In vitro developmental toxicity test detects inhibition of stem cell differentiation by silica nanoparticles

Comparative assessment of embryotoxicity of 2,4,6-triiodophenol to mouse blastoid and pre-implantation embryo models

Embryonic developmental effects of disinfection by-products, which are generated during drinking water treatment and widely detected in environment, have gained more and more attention nowadays, calling for construction of in vitro research models which can mimic early embryonic development to evaluate the embryotoxicity. The embryonic stem cell test offers a promising assay to predict embryotoxicity of environmental pollutions. However, it is not appropriate for the toxicological study of preimplantation embryos. Here, we used mouse extended stem cells (mEPS) to reconstruct embryo-like structures (blastoid), furtherly attempting to evaluate the reliability of this model for the prediction of possible developmental toxicity of 2,4,6-triiodophenol (TIP, 5-50 μM), a novel halogenated disinfection byproduct widely detected in water and even drinking water, to mammalian preimplantation embryo. To verify this, we treated mouse embryo derived from in vitro fertilization (IVF-embryo) as reference. The results showed that mEPS-blastoid was like natural blastocyst in morphology, cell composition, and could recapitulate key developmental events happened during mouse preimplantation stage. When blastoid and IVF-embryo models were separately exposed to TIP, their final blastocyst formation rates were not impaired, according to morphological features, meanwhile that TIP exposure caused slight cell apoptosis. Besides, TIP induced an ICM cell bias in cell fate decision, resulting in cell proportion change, which implied abnormal developmental potential. Though we could not evaluate TIP's embryotoxicity before 8-cell stage using blastoid model, its viability as a novel and high-throughput assessment platform for increasing environmental pollutants was still recognized.

Effects of antimicrobial metal nanoparticles on characteristics and function properties of mouse mesenchymal stem cells

Nanoparticles (NPs) have a wide use in various field of industry and in medicine, where they represent a promise for their antimicrobial effects. Simultaneous application of NPs and therapeutic stem cells can speed up tissue regeneration and improve healing process but there is a danger of negative impacts of NPs on stem cells. Therefore, we tested effects of four types of metal antimicrobial NPs on characteristics and function properties of mouse mesenchymal stem cells (MSCs) in vitro. All types of tested NPs, i.e. zinc oxide, silver, copper oxide and titanium dioxide, exerted negative effects on the expression of phenotypic markers, metabolic activity, differentiation potential, expression of genes for immunoregulatory molecules and on production of cytokines and growth factors by MSCs. However, there were apparent differences in the impact of individual types of NPs on tested characteristics and function properties of MSCs. The results showed that individual types of NPs influence the activity of MSCs, and thus the use of metal NPs during tissue regeneration and in combination with stem cell therapy should be well considered.

The Impact of Metal Nanoparticles on the Immunoregulatory and Therapeutic Properties of Mesenchymal Stem Cells

Negative impacts of nanomaterials on stem cells and cells of the immune system are one of the main causes of an impaired or slowed tissue healing. Therefore, we tested effects of four selected types of metal nanoparticles (NPs): zinc oxide (ZnO), copper oxide (CuO), silver (Ag), and titanium dioxide (TiO₂) on the metabolic activity and secretory potential of mouse mesenchymal stem cells (MSCs), and on the ability of MSCs to stimulate production of cytokines and growth factors by macrophages. Individual types of nanoparticles differed in the ability to inhibit metabolic activity, and significantly decreased the production of cytokines and growth factors (interleukin-6, vascular endothelial growth factor, hepatocyte growth factor, insulin-like growth factor-1) by MSCs, with the strongest inhibitory effect of CuO NPs and the least effect of TiO₂ NPs. The recent studies indicate that immunomodulatory and therapeutic effects of transplanted MSCs are mediated by macrophages engulfing apoptotic MSCs. We co-cultivated macrophages with heat-inactivated MSCs which were untreated or were preincubated with the highest nontoxic concentrations of metal NPs, and the secretory activity of macrophages was determined. Macrophages cultivated in the presence of both untreated MSCs or MSCs preincubated with NPs produced significantly enhanced and comparable levels of various cytokines and growth factors. These results suggest that metal nanoparticles inhibit therapeutic properties of MSCs by a direct negative effect on their secretory activity, but MSCs cultivated in the presence of metal NPs have preserved the ability to stimulate cytokine and growth factor production by macrophages.

