Online monitoring of cell metabolism to assess the toxicity of nanoparticles: The case of cobalt ferrite

Toxicity of different-sized cobalt ferrite (CoFe2O4) nanoparticles to Oncorhynchus mykiss at early development stages

As innovative and versatile agents with potential applications in a wide range of fields including medicine, electronics, wastewater treatment, cosmetics, and energy storage devices, magnetic nanoparticles (NPs) are significant attention. However, our knowledge of the harmful effects of different-sized NPs, particularly of their effects on aquatic animals, is limited. In this study, we evaluated the impact of different-sized (sub-2, 5, and 15 nm) cobalt ferrite (CoFe2O4) NPs on the biological parameters of rainbow trout (Oncorhynchus mykiss) embryos and larvae. The NPs were characterized using techniques such as high-resolution transmission electron microscopy (HRTEM) for imaging, X-ray diffraction (XRD) for crystallographic analysis, and energy-dispersive X-ray spectroscopy (EDX) for elemental analysis, and were tested for impact through a series of toxicity, genotoxicity, and biochemical assays at a concentration of 100 mg/L. The obtained results showed that toxicity of CoFe2O4 NPs depended on the size of NPs and the developmental stage of the fish. Our results, which revealed significant changes in biological parameters of O. mykiss under exposure to CoFe2O4 NPs, imply that these NPs may be not environmentally safe. The hierarchical cluster analysis showed that embryos of the control group were clearly separated from those exposed to NPs of various sizes. However, in the exposed larvae, the effects of control and the smallest-sized NPs (sub-2 nm) differed from those induced by larger NPs (5 nm and 15 nm). Additional research is necessary to comprehend the mechanisms underlying the observed variations, which would be advantageous for both managing the risk of NPs to humans and advancing the field of aquatic nanotoxicology.

Hybrid magnetic nanoparticles as efficient nanoheaters in biomedical applications

Heating at the nanoscale is the basis of several biomedical applications, including magnetic hyperthermia therapies and heat-triggered drug delivery. The combination of multiple inorganic materials in hybrid magnetic nanoparticles provides versatile platforms to achieve an efficient heat delivery upon different external stimuli or to get an optical feedback during the process. However, the successful design and application of these nanomaterials usually require intricate synthesis routes and their magnetic response is still not fully understood. In this review we give an overview of the novel systems reported in the last few years, which have been mostly obtained by organic phase-based synthesis and epitaxial growth processes. Since the heating efficiency of hybrid magnetic nanoparticles often relies on the exchange-interaction between their components, we discuss various interface-phenomena that are responsible for their magnetic properties. Finally, followed by a brief comment on future directions in the field, we outline recent advances on multifunctional nanoparticles that can boost the heating power with light and combine heating and temperature sensing in a single nanomaterial.

Interference: A Much-Neglected Aspect in High-Throughput Screening of Nanoparticles

Despite several studies addressing nanoparticle (NP) interference with conventional toxicity assay systems, it appears that researchers still rely heavily on these assays, particularly for high-throughput screening (HTS) applications in order to generate "big" data for predictive toxicity approaches. Moreover, researchers often overlook investigating the different types of interference mechanisms as the type is evidently dependent on the type of assay system implemented. The approaches implemented in the literature appear to be not adequate as it often addresses only one type of interference mechanism with the exclusion of others. For example, interference of NPs that have entered cells would require intracellular assessment of their interference with fluorescent dyes, which has so far been neglected. The present study investigated the mechanisms of interference of gold NPs and silver NPs in assay systems implemented in HTS including optical interference as well as adsorption or catalysis. The conventional assays selected cover all optical read-out systems, that is, absorbance (XTT toxicity assay), fluorescence (CytoTox-ONE Homogeneous membrane integrity assay), and luminescence (CellTiter Glo luminescent assay). Furthermore, this study demonstrated NP quenching of fluorescent dyes also used in HTS (2',7'-dichlorofluorescein, propidium iodide, and 5,5',6,6'-tetrachloro-1,1',3,3'-tetraethyl-benzamidazolocarbocyanin iodide). To conclude, NP interference is, as such, not a novel concept, however, ignoring this aspect in HTS may jeopardize attempts in predictive toxicology. It should be mandatory to report the assessment of all mechanisms of interference within HTS, as well as to confirm results with label-free methodologies to ensure reliable big data generation for predictive toxicology.

