Safe-by-design strategies for lowering the genotoxicity and pulmonary inflammation of multiwalled carbon nanotubes: Reduction of length and the introduction of COOH groups

Challenges and Opportunities: Nanomaterials in Epilepsy Diagnosis

Epilepsy is a common neurological disorder characterized by a significant rate of disability. Accurate early diagnosis and precise localization of the epileptogenic zone are essential for timely intervention, seizure prevention, and personalized treatment. However, over 30% of patients with epilepsy exhibit negative results on electroencephalography and magnetic resonance imaging (MRI), which can lead to misdiagnosis and subsequent delays in treatment. Consequently, enhancing diagnostic methodologies is imperative for effective epilepsy management. The integration of nanomaterials with biomedicine has led to the development of diagnostic tools for epilepsy. Key advancements include nanomaterial-enhanced neural electrodes, contrast agents, and biochemical sensors. Nanomaterials improve the quality of electrophysiological signals and broaden the detection range of electrodes. In imaging, functionalized magnetic nanoparticles enhance MRI sensitivity, facilitating localization of the epileptogenic zone. NIR-II nanoprobes enable tracking of seizure-related biomarkers with deep tissue penetration. Furthermore, nanomaterials enhance the sensitivity of biochemical sensors for detecting epilepsy biomarkers, which is crucial for early detection. These advancements significantly increase diagnostic sensitivity and specificity. However, challenges remain, particularly regarding biosafety, quality control, and the scalability of fabrication processes. Overcoming these obstacles is essential for successful clinical translation. Artificial-intelligence-based big data analytics can facilitate the development of diagnostic tools by screening nanomaterials with specific properties. This approach may help to address current limitations and improve both effectiveness and safety. This review explores the application of nanomaterials in the diagnosis and detection of epilepsy, with the objective of inspiring innovative ideas and strategies to enhance diagnostic effectiveness.

Intratracheal instillation for the testing of pulmonary toxicity in mice-Effects of instillation devices and feed type on inflammation

BACKGROUND

Inhalation exposure is the gold standard when assessing pulmonary toxicity. However, it typically requires substantial amounts of test material. Intratracheal instillation is an alternative administration technique, where the test substance is suspended in a liquid vehicle and deposited into the lung via the trachea. Instillation requires minimal test material, delivers an exact dose deep into the lung, and is less labor-intensive than inhalation exposures. However, one shortcoming is that the procedure may induce short-term inflammation. To minimize this, we tested different modifications of the technique to identify the potential for refinement.

METHODS

First, we tested whether previous findings of increased inflammation could be confirmed. Next, we tested whether instillation with a disposable 1 mL syringe with ball-tipped steel-needle (Disposable-syringe/steel-needle) induced less inflammation than the use of our standard set-up, a 250 μL reusable glass syringe with a disposable plastic catheter (Glass-syringe/plastic-catheter). Finally, we tested if access to pelleted and liquid feed prior to instillation affected inflammation. We evaluated inflammation by neutrophil numbers in bronchoalveolar fluid 24 h post-exposure.

RESULTS

Vehicle-instilled mice showed a small increase in neutrophil numbers compared to untreated mice. Neutrophil numbers were slightly elevated in the groups instilled with Disposable-syringe/steel-needle; an interaction with feed type indicated that the increase in neutrophils was more pronounced in combination with feed pellets compared to liquid feed. We found no difference between the feed types when using the Glass-syringe/plastic-catheter combination.

CONCLUSION

The Glass-syringe/plastic-catheter combination induced the least exposure-related inflammation, confirming this as a preferred instillation procedure.

Investigating the impact of Multiwalled Carbon Nanotubes exposure on enzymatic activities and histopathological variations in Swiss albino mice

Present study was conducted to evaluate the detrimental impacts of exposure of Multi-walled Carbon Nanotubes (MWCNT-NP) on enzymatic activities and tissue structures in Swiss albino mice. The experimental groups of mice received MWCNT-NP for specific time period (seven or fourteen days). Two distinct doses of the MWCNT-NP solution were given orally: 0.45 µg and 0.90 µg, and the distilled water was given to the control group. Serum samples were extracted at 7 and 14 days after the experiment by centrifuging whole blood for 15 min at 3,000 rpm. An enzyme-linked immunosorbent test (ELISA) was used to measure many enzyme assays, such as Angiotensin Converting Enzymes (ACE), Alanine Aminotransferase (ALT), Aspartate Aminotransferase (AST), and Nicotinamide Adenine Dinucleotide Phosphate (NADPH) oxidase enzyme. Hematoxylin and Eosin (H&E) staining of tissue samples was done along with a histopathological examination. During a 14-day exposure, ACE, NADPH Oxidase, ALT, and AST enzyme levels were significantly higher in the exposed groups (0.45 µg and 0.90 µg) than in the control group (p < 0.05). Male mice exposed to MWCNT-NP showed substantial histological damage in the relevant organs as well as elevated enzyme activity levels. Present study showed a comprehensive and practical assessment of the toxicity associated with MWCNT-NP of different geometries and functionalization.

