Nano-safety Research: Examining the Associations among the Biological Effects of Nanoparticles and Their Physicochemical Properties and Kinetics

Nanoparticles in tumor microenvironment remodeling and cancer immunotherapy

Cancer immunotherapy and vaccine development have significantly improved the fight against cancers. Despite these advancements, challenges remain, particularly in the clinical delivery of immunomodulatory compounds. The tumor microenvironment (TME), comprising macrophages, fibroblasts, and immune cells, plays a crucial role in immune response modulation. Nanoparticles, engineered to reshape the TME, have shown promising results in enhancing immunotherapy by facilitating targeted delivery and immune modulation. These nanoparticles can suppress fibroblast activation, promote M1 macrophage polarization, aid dendritic cell maturation, and encourage T cell infiltration. Biomimetic nanoparticles further enhance immunotherapy by increasing the internalization of immunomodulatory agents in immune cells such as dendritic cells. Moreover, exosomes, whether naturally secreted by cells in the body or bioengineered, have been explored to regulate the TME and immune-related cells to affect cancer immunotherapy. Stimuli-responsive nanocarriers, activated by pH, redox, and light conditions, exhibit the potential to accelerate immunotherapy. The co-application of nanoparticles with immune checkpoint inhibitors is an emerging strategy to boost anti-tumor immunity. With their ability to induce long-term immunity, nanoarchitectures are promising structures in vaccine development. This review underscores the critical role of nanoparticles in overcoming current challenges and driving the advancement of cancer immunotherapy and TME modification.

Effect of spraying air freshener on particulate and volatile organic compounds in vehicles

People in these days spend approximately 6 % of their time in a means of transport. Air fresheners are frequently used in vehicles to mask odors; however, they can cause adverse health effects such as cardiovascular disease, systemic inflammation and autonomic dysfunction. This study aimed to identify the effects of air fresheners on the concentrations of particulate and volatile organic compounds (VOCs) in different vehicle cabins. Scanning mobility and optical particle sizers were used for the particle measurements. VOCs (e.g., BTEX and d-limonene) were collected using a Tenax TA. The products were sprayed for less than a minute. The study assessed three spray products (all trigger types), vehicle size (small, medium, and large), cabin temperature (10 °C, 20 °C, and 25 °C), and in-vehicle ventilation mode (all-off, recirculation, and external inflow modes). The particle concentration increased rapidly during the 1-min spraying of the products. The proportion of nanoparticles in the front seat (67.2 % ± 2.2 %) was 11.1 % ± 2.2 % lower than that in the rear seat (75.6 % ± 2.1 %). The spray product and vehicle size did not significantly affect the particle or VOC concentrations. With an increase in the temperature of the front seat, the proportion of nanoparticles increased by 25.3 % ± 3.2 %. Moreover, the maximum total VOC concentrations (front seat: 364.3 μg/m3; back seat: 241.3 μg/m3) were observed at 20 °C. Under in-vehicle ventilation, recirculation effectively reduced the overall particle concentration within the cabin; however, the generated VOCs circulated. The external inflow proved effective in cabin air purification by reducing the total VOC concentration to 56.0-57.2 % compared with other ventilation modes. These findings provide substantial insight into the persistence of particles and the dynamics of their dispersion, thereby enabling informed decision-making for particle-related risk management.