Biophysical Characterization of (Silica-coated) Cobalt Ferrite Nanoparticles for Hyperthermia Treatment

Magnetic hyperthermia is a technique that describes the heating of material through an external magnetic field. Classic hyperthermia is a medical condition where the human body overheats, being usually triggered by a heat stroke, which can lead to severe damage to organs and tissue due to the denaturation of cells. In modern medicine, hyperthermia can be deliberately induced to specified parts of the body to destroy malignant cells. Magnetic hyperthermia describes the way that this overheating is induced and it has the inherent advantage of being a minimal invasive method when compared to traditional surgery methods. This work presents a particle system that offers huge potential for hyperthermia treatments, given its good loss value, i.e., the particles dissipate a lot of heat to their surroundings when treated with an ac magnetic field. The measurements were performed in a low-cost custom hyperthermia setup. Additional toxicity assessments on Jurkat cells show a very low short-term toxicity on the particles and a moderate low toxicity after two days due to the prevalent health concerns towards nanoparticles in organisms.

Exchange Coupling in Soft Magnetic Nanostructures and Its Direct Effect on Their Theranostic Properties

Exchange coupling between hard and soft magnetic materials at the nanoscale exhibits novel or improved physical properties for energy and data storage applications. Recently, exchange coupling has also been explored in core/shell magnetic nanostructures (MNS) composed of hard and soft magnetic spinel ferrites, but applications have been limited in biomedicine due to the presence of "toxic" cobalt based ferrites as hard magnetic component. We report core/shell MNS where both core and shell components are soft magnetic ferrites (Fe₃O₄, MnFe₂O₄, and Zn_0.2Mn_0.8Fe₂O₄) and show that exchange coupling still exists due to the difference in their anisotropy. The physical properties (saturation magnetization, susceptibility, anisotropy, r₂ relaxivity, and specific absorption rate) of core/shell MNS are compared with the same size single phase counterparts which excludes any size dependent effect and gives the direct effect of exchange coupling. After optimization of core and shell components and their proportions, we have shown that a core/shell MNS shows significantly higher contrast enhancement and thermal activation properties than their single phase counterparts due to exchange coupling between core and shell ferrites. Our finding provides a novel way to improve theranostic properties of spinel ferrite based MNS while maintaining their biocompatibility.

In Vitro Evaluation of the Toxicity of Cobalt Ferrite Nanoparticles in Kidney Cell

Objectives

The remarkable properties of hard magnetic cobalt ferrite nanoparticles (CoFe₂O₄-NPs) and their physicochemical stability lead to various applications in different industrial and medical fields. Although CoFe₂O₄-NPs have been reported to cause toxic effects, there is a serious lack of information concerning their effects on the kidneys. In this study, it was aimed to investigate the toxic effects of CoFe₂O₄-NPs on NRK-52E kidney cells.

Materials and Methods

The particle characterisation and cellular uptake were determined using transmission electron microscopy, dynamic light scattering and inductively coupled plasma-mass spectrometry. Then, the cytotoxicity was evaluated by MTT and neutral red uptake assays, the genotoxicity by comet assay, and the apoptotic potentials by Annexin V-FITC apoptosis detection assay with propidium iodide.

Results

After 24 h exposure to CoFe₂O₄-NPs (39±17 nm), it was observed they did not affect the cell viability at concentration ranging from 100 to 1000 µg/mL, but significantly induced DNA damage at concentration ≤100 µg/mL. No apoptotic or necrotic effect was observed in the exposed cells.

Conclusion

According to the results obtained, CoFe₂O₄-NPs are promising for safe use in various applications. However, further in vivo studies are needed to fully understand their mechanisms of action.

