Studies on the titanium dioxide nanoparticles: biosynthesis, applications and remediation

Toxicity of Carbon, Silicon, and Metal-Based Nanoparticles to Sea Urchin Strongylocentrotus Intermedius

With the increasing annual production of nanoparticles (NPs), the risks of their harmful influence on the environment and human health are rising. However, our knowledge about the mechanisms of interaction between NPs and living organisms is limited. Prior studies have shown that echinoderms, and especially sea urchins, represent one of the most suitable models for risk assessment in environmental nanotoxicology. To the best of the authors’ knowledge, the sea urchin Strongylocentrotus intermedius has not been used for testing the toxicity of NPs. The present study was designed to determine the effect of 10 types of common NPs on spermatozoa activity, egg fertilization, and early stage of embryo development of the sea urchin S. intermedius. In this research, we used two types of multiwalled carbon nanotubes (CNT-1 and CNT-2), two types of carbon nanofibers (CNF-1 and CNF-2), two types of silicon nanotubes (SNT-1 and SNT-2), nanocrystals of cadmium and zinc sulfides (CdS and ZnS), gold NPs (Au), and titanium dioxide NPs (TiO₂). The results of the embryotoxicity test showed the following trend in the toxicity level of used NPs: Au > SNT-2 > SNT-1 > CdS > ZnS > CNF-2 > CNF-1 > TiO₂ > CNT-1 > CNT-2. This research confirmed that the sea urchin S. intermedius can be considered as a sensitive and stable test model in marine nanotoxicology.

Multifunctional titanium dioxide nanoparticles biofabricated via phytosynthetic route using extracts of Cola nitida: antimicrobial, dye degradation, antioxidant and anticoagulant activities

First study of phytosynthesis of TiO₂ NPs using the leaf (KL), pod (KP), seed (KS) and seed shell (KSS) extracts of kola nut tree (Cola nitida) is herein reported. The TiO₂ NPs were characterized and evaluated for their antimicrobial, dye degradation, antioxidant and anticoagulant activities. The nearly spherical-shaped particles had λmax of 272.5–275.0 nm with size range of 25.00–191.41 nm. FTIR analysis displayed prominent peaks at 3446.79, 1639.49 and 1382.96 cm⁻¹, indicating the involvement of phenolic compounds and proteins in the phytosynthesis of TiO₂ NPs. Both SAED and XRD showed bioformation of crystalline anatase TiO₂ NPs which inhibited multidrug-drug resistant bacteria and toxigenic fungi. The catalytic activities of the particles were profound, with degradation of malachite green by 83.48–86.28 % without exposure to UV-irradiation, scavenging of DPPH and H₂O₂by 51.19–60.08 %, and 78.45–99.23 % respectively. The particles as well prevented the coagulation of human blood. In addition to the antimicrobial and dye-degrading activities, we report for the first time the H₂O₂ scavenging and anticoagulant activities of TiO₂ NPs, showing that the particles can be useful for catalytic and biomedical applications.

The Toxicity Phenomenon and the Related Occurrence in Metal and Metal Oxide Nanoparticles: A Brief Review From the Biomedical Perspective

Thousands of different nanoparticles (NPs) involve in our daily life with various origins from food, cosmetics, drugs, etc. It is believed that decreasing the size of materials up to nanometer levels can facilitate their unfavorable absorption since they can pass the natural barriers of live tissues and organs even, they can go across the relatively impermeable membranes. The interaction of these NPs with the biological environment disturbs the natural functions of cells and its components and cause health issues. In the lack of the detailed and comprehensive standard protocols about the toxicity of NPs materials, their control, and effects, this review study focuses on the current research literature about the related factors in toxicity of NPs such as size, concentration, etc. with an emphasis on metal and metal oxide nanoparticles. The goal of the study is to highlight their potential hazard and the advancement of green non-cytotoxic nanomaterials with safe threshold dose levels to resolve the toxicity issues. This study supports the NPs design along with minimizing the adverse effects of nanoparticles especially those used in biological treatments.