Silver nanoparticles suppress forskolin-induced syncytialization in BeWo cells

Opportunities for the exposure of pregnant women to engineered nanoparticles have been increasing with the expanding use of these materials. Therefore, there are concerns that nanoparticles could have adverse effects on the establishment and maintenance of pregnancy. The effects of nanoparticles on the mother and fetus have been evaluated from this perspective, but there is still little knowledge about the effects on placentation and function acquisition, which are essential for the successful establishment and maintenance of pregnancy. Formation of the syncytiotrophoblast is indispensable for the acquisition of placental function, and impairment of syncytialization inevitably affects pregnancy outcomes. Here, we assessed the effect of nanoparticles on placental formation by using forskolin-treated BeWo cells, a typical in vitro model of trophoblast syncytialization. Immunofluorescence staining analysis revealed that silver nanoparticles with a diameter of 10 nm (nAg10) (at 0.156 µg/mL) significantly decreased the proportion of syncytialized BeWo cells, but gold nanoparticles with a diameter of 10 nm did not. Consistently, only nAg10 (at 0.156 µg/mL) significantly suppressed forskolin-induced elevation of CGB and SDC1 mRNA expression levels and human chorionic gonadotropin β production in a dose-dependent manner; these molecules are all markers of syncytialization. Besides, nAg10 significantly decreased the expression of ERVFRD-1, which encodes proteins associated with cell fusion. Moreover, nAg10 tended to suppress the expression of sFlt-1 e15a, a placental angiogenesis marker. Collectively, our data suggest that nAg10 could suppress formation of the syncytiotrophoblast and that induce placental dysfunction and the following poor pregnancy outcomes.

Toxicokinetics of zinc oxide nanoparticles and food grade bulk-sized zinc oxide in rats after oral dosages

The increasing application of zinc oxide nanoparticles (ZnO NPs) in consumer products has raised concerns about the potential health risks in human. It is crucial to understand the toxicokinetic information of ZnO NPs, especially the differences between NPs and non-nano form material. This study investigated the toxicokinetic profile of ZnO NPs and food grade bulk-sized ZnO in rats after single or repeated oral dosages. For single oral administration of ZnO suspensions at 350 mg/kgbw, the Zn content in blood and tissues showed no elevation, the majority of ZnO particles were eliminated via feces within 48 h. For repeated oral exposure to ZnO suspensions at 350 mg/kgbw or ZnSO₄ solution at 700 mg/kgbw for 90 days, elevated Zn levels were observed in liver, kidney, and bone in all three treatment groups, the Zn level recovered to normal level in liver and kidney, but not in bone, after a recovery period. ZnO NPs and bulk-sized ZnO showed similarity in toxicokinetics in rats, regardless of exposure duration or gender. ZnO particles shared a similar biodistribution profile with ZnSO₄, and were likely to be absorbed mostly in ionic forms.

Guidance on risk assessment of nanomaterials to be applied in the food and feed chain: human and animal health

The EFSA has updated the Guidance on risk assessment of the application of nanoscience and nanotechnologies in the food and feed chain, human and animal health. It covers the application areas within EFSA's remit, including novel foods, food contact materials, food/feed additives and pesticides. The updated guidance, now Scientific Committee Guidance on nano risk assessment (SC Guidance on Nano-RA), has taken account of relevant scientific studies that provide insights to physico-chemical properties, exposure assessment and hazard characterisation of nanomaterials and areas of applicability. Together with the accompanying Guidance on Technical requirements for regulated food and feed product applications to establish the presence of small particles including nanoparticles (Guidance on Particle-TR), the SC Guidance on Nano-RA specifically elaborates on physico-chemical characterisation, key parameters that should be measured, methods and techniques that can be used for characterisation of nanomaterials and their determination in complex matrices. The SC Guidance on Nano-RA also details aspects relating to exposure assessment and hazard identification and characterisation. In particular, nanospecific considerations relating to in vitro/in vivo toxicological studies are discussed and a tiered framework for toxicological testing is outlined. Furthermore, in vitro degradation, toxicokinetics, genotoxicity, local and systemic toxicity as well as general issues relating to testing of nanomaterials are described. Depending on the initial tier results, additional studies may be needed to investigate reproductive and developmental toxicity, chronic toxicity and carcinogenicity, immunotoxicity and allergenicity, neurotoxicity, effects on gut microbiome and endocrine activity. The possible use of read-across to fill data gaps as well as the potential use of integrated testing strategies and the knowledge of modes or mechanisms of action are also discussed. The Guidance proposes approaches to risk characterisation and uncertainty analysis.