In Vitro Toxicological Assessment of Cobalt Ferrite Nanoparticles in Several Mammalian Cell Types

Nanoparticles have been widely used in various fields due to the superior physicochemical properties and functions. As a result, human exposure to nanoparticles increases dramatically. Previous researches have shown that nanoparticles could travel through the respiratory, digestive system, or skin into the blood and then to the secondary organs such as the brain, heart, and liver. Besides, the nanoparticle toxicity is controversial and dependent on the sensitivity of the cell type, route of exposure, and condition, as well as their characteristics. Similarly, cobalt ferrite nanoparticles (CoFe₂O₄-NPs) have been used in different industrial fields, and have also various application possibilities in medical and biomedical fields. CoFe₂O₄-NPs induce toxic responses in various organisms such as human, mice, and algae. However, there is a serious deficit of information concerning their effects on human health and the environment. We aimed to investigate the toxic effects of CoFe₂O₄-NPs on liver (HepG2), colon (Caco-2), lung (A549), and neuron (SH-SY5Y) cells, which reflect different exposure routes in vitro, by using various toxicological endpoints. The cytotoxicity, genotoxicity, oxidative damage, and apoptosis induction of CoFe₂O₄-NPs (39 ± 17 nm) were evaluated. After 24 h, the nanoparticles decreased cell viability at ≤100 μg/mL, while increasing viability at >100 μg/mL. CoFe₂O₄-NPs induced DNA and oxidative damage with increased malondialdehyde (MDA) and 8-hydroxy deoxyguanosine (8-OHdG) levels and decreased glutathione (GSH) levels with no change in protein carbonyl (PC) levels. CoFe₂O₄-NPs had apoptotic effect in HepG2 and Caco-2 cells in a concentration-dependent manner and necrotic effects on SH-SY5Y and A549 cells. Consequently, the adverse effects of CoFe₂O₄-NPs should raise concern about their safety in consumer products.

Nanotoxicological study of polyol-made cobalt-zinc ferrite nanoparticles in rabbit

The increasing use of engineered nanomaterials in commercial manufacturing and consumer products presents an important toxicological concern. Superparamagnetic zinc-cobalt ferrite nanoparticles (SFN) emerge as a promising tool for early cancer diagnostics and targeted therapy. However, toxicity and biological activities of SFN should be evaluated in vitro and in vivo in animal before any clinical application. In this study we aim to synthesize and characterize such objects using polyol process in order to assess its nanotoxicological profile in vitro as well as in vivo. The produced particles consist of a cobalt-zinc ferrite phase corresponding to the Zn0.8Co0.2Fe2O4 composition. They are isotropic in shape single crystals of 8nm in size. The thermal variation of their dc-magnetization confirms their superparamagnetic behavior. In vitro, acute exposure (4h) to them (100μgmL(-1)) induced an important decrease of healthy Human Umbilical Vein Endothelial Cells (HUVECs) viability. In vivo investigation in New-Zealand rabbits revealed that they lead to tissue toxicities; in lungs, liver and kidneys. Our investigations report, for the first time as far as we know, that SFN exhibit harmful properties in human cells and mammals.

Systematic elucidation of interactive unfolding and corona formation of bovine serum albumin with cobalt ferrite nanoparticles

Nanoparticles (NPs) are extensively being used in modern nano-based therapies and nano-protein formulations.

Impact of nanoparticles on human and environment: review of toxicity factors, exposures, control strategies, and future prospects

Nanotechnology has revolutionized the world through introduction of a unique class of materials and consumer products in many arenas. It has led to production of innovative materials and devices. Despite of their unique advantages and applications in domestic and industrial sectors, use of materials with dimensions in nanometers has raised the issue of safety for workers, consumers, and human environment. Because of their small size and other unique characteristics, nanoparticles have ability to harm human and wildlife by interacting through various mechanisms. We have reviewed the characteristics of nanoparticles which form the basis of their toxicity. This paper also reviews possible routes of exposure of nanoparticles to human body. Dermal contact, inhalation, and ingestion have been discussed in detail. As very limited data is available for long-term human exposures, there is a pressing need to develop the methods which can determine short and long-term effects of nanoparticles on human and environment. We also discuss in brief the strategies which can help to control human exposures to toxic nanoparticles. We have outlined the current status of toxicological studies dealing with nanoparticles, accomplishments, weaknesses, and future challenges.