Pulmonary toxicity and translocation of gallium phosphide nanowires to secondary organs following pulmonary exposure in mice

BACKGROUND

III-V semiconductor nanowires are envisioned as being integrated in optoelectronic devices in the near future. However, the perspective of mass production of these nanowires raises concern for human safety due to their asbestos- and carbon nanotube-like properties, including their high aspect ratio shape. Indeed, III-V nanowires have similar dimensions as Mitsui-7 multi-walled carbon nanotubes, which induce lung cancer by inhalation in rats. It is therefore urgent to investigate the toxicological effects following lung exposure to III-V nanowires prior to their use in industrial production, which entails risk of human exposure. Here, female C57BL/6J mice were exposed to 2, 6, and 18 µg (0.12, 0.35 and 1.1 mg/kg bw) of gallium phosphide (III-V) nanowires (99 nm diameter, 3.7 μm length) by intratracheal instillation and the toxicity was investigated 1, 3, 28 days and 3 months after exposure. Mitsui-7 multi-walled carbon nanotubes and carbon black Printex 90 nanoparticles were used as benchmark nanomaterials.

RESULTS

Gallium phosphide nanowires induced genotoxicity in bronchoalveolar lavage cells and acute inflammation with eosinophilia observable both in bronchoalveolar lavage and lung tissue (1 and 3 days post-exposure). The inflammatory response was comparable to the response following exposure to Mitsui-7 multi-walled carbon nanotubes at similar dose levels. The nanowires underwent partial dissolution in the lung resulting in thinner nanowires, with an estimated in vivo half-life of 3 months. Despite the partial dissolution, nanowires were detected in lung, liver, spleen, kidney, uterus and brain 3 months after exposure.

CONCLUSION

Pulmonary exposure to gallium phosphide nanowires caused similar toxicological effects as the multi-walled carbon nanotube Mitsui-7.

Genotoxicity in the absence of inflammation after tungsten inhalation in mice

Tungsten is used in several applications and human exposure may occur. To assess its pulmonary toxicity, we exposed male mice to nose-only inhalation of tungsten particles at 9, 23 or 132 mg/m³ (Low, Mid and High exposure) (45 min/day, 5 days/week for 2 weeks). Increased genotoxicity (assessed by comet assay) was seen in bronchoalveolar (BAL) fluid cells at Low and High exposure. We measured acellular ROS production, and cannot exclude that ROS contributed to the observed genotoxicity. We saw no effects on body weight gain, pulmonary inflammation, lactate dehydrogenase or protein in BAL fluid, pathology of liver or kidney, or on sperm counts. In conclusion, tungsten showed non-dose dependent genotoxicity in the absence of inflammation and therefore interpreted to be primary genotoxicity. Based on genotoxicity, a Lowest Observed Adverse Effect Concentration (LOAEC) could be set at 9 mg/m³. It was not possible to establish a No Adverse Effect Concentration (NOAEC).

The State of the Art and Challenges of In Vitro Methods for Human Hazard Assessment of Nanomaterials in the Context of Safe-by-Design

The Safe-by-Design (SbD) concept aims to facilitate the development of safer materials/products, safer production, and safer use and end-of-life by performing timely SbD interventions to reduce hazard, exposure, or both. Early hazard screening is a crucial first step in this process. In this review, for the first time, commonly used in vitro assays are evaluated for their suitability for SbD hazard testing of nanomaterials (NMs). The goal of SbD hazard testing is identifying hazard warnings in the early stages of innovation. For this purpose, assays should be simple, cost-effective, predictive, robust, and compatible. For several toxicological endpoints, there are indications that commonly used in vitro assays are able to predict hazard warnings. In addition to the evaluation of assays, this review provides insights into the effects of the choice of cell type, exposure and dispersion protocol, and the (in)accurate determination of dose delivered to cells on predictivity. Furthermore, compatibility of assays with challenging advanced materials and NMs released from nano-enabled products (NEPs) during the lifecycle is assessed, as these aspects are crucial for SbD hazard testing. To conclude, hazard screening of NMs is complex and joint efforts between innovators, scientists, and regulators are needed to further improve SbD hazard testing.