Increasing the Power of Polyphenols through Nanoencapsulation for Adjuvant Therapy against Cardiovascular Diseases

Polyphenols play a therapeutic role in vascular diseases, acting in inherent illness-associate conditions such as inflammation, diabetes, dyslipidemia, hypertension, and oxidative stress, as demonstrated by clinical trials and epidemiological surveys. The main polyphenol cardioprotective mechanisms rely on increased nitric oxide, decreased asymmetric dimethylarginine levels, upregulation of genes encoding antioxidant enzymes via the Nrf2-ARE pathway and anti-inflammatory action through the redox-sensitive transcription factor NF-κB and PPAR-γ receptor. However, poor polyphenol bioavailability and extensive metabolization restrict their applicability. Polyphenols carried by nanoparticles circumvent these limitations providing controlled release and better solubility, chemical protection, and target achievement. Nano-encapsulate polyphenols loaded in food grade polymers and lipids appear to be safe, gaining resistance in the enteric route for intestinal absorption, in which the mucoadhesiveness ensures their increased uptake, achieving high systemic levels in non-metabolized forms. Nano-capsules confer a gradual release to these compounds, as well as longer half-lives and cell and whole organism permanence, reinforcing their effectiveness, as demonstrated in pre-clinical trials, enabling their application as an adjuvant therapy against cardiovascular diseases. Polyphenol entrapment in nanoparticles should be encouraged in nutraceutical manufacturing for the fortification of foods and beverages. This study discusses pre-clinical trials evaluating how nano-encapsulate polyphenols following oral administration can aid in cardiovascular performance.

Factors affecting the biological response of Graphene

Nanotechnology has gained significant importance in different fields of medical, electronic, and environmental science. This technology is founded on the use of materials at the nanoscale scale (1-100 nanometers) for various purposes, particularly in the biomedical area, where its application is growing daily due to the need of materials with advanced properties. Over the past few years, there has been a growing use for graphene and its derivative composite materials. However, different physico-chemical properties influence its biological response; therefore, further studies to explain the interactions of these nanomaterials with biological systems are critical. This review presents the current advances in the applications of graphene in biomedicine with a focus on the physico-chemical characteristics of the graphene family and their influences on biological interactions.

Engineering Nanoparticles toward the Modulation of Emerging Cancer Immunotherapy

Cancer immunotherapy is a new therapeutic strategy to fight cancer by activating the patients' own immune system. At present, immunotherapy approaches such as cancer vaccines, immune checkpoint blockade (ICB), adoptive cell transfer (ACT), monoclonal antibodies (mAbs) therapy, and cytokines therapy have therapeutic potential in preclinical and clinical applications. However, the intrinsic limitations of conventional immunotherapy are difficulty of precise dosage control, insufficient enrichment in tumor tissues, partial immune response silencing or hyperactivity, and high cost. Engineering nanoparticles (NPs) have been emerging as a promising multifunctional platform to enhance conventional immunotherapy due to their intrinsic immunogenicity, convenient delivery function, controlled surface chemistry activity, multifunctional modifying potential, and intelligent targeting. This review presents the recent progress reflected by engineering NPs, including the diversified selection of functionalized NPs, the superiority of engineering NPs for enhancing conventional immunotherapy, and NP-mediated multiscale strategies for synergistic therapy consisting of compositions and their mechanism. Finally, the perspective on multifunctional NP-based cancer immunotherapy for boosting immunomodulation is discussed, which reveals the expanding landscape of engineering NPs in clinical translation.