An aqueous method for the controlled manganese (Mn2+) substitution in superparamagnetic iron oxide nanoparticles for contrast enhancement in MRI

Despite the success in the use of superparamagnetic iron oxide nanoparticles (SPION) for various scientific applications, its potential in biomedical fields has not been exploited to its full potential.

Magnetic nanoparticle clusters as actuators of ssDNA release

One of the major areas of research in nanomedicine is the design of drug delivery systems with remotely controllable release of the drug. Despite the enormous progress in the field, this aspect still poses a challenge, especially in terms of selectivity and possible harmful interactions with biological components other than the target. We report an innovative approach for the controlled release of DNA, based on clusters of core-shell magnetic nanoparticles. The primary nanoparticles are functionalized with a single-stranded oligonucleotide, whose pairing with a half-complementary strand in solution induces clusterization. The application of a low frequency (6 KHz) alternating magnetic field induces DNA melting with the release of the single strand that induces clusterization. The possibility of steering and localizing the magnetic nanoparticles, and magnetically actuating the DNA release discloses new perspectives in the field of nucleic-acid based therapy.

Label-free in vitro toxicity and uptake assessment of citrate stabilised gold nanoparticles in three cell lines

Background

Reliable in vitro toxicity testing is needed prior to the commencement of in vivo testing necessary for hazard identification and risk assessment of nanoparticles. In this study, the cytotoxicity and uptake of 14 nm and 20 nm citrate stabilised gold nanoparticles (AuNPs) in the bronchial epithelial cell line BEAS-2B, the Chinese hamster ovary cell line CHO, and the human embryonic kidney cell line HEK 293 were investigated.

Methods

Cytotoxicity of the AuNPs was assessed via traditional XTT-, LDH-, and ATP-based assays, followed by cell impedance studies. Dark-field imaging and hyperspectral imaging were used to confirm the uptake of AuNPs into the cells.

Results

Interference of the AuNPs with the XTT- and ATP-based assays was overcome through the use of cell impedance technology. AuNPs were shown to be relatively non-toxic using this methodology; nevertheless CHO cells were the most sensitive cell type with 20 nm AuNPs having the highest toxicity. Uptake of both 14 nm and 20 nm AuNPs was observed in all cell lines in a time- and cell type-dependent manner.

Conclusions

Using the cell impedance and dark-field hyperspectral imaging technologies, it was possible to study the toxicity of AuNPs in different cell lines and show that these cells could internalize AuNPs with their subsequent intracellular aggregation. It was also possible to show that this toxicity would not correlate with the level of uptake but it would correlate with cell-type and the size of the AuNPs. Therefore, these two label-free methodologies used in this study are suitable for in vitro studies on the effects of AuNPs, and could present themselves as appropriate and valuable methodologies for future nanoparticle toxicity and uptake studies.

Size-dependent toxicity and cell interaction mechanisms of gold nanoparticles on mouse fibroblasts

Gold nanoparticles (AuNPs) are currently used in several fields including biomedical applications, although no conclusive information on their cytotoxicity is available. For this reason this work has investigated the effects of AuNPs in vitro on Balb/3T3 mouse fibroblasts. Results obtained exposing cells for 72 h to AuNPs 5 and 15 nm citrate stabilized, revealed cytotoxic effects only for AuNPs 5 nm at concentration ≥ 50 μM if measured by colony forming efficiency (CFE). To understand the differences in cytotoxicity observed for the two AuNPs sizes, we investigated the uptake and the intracellular distribution of the nanoparticles. By TEM it was observed that 5 and 15 nm AuNPs are internalized by Balb/3T3 cells and located within intracellular endosomal compartments. Quantification of the uptake by ICP-MS showed that AuNPs internalization enhanced even up to 72 h. Disruption of the actin cytoskeleton was evident, with cell footprints narrow and contracted; effects more remarkable in cells exposed to 5 nm AuNP. The mechanism of NPs cell internalization was investigated using immunocytochemistry and western blot. No significant effect was observed in the expression level of caveolin, while reduction of the expression and degradation of the clathrin heavy chain was observed in cells exposed for 72 h to AuNPs.