Toxicity of Carbon, Silicon, and Metal-Based Nanoparticles to the Hemocytes of Three Marine Bivalves

Simple Summary

The growing nanotechnology industry disposes of a variety of nanoparticles with different physiochemical properties in everyday life. However, the dependence of the safety and toxicity of nanoparticles on their physicochemical properties remains unclear. Bivalve molluscs represent an efficient model for the investigation of nanoparticle toxicity owing to their filtrating ability and feeding on particles suspended in the water. Moreover, the blood cells of bivalve molluscs, the hemocytes, have been suggested as a good analog test-object to mammalian immune cells, phagocytes. In this study, we used hemocytes of three marine bivalve species, namely, Crenomytilus grayanus, Modiolus modiolus, and Arca boucardi, to evaluate and compare the toxic effects of 10 different types of nanoparticles. We gave short-term exposure of the nanoparticles to the hemocytes and registered viability and changes in their cell membrane polarization by employing flow cytometry. Metal-based nanoparticles were the most toxic to the cells of all three tested bivalve mollusc species. However, the sensitivity to different nanoparticle types varied between species. Moreover, the registered cell membrane depolarization indicated an early toxic response and raised concern that chronic long-term exposure of nanoparticles (even if they were previously declared as safe) is a serious threat for aquatic organisms.

Abstract

Nanoparticles (NPs) have broad applications in medicine, cosmetics, optics, catalysis, environmental purification, and other areas nowadays. With increasing annual production of NPs, the risks of their harmful influence on the environment and human health are also increasing. Currently, our knowledge about the mechanisms of the interaction between NPs and living organisms is limited. The marine species and their habitat environment are under continuous stress owing to the anthropogenic activities, which result in the release of NPs in the aquatic environment. We used a bioassay model with hemocytes of three bivalve mollusc species, namely, Crenomytilus grayanus, Modiolus modiolus, and Arca boucardi, to evaluate the toxicity of 10 different types of NPs. Specifically, we compared the cytotoxic effects and cell-membrane polarization changes in the hemocytes exposed to carbon nanotubes, carbon nanofibers, silicon nanotubes, cadmium and zinc sulfides, Au-NPs, and TiO₂ NPs. Viability and the changes in hemocyte membrane polarization were measured by the flow cytometry method. The highest aquatic toxicity was registered for metal-based NPs, which caused cytotoxicity to the hemocytes of all the studied bivalve species. Our results also highlighted different sensitivities of the used tested mollusc species to specific NPs.

Interpreting the role of NO3-, SO42-, and extracellular polymeric substances on aggregation kinetics of CeO2 nanoparticles: Measurement and modeling

The early stage of aggregation of cerium oxide nanoparticles (CeO₂ NPs) in anion solutions was inspected in the absence and presence of extracellular polymeric substance (EPS) with a help of time-resolved dynamic light scattering (DLS). The aggregation kinetics and attachment efficiencies were calculated according to measured hydrodynamic diameter across a range of 1-500 mM NaNO₃ and 0.01-100. mM Na₂SO₄. The aggregation of CeO₂ NPs in both NaNO₃ and Na₂SO₄ solution conformed with the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. In NaNO₃ solution, the critical coagulation concentrations (CCC) of CeO₂ NPs was calculated to be about 47 mM; in Na₂SO₄ solution, CeO₂ NPs showed a re-stabilization process and thus there was no CCC value. SO₄^2- had intenser effects on CeO₂ NPs aggregation than NO₃^- might because of the distinction between their polarization, consisting in Hofmeister series. The presence of bound EPS (B-EPS), tightly bound EPS (TB-EPS) and loosely bound EPS (LB-EPS) in NaNO₃ solutions all lead to significant decrease in CeO₂ NPs aggregation. Steric repulsive force produced by absorbed EPS on CeO₂ NPs might take main responsibility in stabilizing CeO₂ NPs. Besides, Extended Derjaguin-Landau-Verwey-Overbeek (EDLVO) model successfully predicted the energy barrier between CeO₂ NPs with B-EPS, TB-EPS and LB-EPS as a function of NaNO₃ concentration. Furthermore, the difference in impeding the CeO₂ NPs aggregation with B-EPS, TB-EPS and LB-EPS may be caused by the divergence in molecular weight and component mass fraction especially protein content. These results might subserve the assessment on the fate and transport behaviors of CeO₂ NPs released in wastewater treatment plants.