Impact of zinc oxide nanoparticles on thioredoxin-interacting protein and asymmetric dimethylarginine as biochemical indicators of cardiovascular disorders in gamma-irradiated rats

Nanoparticle is a microscopic particle that has been existed in a wide range of biotechnological purposes. Zinc oxide nanoparticles (ZnO-NPs) have fewer environmental hazards and have shown positive impacts in the medical field. This work aimed to observe the effects of low and high doses of ZnO-NPs on heart injury induced by ionizing radiation (IR). Animals were irradiated by 8 Gy of gamma rays and ZnO-NPs (10 and 300 mg/Kg/day) were orally delivered to rats 1 hour after irradiation. Animals were dissected on 15th day postirradiation. Data showed that the oxidative damage resulted from radiation exposure, appeared by marked increments in the malondialdehyde (MDA) content and the level and protein expression of thioredoxin-interacting protein (TXNIP) with a noticeable decline in the level and expression of thioredoxin 1 (Trx-1) and thioredoxin reductase (TrxR), as well as glutathione (GSH) level and the activity of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx). Moreover, radiation-induced inflammation, manifested by a noticeable elevation in the level of tumor necrotic factor-alpha (TNF-α), interleukin-18 (IL-18), and C-reactive protein (CRP). Additionally, endothelial dysfunction marked with a high level of asymmetric dimethylarginine (ADMA), total nitrite/nitrate (NOx), intercellular adhesion molecule 1 (ICAM-1), homocysteine (Hcy), creatine kinase (CK-MB), cardiac troponin-I (cTn-I), and lactate dehydrogenase (LDH). In addition, a decrease of zinc (Zn) level in the cardiac tissue was recorded. ZnO-NPs treatment (10 mg/kg) mitigated the oxidative stress and inflammation effects on the cardiovascular tissue through the positive modulations in the studied parameters. In contrast, ZnO-NPs treatment (300 mg/kg) induced cardiovascular toxicity of normal rats and elevated the deleterious effects of radiation. In conclusion, ZnO-NPs at a low dose could mitigate the adverse effects on cardiovascular tissue induced by radiation during its applications, while the high dose showed morbidity and mortality in normal and irradiated rats.

Quantitative Flow Cytometric Evaluation of Oxidative Stress and Mitochondrial Impairment in RAW 264.7 Macrophages after Exposure to Pristine, Acid Functionalized, or Annealed Carbon Nanotubes

Conventional nanotoxicological assays are subjected to various interferences with nanoparticles and especially carbon nanotubes. A multiparametric flow cytometry (FCM) methodology was developed here as an alternative to quantify oxidative stress, mitochondrial impairment, and later cytotoxic and genotoxic events. The experiments were conducted on RAW264.7 macrophages, exposed for 90 min or 24 h-exposure with three types of multiwalled carbon nanotubes (MWCNTs): pristine (Nanocyl™ CNT), acid functionalized (CNTf), or annealed treatment (CNTa). An original combination of reactive oxygen species (ROS) probes allowed the simultaneous quantifications of broad-spectrum ROS, superoxide anion (O₂^•-), and hydroxyl radical (•OH). All MWCNTs types induced a slight increase of broad ROS levels regardless of earlier antioxidant catalase activity. CNTf strongly stimulated the O₂^•- production. The •OH production was downregulated for all MWCNTs due to their scavenging capacity. The latter was quantified in a cell-free system by electron paramagnetic resonance spectroscopy (EPR). Further FCM-based assessment revealed early biological damages with a mitochondrial membrane potential collapse, followed by late cytotoxicity with chromatin decondensation. The combined evaluation by FCM analysis and cell-free techniques led to a better understanding of the impacts of MWCNTs surface treatments on the oxidative stress and related biological response.

Nanoparticles for mucosal vaccine delivery

Mucosal surfaces represent important routes of entry into the human body for the majority of pathogens, and they constitute unique sites for targeted vaccine delivery. Nanoparticle-based drug delivery systems are emerging technologies for delivering and improving the efficacy of mucosal vaccines. Recent studies have provided new insights into formulation and delivery aspects of importance for the design of safe and efficacious mucosal subunit vaccines based on nanoparticles. These include novel nanomaterials, their physicochemical properties and formulation approaches, nanoparticle interaction with immune cells in the mucosa, and mucosal immunization and delivery strategies. Here, we present recent progress in the application of nanoparticle-based approaches for mucosal vaccine delivery and discuss future research challenges and opportunities in the field.