Real-time monitoring of photocytotoxicity in nanoparticles-based photodynamic therapy: a model-based approach

Nanoparticles are widely suggested as targeted drug-delivery systems. In photodynamic therapy (PDT), the use of multifunctional nanoparticles as photoactivatable drug carriers is a promising approach for improving treatment efficiency and selectivity. However, the conventional cytotoxicity assays are not well adapted to characterize nanoparticles cytotoxic effects and to discriminate early and late cell responses. In this work, we evaluated a real-time label-free cell analysis system as a tool to investigate in vitro cyto- and photocyto-toxicity of nanoparticles-based photosensitizers compared with classical metabolic assays. To do so, we introduced a dynamic approach based on real-time cell impedance monitoring and a mathematical model-based analysis to characterize the measured dynamic cell response. Analysis of real-time cell responses requires indeed new modeling approaches able to describe suited use of dynamic models. In a first step, a multivariate analysis of variance associated with a canonical analysis of the obtained normalized cell index (NCI) values allowed us to identify different relevant time periods following nanoparticles exposure. After light irradiation, we evidenced discriminant profiles of cell index (CI) kinetics in a concentration- and light dose-dependent manner. In a second step, we proposed a full factorial design of experiments associated with a mixed effect kinetic model of the CI time responses. The estimated model parameters led to a new characterization of the dynamic cell responses such as the magnitude and the time constant of the transient phase in response to the photo-induced dynamic effects. These parameters allowed us to characterize totally the in vitro photodynamic response according to nanoparticle-grafted photosensitizer concentration and light dose. They also let us estimate the strength of the synergic photodynamic effect. This dynamic approach based on statistical modeling furnishes new insights for in vitro characterization of nanoparticles-mediated effects on cell proliferation with or without light irradiation.

Multifunctional Peptide-conjugated hybrid silica nanoparticles for photodynamic therapy and MRI

Photodynamic therapy (PDT) is an emerging theranostic modality for various cancer as well as non-cancer diseases. Its efficiency is mainly based on a selective accumulation of PDT and imaging agents in tumor tissue. The vascular effect is widely accepted to play a major role in tumor eradication by PDT. To promote this vascular effect, we previously demonstrated the interest of using an active- targeting strategy targeting neuropilin-1 (NRP-1), mainly over-expressed by tumor angiogenic vessels. For an integrated vascular-targeted PDT with magnetic resonance imaging (MRI) of cancer, we developed multifunctional gadolinium-based nanoparticles consisting of a surface-localized tumor vasculature targeting NRP-1 peptide and polysiloxane nanoparticles with gadolinium chelated by DOTA derivatives on the surface and a chlorin as photosensitizer. The nanoparticles were surface-functionalized with hydrophilic DOTA chelates and also used as a scaffold for the targeting peptide grafting. In vitro investigations demonstrated the ability of multifunctional nanoparticles to preserve the photophysical properties of the encapsulated photosensitizer and to confer photosensitivity to MDA-MB-231 cancer cells related to photosensitizer concentration and light dose. Using binding test, we revealed the ability of peptide-functionalized nanoparticles to target NRP-1 recombinant protein. Importantly, after intravenous injection of the multifunctional nanoparticles in rats bearing intracranial U87 glioblastoma, a positive MRI contrast enhancement was specifically observed in tumor tissue. Real-time MRI analysis revealed the ability of the targeting peptide to confer specific intratumoral retention of the multifunctional nanoparticles.

Multi-sensor arrays for online monitoring of cell dynamics in in vitro studies with choroid plexus epithelial cells

Sensors and multi-sensor arrays are the basis of new technologies for the non-label monitoring of cell activity. In this paper we show that choroid plexus cells can be cultured on silicon chips and that sensors register in real time changes in their activity, constituting an interesting experimental paradigm for cell biology and medical research. To validate the signals recorded (metabolism = peri-cellular acidification, oxygen consumption = respiration; impedance = adhesion, cell shape and motility) we performed experiments with compounds that act in a well-known way on cells, influencing these parameters. Our in vitro model demonstrates the advantages of multi-sensor arrays in assessment and experimental characterization of dynamic cellular events—in this case in choroid plexus functions, however with applicability to other cell types as well.