Comparison of biodistribution of cerium oxide nanoparticles after repeated oral administration by gavage or snack in Sprague Dawley rats

The rate of translocation of ingested nanoparticles (NPs) and how the uptake is affected by a food matrix are key aspects of health risk assessment. In this study, female Sprague Dawley rats (N = 4/group) received 0, 1.4, or 13 mg of cerium oxide (CeO₂ NM-212) NPs/rat/day by gavage or in a chocolate spread snack 5 days/week for 1 or 2 weeks followed by 2 weeks of recovery. A dose and time-dependent uptake in the liver and spleen of 0.1-0.3 and 0.004-0.005 parts per million (ng/mg) of the total administered dose was found, respectively. There was no statistically significant difference in cerium concentration in the liver or spleen after gavage compared to snack dosing. Microscopy revealed indications of necrotic changes in the liver and decreased cellularity in white pulp in the spleen. The snack provided precise administration and a more human-relevant exposure of NPs and could improve animal welfare as alternative to gavage.

Prospects of NIR fluorescent nanosensors for green detection of SARS-CoV-2

The pandemic of the novel coronavirus disease 2019 (COVID-19) is continuously causing hazards for the world. Effective detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) can relieve the impact, but various toxic chemicals are also released into the environment. Fluorescence sensors offer a facile analytical strategy. During fluorescence sensing, biological samples such as tissues and body fluids have autofluorescence, giving false-positive/negative results because of the interferences. Fluorescence near-infrared (NIR) nanosensors can be designed from low-toxic materials with insignificant background signals. Although this research is still in its infancy, further developments in this field have the potential for sustainable detection of SARS-CoV-2. Herein, we summarize the reported NIR fluorescent nanosensors with the potential to detect SARS-CoV-2. The green synthesis of NIR fluorescent nanomaterials, environmentally compatible sensing strategies, and possible methods to reduce the testing frequencies are discussed. Further optimization strategies for developing NIR fluorescent nanosensors to facilitate greener diagnostics of SARS-CoV-2 for pandemic control are proposed.

Surface functionalization and size modulate the formation of reactive oxygen species and genotoxic effects of cellulose nanofibrils

BACKGROUND

Cellulose nanofibrils (CNFs) have emerged as a sustainable and environmentally friendly option for a broad range of applications. The fibrous nature and high biopersistence of CNFs call for a thorough toxicity assessment, but it is presently unclear which physico-chemical properties could play a role in determining the potential toxic response to CNF. Here, we assessed whether surface composition and size could modulate the genotoxicity of CNFs in human bronchial epithelial BEAS-2B cells. We examined three size fractions (fine, medium and coarse) of four CNFs with different surface chemistry: unmodified (U-CNF) and functionalized with 2,2,6,6-tetramethyl-piperidin-1-oxyl (TEMPO) (T-CNF), carboxymethyl (C-CNF) and epoxypropyltrimethylammonium chloride (EPTMAC) (E-CNF). In addition, the source fibre was also evaluated as a non-nanosized material.

RESULTS

The presence of the surface charged groups in the functionalized CNF samples resulted in higher amounts of individual nanofibrils and less aggregation compared with the U-CNF. T-CNF was the most homogenous, in agreement with its high surface group density. However, the colloidal stability of all the CNF samples dropped when dispersed in cell culture medium, especially in the case of T-CNF. CNF was internalized by a minority of BEAS-2B cells. No remarkable cytotoxic effects were induced by any of the cellulosic materials. All cellulosic materials, except the medium fraction of U-CNF, induced a dose-dependent intracellular formation of reactive oxygen species (ROS). The fine fraction of E-CNF, which induced DNA damage (measured by the comet assay) and chromosome damage (measured by the micronucleus assay), and the coarse fraction of C-CNF, which produced chromosome damage, also showed the most effective induction of ROS in their respective size fractions.

CONCLUSIONS

Surface chemistry and size modulate the in vitro intracellular ROS formation and the induction of genotoxic effects by fibrillated celluloses. One cationic (fine E-CNF) and one anionic (coarse C-CNF) CNF showed primary genotoxic effects, possibly partly through ROS generation. However, the conclusions cannot be generalized to all types of CNFs, as the synthesis process and the dispersion method used for testing affect their physico-chemical properties and, hence, their toxic effects.