Ionic-liquid-based microextraction method for the determination of silver nanoparticles in consumer products

A simple method to determine hazardous silver nanoparticles (AgNPs) based on ionic liquid (IL) dispersive liquid-liquid microextraction and back-extraction is described. This approach involves AgNP stabilization using a cationic surfactant followed by extraction from the sample matrix by means of an IL as an extraction phase. Certain ILs have high affinity for metals, and preliminary experiments showed that those ILs consisting of imidazolium cation efficiently extracted AgNPs in the presence of a cationic surfactant and a chelating agent. Afterward, histamine was used as a dispersing agent to promote phase transfer of differently coated AgNPs from the IL in aqueous solution to be subsequently analyzed by UV-visible spectrometry. The analytical procedure allows AgNPs to be recovered from the sample matrix in an aqueous medium, the enrichment factor being up to 4, preserving both AgNP size and AgNP shape as demonstrated by transmission electron microscopy images and the localized surface plasmon resonance band characteristic of each AgNP. The present method exhibited a linear response for AgNPs in the range from 3 to 20 μg/mL, the limit of detection being 0.15 μg/mL. Method efficiency was assessed in spiked orange juice and face cream, yielding recoveries ranging from 75.7% to 96.6%. The method was evaluated in the presence of other nanointerferents (namely, gold nanoparticles). On the basis of diverse electrophoretic mobilities and surface plasmon resonance bands for metal nanoparticles, capillary electrophoresis was used to prove the lack of interaction of the target AgNPs with gold nanoparticles during the whole protocol; thus, interferents do not affect AgNP determination. As a consequence, the analytical approach described has great potential for the analysis of engineered nanosilver in consumer products. Graphical abstract Simple protocol for the determination of silver nanoparticles (AgNPs) based on dispersive liquid-liquid extraction with a specific short alkyl side chain ionic liquid and their quantitative detection with a UV-visible spectrometer. HMIM•PF₆ 1-hexyl-3-methylimidazolium hexafluorophosphate, NP nanoparticle, SPR surface plasmon resonance.

Toxicity of carbon-based nanomaterials: Reviewing recent reports in medical and biological systems

Application of nanomaterials in our daily life is increasing, day in day out and concerns have raised about their toxicity for human and other organisms. In this manner, carbon-based nanomaterials have been applied to different products due to their unique physicochemical, electrical, mechanical properties, and biological compatibility. But, there are several reports about the negative effects of these materials on biological systems and cellular compartments. This review article describes the various types of carbon-based nanomaterials and methods that use for determining these toxic effects that are reported recently in the papers. Then, extensively discussed the toxic effects of these materials on the human and other living organisms and also their toxicity routs including Neurotoxicity, Hepatotoxicity, Nephrotoxicity, Immunotoxicity, Cardiotoxicity, Genotoxicity and epigenetic toxicity, Dermatotoxicity, and Carcinogenicity.

Developmental neurotoxicity and immunotoxicity induced by graphene oxide in zebrafish embryos

Graphene oxide (GO) has emerged as the worldwide promising candidate for biomedical application, such as for drug delivery, bio-sensing and anti-cancer therapy. This study was focused on the zebrafish and RAW264.7 cell line as in vivo and in vitro models to assess the potential developmental neurotoxicity and immunotoxicity of GO. No obvious acute developmental toxicity was observed upon treatments with 0.01, 0.1, and 1 μg/mL GO for five consecutive days. However, decreased hatching rate, increased malformation rate, heart beat rate and hypoactivity of locomotor behavior were detected when exposed to 10 μg/mL GO. Also, RT-PCR analysis revealed that expressions of genes related to the nervous system were up-regulated. The potential risk of GO for developmental neurotoxicity may be ascribed to the high level of oxidative stress induced by high concentration of GO. Most importantly, the mRNA levels of immune response associated genes, such as interleukin-6 (IL-6), interleukin-8 (IL-8), tumor necrosis factor-α (TNFα), interferon-γ (IFN-γ) were significantly increased under environmental concentration exposure. The activation of pro-inflammatory immune response was also observed in macrophage cell line. Taken together, our results demonstrated that immunotoxicity is a sensitive indicator for assessment of bio-compatibility of GO.