Tetracycline affects the toxicity of P25 n-TiO2 towards marine microalgae Chlorella sp

Pollutants such as n-TiO₂ and tetracycline enter the marine environment through various sources starting from their production until disposal. Hence, it is vital to determine the interactive effect of one pollutant with the other when they coexist in the environment. In the present study, the effect of antibiotic - tetracycline (TC) on the toxicity of P25 n-TiO₂ was studied with marine microalgae, Chlorella sp. The impact of TC (1 mg L^-1) on five different concentrations of n-TiO₂ (0.25, 0.5, 1, 2 and 4 mg L^-1) under both visible and UV-A illuminations was evaluated. Effective diameter of n-TiO₂ in ASW at 0^th h increased from 690.69 ± 19.55 nm (0.25 mg L^-1) to 1183.04 ± 37.10 nm (0.25 mg L^-1 + 1 mg L^-1) and 971.51 ± 14.61 nm (4 mg L^-1) to 1324.12 ± 11.59 nm (4 mg L^-1 + 1 mg L^-1) in presence of TC. A significant increase in the toxicity of 4 mg L^-1 n-TiO₂ upon the addition of TC (68.16 ± 0.37% under visible and 80.21 ± 0.3% under UV-A condition) was observed. No significant difference in toxicity was observed between visible and UV-A illuminations. Further the toxicity data was corroborated through the measurement of oxidative stress and antioxidant enzyme activities. Independent action model showed antagonistic effect for lower concentrations of n-TiO₂ and additive effect for higher concentrations of n-TiO₂ when present in mixture with TC under both illuminations. For the higher mixture concentration of 4 mg L^-1 n-TiO₂ and 1 mg L^-1 TC, the percentage TC removal was about 55.29% and 30% and the corresponding TOC removal was found to be 54.29% and 31.04% under visible and UV-A illuminations respectively. The site of ROS generation in Chlorella sp. was identified with electron transfer chain inhibitors. Both mitochondria and chloroplast acted as the site for the ROS generation in Chlorella sp. The SEM images of the algal cells upon exposure to n-TiO₂ and mixture revealed the aggregation of cells and distortion of cell membrane.

First report on the mutagenicity and cytotoxicity of Zno nanoparticles in reptiles

Understanding how human activities affect animal biodiversity is essential to investigations about the biological effects of several pollutants and contaminants dispersed in the environment. This is the case of zinc oxide nanoparticles (ZnO NPs), which are emerging pollutants whose effect on reptiles' health is completely unknown. Thus, the objective of the present study is to evaluate the possible damages induced by these NPs in Podocnemis expansa juveniles (Amazon turtle) by using morphological changes of circulating erythrocytes as nuclear toxicity biomarker. The animals were exposed to the intramuscular administration of 440 μg/kg and 440,000 μg/kg of ZnO NPs, for 10 consecutive days. The micronuclei assay and other nuclear abnormalities were performed at the end of the experiment, as well as different morphometric measurements applied to the erythrocytes. Based on the current data, ZnO NPs induced nuclear abnormalities such as micronuclei and binucleation, which are associated with carcinogenic processes and with flaws in the mitotic machinery. The low "nuclear area: erythrocyte area" ratio and larger cytoplasmic area observed for animals exposed to NPs evidenced erythrocytic change induction likely related to negative energy balance/metabolism interferences and/or to oxygen transportation efficiency by erythrocytes. This is the first report on the mutagenic and cytotoxic effect induced by NPs on representatives of a group of reptiles. This outcome suggests that further investigations must focus on better understanding the (eco)toxicological potential of ZnO NPs.

In Vitro Toxicity of TiO2:SiO2 Nanocomposites with Different Photocatalytic Properties

The enormous technological relevance of titanium dioxide (TiO2) nanoparticles (NPs) and the consequent concerns regarding potentially hazardous effects that exposure during production, use, and disposal can generate, encourage material scientists to develop and validate intrinsically safe design solution (safe-by-design). Under this perspective, the encapsulation in a silica dioxide (SiO2) matrix could be an effective strategy to improve TiO2 NPs safety, preserving photocatalytic and antibacterial properties. In this work, A549 cells were used to investigate the toxic effects of silica-encapsulated TiO2 having different ratios of TiO2 and SiO2 (1:1, 1:3, and 3:1). NPs were characterized by electron microscopy and dynamic light scattering, and cell viability, oxidative stress, morphological changes, and cell cycle alteration were evaluated. Resulting data demonstrated that NPs with lower content of SiO2 are able to induce cytotoxic effects, triggered by oxidative stress and resulting in cell necrosis and cell cycle alteration. The physicochemical properties of NPs are responsible for their toxicity. Particles with small size and high stability interact with pulmonary cells more effectively, and the different ratio among silica and titania plays a crucial role in the induced cytotoxicity. These results strengthen the need to take into account a safe(r)-by-design approach in the development of new nanomaterials for research and manufacturing.