibers have been shown to have more toxic effects than their larger counterparts. The synthesized SnDNFs were characterized using SEM, Raman spectroscopy, and powder X-ray diffractometer (PXRD). SEM images showed the fibers to be 200-300 nm in diameter. Raman spectroscopy and PXRD indicated that the fibers were in the rutile phase. After quantifying the SnDNFs, the fibers were introduced to A549 cells at concentrations ranging from 0.02-500 µg mL^-1 and incubated at 37°C. These cells were quantified with the MTT assay to measure cell proliferation (IC₅₀ = 0.02 mg mL^-1), while lactate dehydrogenase (LDH) leakage was used to determine cytotoxicity, and apoptosis assays to assess the mechanism of cell death. Increasing concentration of SnDNF generated a consequential decrease in cell proliferation and viability. The percent cytotoxicity of SnDNF was not significantly changed at the various concentrations and time frames. In order to gain additional insight about the mechanism of cytotoxicity of SnDNFs, genes with links to inflammation and apoptosis were evaluated and found to be over-expressed in treated cells. At the concentrations of SnDNF examined, SnDNF was mildly toxic to the A549 cells.

The toxicology of indium oxide

Indium oxide (In₂O₃) is a technologically important semiconductor essentially used, doped with tin oxide, to form indium tin oxide (ITO). It is poorly soluble in all so far tested physiologic media. After repeated inhalation, In₂O₃ particles accumulate in the lungs. Their mobilization can cause significant systemic exposure over long periods of time. An increasing number of cases of severe lung effects (characterized by pulmonary alveolar proteinosis, emphysema and/or interstitial fibrosis) in workers of the ITO industry warrants a review of the toxicological hazards also of In₂O₃. The database on acute and chronic toxicity/carcinogenicity/genotoxicity/reproductive toxicity as well skin/eye irritation and sensitization is very limited or even lacking. Short-term and subchronic inhalation studies in rats and mice revealed persistent alveolar proteinosis, inflammation and early indicators of fibrosis in the lungs down to concentrations of 1 mg/m³. Epidemiological and medical surveillance studies, serum/blood indium levels in workers as well as data on the exposure to airborne indium concentrations indicate a need for measures to reduce exposure at In₂O₃ workplaces.