Embedding cell monolayers to investigate nanoparticle-plasmalemma interactions at transmission electron microscopy

Transmission electron microscopy is the technique of choice to visualize the spatial relationships between nanoconstructs and cells and especially to monitor the uptake process of nanomaterials. It is therefore crucial that the cell surface be preserved in its integrity, to obtain reliable ultrastructural evidence: the plasmalemma represents the biological barrier the nanomaterials have to cross, and the mode of membrane-nanoconstruct interaction is responsible for the intracellular fate of the nanomaterials. In this paper, we describe a simple and inexpensive method to process cell monolayers for ultrastructural morphology and immunocytochemistry, ensuring consistent preservation of the cell surface and of the occurring interactions with nanoparticles of different chemical composition.

Small variations in nanoparticle structure dictate differential cellular stress responses and mode of cell death

For optimal exploitation of nanoparticles (NPs) in biomedicine, and to predict nanotoxicity, detailed knowledge of the cellular responses to cell-bound or internalized NPs is imperative. The final outcome of NP-cell interaction is dictated by the type and magnitude of the NP insult and the cellular response. Here, this has been systematically studied by using poly(alkylcyanoacrylate) (PACA) particles differing only in their alkyl side chains; butyl (PBCA), ethylbutyl (PEBCA), or octyl (POCA), respectively. Surprisingly, these highly similar NPs induced different stress responses and modes of cell death in human cell lines. The POCA particles generally induced endoplasmic reticulum stress and apoptosis. In contrast, PBCA and PEBCA particles induced oxidative stress and lipid peroxidation depending on the level of the glutathione precursor cystine and transcription of the cystine transporter SLC7A11. The latter was induced as a protective response by the transcription factors ATF4 and Nrf2. PBCA particles strongly activated ATF4 downstream of the eIF2α kinase HRI, whereas PEBCA particles more potently induced Nrf2 antioxidant responses. Intriguingly, PBCA particles activated the cell death mechanism ferroptosis; a promising option for targeting multidrug-resistant cancers. Our findings highlight that even minor differences in NP composition can severely impact the cellular response to NPs. This may have important implications in therapeutic settings.

Nutraceuticals' Novel Formulations: The Good, the Bad, the Unknown and Patents Involved

Traditional nutraceuticals and cosmeceuticals hold pragmatic nature with respect to their definitions, claims, purposes and marketing strategies. Their definitions are not well established worldwide. They also have different regulatory definitions and registration regulatory processes in different parts of the world. Global prevalence of nutraceuticals and cosmeceuticals is noticeably high with large market share with minimal regulation compared to traditional drugs. The global market is flooded with nutraceuticals and cosmeceuticals claiming to be of natural origin and sold with a therapeutic claim by major online retail stores such as Amazon and eBay. Apart from the traditional formulations, many manufacturers and researchers use novel formulation technologies in nutraceutical and cosmeceutical formulations for different reasons and objectives. Manufacturers tend to differentiate their products with novel formulations to increase market appeal and sales. On the other hand, researchers use novel strategies to enhance nutraceuticals and cosmeceuticals activity and safety. The objective of this review is to assess the current patents and research adopting novel formulation strategies in nutraceuticals and cosmeceuticals. Patents and research papers investigating nutraceutical and cosmeceutical novel formulations were surveyed for the past 15 years. Various nanosystems and advanced biotechnology systems have been introduced to improve the therapeutic efficacy, safety and market appeal of nutraceuticals and cosmeceuticals, including liposomes, polymeric micelles, quantum dots, nanoparticles, and dendrimers. This review provides an overview of nutraceuticals and cosmeceuticals current technologies, highlighting their pros, cons, misconceptions, regulatory definitions and market. This review also aims in separating the science from fiction in the nutraceuticals and cosmeceuticals development, research and marketing.

