Effect of the surface texture and crystallinity of ZnO nanoparticles on their toxicity

Magnetic Iron Nanoparticles: Synthesis, Surface Enhancements, and Biological Challenges

This review focuses on the role of magnetic nanoparticles (MNPs), their physicochemical properties, their potential applications, and their association with the consequent toxicological effects in complex biologic systems. These MNPs have generated an accelerated development and research movement in the last two decades. They are solving a large portion of problems in several industries, including cosmetics, pharmaceuticals, diagnostics, water remediation, photoelectronics, and information storage, to name a few. As a result, more MNPs are put into contact with biological organisms, including humans, via interacting with their cellular structures. This situation will require a deeper understanding of these particles’ full impact in interacting with complex biological systems, and even though extensive studies have been carried out on different biological systems discussing toxicology aspects of MNP systems used in biomedical applications, they give mixed and inconclusive results. Chemical agencies, such as the Registration, Evaluation, Authorization, and Restriction of Chemical substances (REACH) legislation for registration, evaluation, and authorization of substances and materials from the European Chemical Agency (ECHA), have held meetings to discuss the issue. However, nanomaterials (NMs) are being categorized by composition alone, ignoring the physicochemical properties and possible risks that their size, stability, crystallinity, and morphology could bring to health. Although several initiatives are being discussed around the world for the correct management and disposal of these materials, thanks to the extensive work of researchers everywhere addressing the issue of related biological impacts and concerns, and a new nanoethics and nanosafety branch to help clarify and bring together information about the impact of nanoparticles, more questions than answers have arisen regarding the behavior of MNPs with a wide range of effects in the same tissue. The generation of a consolidative framework of these biological behaviors is necessary to allow future applications to be manageable.

Phytotoxicity of VO2 nanoparticles with different sizes to pea seedlings

Vanadium dioxide nanoparticles (VO2 NPs) have been massively produced due to their excellent metal-insulator transition characteristics for various applications. Pilot studies indicated the toxicity of VO2 NPs to bacteria and mammalian cells, but the environmental hazards of VO2 NPs to plants have been unrevealed to date. In this study, we reported the inhibitive effects of VO2 NPs to the growth and photosynthesis of pea seedlings. Laboratory synthesized monoclinic VO2 NPs (N-VO2), commercial nanosized VO2 NPs (S-VO2), and commercial microsized VO2 particles (M-VO2) were carefully characterized for environmental toxicity evaluations. VO2 particles were supplemented to culture medium for seed germination and seedling growth. All three VO2 samples did not affect the germination rates of pee seeds, while serious growth inhibition of pea seedlings was observed at 10 mg/L for S-VO2 and N-VO2, and 100 mg/L for M-VO2. VO2 particles had no impact on the chlorophyll contents, but the photosynthesis of leaf was significantly decreased following the consequence of N-VO2 > S-VO2 > M-VO2. The inhibition of photosynthesis was attributed to the damage of acceptor side of photosystem II by VO2 particles at high concentrations. Abundant bioaccumulations of vanadium in roots aroused oxidative damage and changed the root structure. Our results collectively indicated that the phytotoxicity of VO2 NPs was related to the concentration, size and crystalline degree.

Sono-synthesis approach improves anticancer activity of ZnO nanoparticles: reactive oxygen species depletion for killing human osteosarcoma cells

Aim: To investigate the effect of ultrasound during the synthesis of ZnO nanoparticles (NPs) on their anticancer activity. Materials & methods: ZnO NPs were synthesized in the presence and absence of ultrasonic irradiation. Biological tests were performed on human osteosarcoma cancer cells (Saos-2). Results: The sono-synthesized sample indicated higher cytotoxicity than the conventional one. (IC₅₀ = 16.48 ± 0.41 μg/ml for sonochemical ZnO; 26.96 ± 0.33 μg/ml for conventional ZnO). Both sonochemical and conventional samples acted like antioxidants and reduced intracellular reactive oxygen species level. This reduction was more significant in cells treated with the sono-synthesized sample. The sono-synthesized ZnO NPs showed more tumor selectivity than the conventional sample. Conclusion: Sono-synthesis of ZnO NPs by a bath sonicator could improve their anticancer activity.

More serious autophagy can be induced by ZnO nanoparticles than single-walled carbon nanotubes in rat tracheal epithelial cells

Metal oxide nanoparticles and carbon nanoparticles, as common nanoparticles (NPs), can cause autophagy in certain cells, which will lead to biohealth risk issues. This study determined the difference in autophagy induced by zinc oxide nanoparticles (ZnO NPs) and single-walled carbon nanotubes (SWCNTs) in respiratory epithelial cells. ICP-OES results showed that NPs uptake as well as the intercellular contents of particles affected cytotoxicity in a dose-dependent manner. ZnO NPs-30 nm had a distinct green dot structure representing autophagy, the SWCNTs exposure group had a few green light spots at a concentration of 10 μg/L. The ROS content of the ZnO NP-30 nm exposure group had the greatest increase at a concentration of 1000 μg/L, which was 2.5 times higher than that of the control, the SWCNTs exposure group showed a 2.2-fold increase. A slight downregulation of p-mTOR was detected, and the ZnO NPs-30 nm treatment group had the significant downregulation rate. The gene and protein expression levels of Beclin-1 and LC3B were upregulated as the exposure concentration increased. The protein expression of Beclin-1 and LC3B in the 1000 μg/L ZnO NPs-30 nm exposure group were 5.21 times and 4.12 times that of the control, respectively. The mRNA expression of Beclin-1 and LC3B in the 1000 μg/L ZnO NPs-30 nm exposure group were 5.04 times and 3.61 times that of the control, respectively. At any concentration, the effect of ZnO NPs-30 nm was greater than that of the SWCNTs. Interaction and crosstalk analysis showed that exposure to ZnO NPs-30 nm caused autophagy through the aggregation of undegraded autophagosomes, whereas SWCNTs exposure induced diminished intercellular oxidative stress to inhibit autophagy. Therefore, this study demonstrated that the effects of autophagy induced by ZnO NPs-30 nm and SWCNTs were different. The health risks of ZnO-30 nm NPs are higher than those of SWCNTs.

Can the surface modification and/or morphology affect the ecotoxicity of zinc oxide nanomaterials?

Among nanomaterials, zinc oxide (ZnO) is notable for its excellent biocidal properties. In particular, it can be incorporated in mortars to prevent biofouling. However, the morphology of these nanomaterials (NMs) and their impact on the action against biofouling are still unknown. This study aimed to assess how the morphology and surface modification can affect the ecotoxicology of ZnO NMs. The morphologies evaluated were nanoparticles (NPs) and nanorods (NRs), and the ZnO NMs were tested pure and with surface modification through amine functionalization (@AF). The toxic effects of these NMs were evaluated by acute and chronic ecotoxicity tests with the well-established model microcrustacean Daphnia magna. The ZnO NMs were characterized by transmission electron microscopy, X-ray diffraction and infrared spectroscopy. The EC50_48h to D. magna indicated higher acute toxicity of ZnO@AF NRs compared to all tested NMs. Regarding the chronic test with D. magna, high toxic effects on reproduction and longevity were observed with ZnO@AF NRs and effects on growth were observed with ZnO NRs. In general, all tested ZnO NMs presented high toxicity when compared to the positive control, and the NRs presented higher toxicity than NPs in all tested parameters, regardless of the form tested (pure or with surface modification). Additionally, the pathways of ecotoxicity of the tested ZnO NMs was found to be related to combined factors of Zn ion release, effective diameter of particles and NM internalization in the organism.

Incineration of Nanoclay Composites Leads to Byproducts with Reduced Cellular Reactivity

Addition of nanoclays into a polymer matrix leads to nanocomposites with enhanced properties to be used in plastics for food packaging applications. Because of the plastics' high stored energy value, such nanocomposites make good candidates for disposal via municipal solid waste plants. However, upon disposal, increased concerns related to nanocomposites' byproducts potential toxicity arise, especially considering that such byproducts could escape disposal filters to cause inhalation hazards. Herein, we investigated the effects that byproducts of a polymer polylactic acid-based nanocomposite containing a functionalized montmorillonite nanoclay (Cloisite 30B) could pose to human lung epithelial cells, used as a model for inhalation exposure. Analysis showed that the byproducts induced toxic responses, including reductions in cellular viability, changes in cellular morphology, and cytoskeletal alterations, however only at high doses of exposure. The degree of dispersion of nanoclays in the polymer matrix appeared to influence the material characteristics, degradation, and ultimately toxicity. With toxicity of the byproduct occurring at high doses, safety protocols should be considered, along with deleterious effects investigations to thus help aid in safer, yet still effective products and disposal strategies.

DLS and zeta potential - What they are and what they are not?

Adequate characterization of NPs (nanoparticles) is of paramount importance to develop well defined nanoformulations of therapeutic relevance. Determination of particle size and surface charge of NPs are indispensable for proper characterization of NPs. DLS (dynamic light scattering) and ZP (zeta potential) measurements have gained popularity as simple, easy and reproducible tools to ascertain particle size and surface charge. Unfortunately, on practical grounds plenty of challenges exist regarding these two techniques including inadequate understanding of the operating principles and dealing with critical issues like sample preparation and interpretation of the data. As both DLS and ZP have emerged from the realms of physical colloid chemistry - it is difficult for researchers engaged in nanomedicine research to master these two techniques. Additionally, there is little literature available in drug delivery research which offers a simple, concise account on these techniques. This review tries to address this issue while providing the fundamental principles of these techniques, summarizing the core mathematical principles and offering practical guidelines on tackling commonly encountered problems while running DLS and ZP measurements. Finally, the review tries to analyze the relevance of these two techniques from translatory perspective.

Toxicity of metal oxide nanoparticles: mechanisms, characterization, and avoiding experimental artefacts

Metal oxide nanomaterials are widely used in practical applications and represent a class of nanomaterials with the highest global annual production. Many of those, such as TiO2 and ZnO, are generally considered non-toxic due to the lack of toxicity of the bulk material. However, these materials typically exhibit toxicity to bacteria and fungi, and there have been emerging concerns about their ecotoxicity effects. The understanding of the toxicity mechanisms is incomplete, with different studies often reporting contradictory results. The relationship between the material properties and toxicity appears to be complex and diifficult to understand, which is partly due to incomplete characterization of the nanomaterial, and possibly due to experimental artefacts in the characterization of the nanomaterial and/or its interactions with living organisms. This review discusses the comprehensive characterization of metal oxide nanomaterials and the mechanisms of their toxicity.