Guidance on risk assessment of the application of nanoscience and nanotechnologies in the food and feed chain: Part 1, human and animal health

The European Food Safety Authority has produced this Guidance on human and animal health aspects (Part 1) of the risk assessment of nanoscience and nanotechnology applications in the food and feed chain. It covers the application areas within EFSA's remit, e.g. novel foods, food contact materials, food/feed additives and pesticides. The Guidance takes account of the new developments that have taken place since publication of the previous Guidance in 2011. Potential future developments are suggested in the scientific literature for nanoencapsulated delivery systems and nanocomposites in applications such as novel foods, food/feed additives, biocides, pesticides and food contact materials. Therefore, the Guidance has taken account of relevant new scientific studies that provide more insights to physicochemical properties, exposure assessment and hazard characterisation of nanomaterials. It specifically elaborates on physicochemical characterisation of nanomaterials in terms of how to establish whether a material is a nanomaterial, the key parameters that should be measured, the methods and techniques that can be used for characterisation of nanomaterials and their determination in complex matrices. It also details the aspects relating to exposure assessment and hazard identification and characterisation. In particular, nanospecific considerations relating to in vivo/in vitro toxicological studies are discussed and a tiered framework for toxicological testing is outlined. It describes in vitro degradation, toxicokinetics, genotoxicity as well as general issues relating to testing of nanomaterials. Depending on the initial tier results, studies may be needed to investigate reproductive and developmental toxicity, immunotoxicity, allergenicity, neurotoxicity, effects on gut microbiome and endocrine activity. The possible use of read‐across to fill data gaps as well as the potential use of integrated testing strategies and the knowledge of modes/mechanisms of action are also discussed. The Guidance proposes approaches to risk characterisation and uncertainty analysis, and provides recommendations for further research in this area.

This publication is linked to the following EFSA Supporting Publications article: http://onlinelibrary.wiley.com/doi/10.2903/sp.efsa.2018.EN-1430/full

Tissue distribution following 28 day repeated oral administration of aluminum-based nanoparticles with different properties and the in vitro toxicity

The tissue distribution and toxicity of nanoparticles (NPs) depend on their physical and chemical properties both in the manufactured condition and within the biological system. We characterized three types of commercially available aluminum-based NPs (Al-NPs), two rod-type aluminum oxide NPs (Al₂ O₃ , AlONPs), with different aspect ratios (short [S]- and long [L]-AlONPs), and spherical aluminum cerium oxide NPs (AlCeO₃ , AlCeONPs). The surface area was in order of the S-AlONPs > L-AlONPs > AlCeONPs. Very importantly, we found that AlCeONPs is Al₂ O₃ -coated CeO₂ NPs, but not AlCeO₃ NPs, and that the Al level in AlCeONPs is approximately 20% of those in S- and L-AlONPs. All three types of Al-NPs were slightly ionized in gastric fluid and rapidly particlized in the intestinal fluid. There were no significant differences in the body weight gain following 28 days of repeated oral administration of the three different types of Al-NPs. All Al-NPs elevated Al level in the heart, spleen, kidney and blood at 24 hours after the final dose, accompanied by the altered tissue level of redox reaction-related trace elements. Subsequently, in four types of cells derived from the organs which Al-NPs are accumulated, H9C2 (heart), HEK-293 (kidney), splenocytes and RAW264.7 (blood), S-AlONPs showed a very low uptake level and did not exert significant cytotoxicity. Meanwhile, cytotoxicity and uptake level were the most remarkable in cells treated with AlCeONPs. In conclusion, we suggest that the physicochemical properties of NPs should be examined in detail before the release into the market to prevent unexpected adverse health effects.