In Vivo Cellular Magnetic Imaging: Labeled vs. Unlabeled Cells

Superparamagnetic iron oxide (SPIO)-labeling of cells has been applied for magnetic resonance imaging (MRI) cell tracking for over 30 years, having resulted in a dozen or so clinical trials. SPIO nanoparticles are biodegradable and can be broken down into elemental iron, and hence the tolerance of cells to magnetic labeling has been overall high. Over the years, however, single reports have accumulated demonstrating that the proliferation, migration, adhesion and differentiation of magnetically labeled cells may differ from unlabeled cells, with inhibition of chondrocytic differentiation of labeled human mesenchymal stem cells (hMSCs) as a notable example. This historical perspective provides an overview of some of the drawbacks that can be encountered with magnetic labeling. Now that magnetic particle imaging (MPI) cell tracking is emerging as a new in vivo cellular imaging modality, there has been a renaissance in the formulation of SPIO nanoparticles this time optimized for MPI. Lessons learned from the occasional past pitfalls encountered with SPIO-labeling of cells for MRI may expedite possible future clinical translation of (combined) MRI/MPI cell tracking.

An Overview of Essential Microelements and Common Metallic Nanoparticles and Their Effects on Male Fertility

Numerous factors affect reproduction, including stress, diet, obesity, the use of stimulants, or exposure to toxins, along with heavy elements (lead, silver, cadmium, uranium, vanadium, mercury, arsenic). Metals, like other xenotoxins, can cause infertility through, e.g., impairment of endocrine function and gametogenesis or excess production of reactive oxygen species (ROS). The advancement of nanotechnology has created another hazard to human safety through exposure to metals in the form of nanomaterials (NMs). Nanoparticles (NPs) exhibit a specific ability to penetrate cell membranes and biological barriers in the human body. These ultra-fine particles (<100 nm) can enter the human body through the respiratory tract, food, skin, injection, or implantation. Once absorbed, NPs are transported to various organs through the blood or lymph. Absorbed NPs, thanks to ultrahigh reactivity compared to bulk materials in microscale size, disrupt the homeostasis of the body as a result of interaction with biological molecules such as DNA, lipids, and proteins; interfering with the functioning of cells, organs, and physiological systems; and leading to severe pathological dysfunctions. Over the past decades, much research has been performed on the reproductive effects of essential trace elements. The research hypothesis that disturbances in the metabolism of trace elements are one of the many causes of infertility has been unquestionably confirmed. This review examines the complex reproductive risks for men regarding the exposure to potentially harmless xenobiotics based on a series of 298 articles over the past 30 years. The research was conducted using PubMed, Web of Science, and Scopus databases searching for papers devoted to in vivo and in vitro studies related to the influence of essential elements (iron, selenium, manganese, cobalt, zinc, copper, and molybdenum) and widely used metallic NPs on male reproduction potential.

A toxicological profile of silica nanoparticles

Humans are regularly exposed to silica nanoparticles in environmental and occupational contexts, and these exposures have been implicated in the onset of adverse health effects. Existing reviews on silica nanoparticle toxicity are few and not comprehensive. There are natural and synthetic sources by which crystalline and amorphous silica nanoparticles are produced. These processes influence physiochemical properties, which are factors that can dictate toxicological effects. Toxicological assessment includes exposure scenario (e.g. environmental, occupational), route of exposure, toxicokinetics, and toxicodynamics. Broader considerations include pathology, risk assessment, regulation, and treatment after injury. This review aims to consolidate the most relevant and up-to-date research in these areas to provide an exhaustive toxicological profile of silica nanoparticles.

Advantages and prospects of stem cells in nanotoxicology

Nanomaterials have been widely used in many fields, especially in biomedical and stem cell therapy. However, the potential risks associated with nanomaterials applications are also gradually increasing. Therefore, effective and robust toxicology models are critical to evaluate the developmental toxicity of nanomaterials. The development of stem cell research provides a new idea of developmental toxicology. Recently, many researchers actively investigated the effects of nanomaterials with different sizes and surface modifications on various stem cells (such as embryonic stem cells (ESCs), adult stem cells, etc.) to study the toxic effects and toxic mechanisms. In this review, we summarized the effects of nanomaterials on the proliferation and differentiation of ESCs, mesenchymal stem cells and neural stem cells. Moreover, we discussed the advantages of stem cells in nanotoxicology compared with other cell lines. Finally, combined with the latest research methods and new molecular mechanisms, we analyzed the application of stem cells in nanotoxicology.

The impact of environmental water on the potential application of core-shell titania-silica nanospheres as photocatalysts

In this study, the core-shell silica nanospheres modified with titanium dioxide were tested in the photocatalytic decomposition of dyes. The presented data underlines the advantages and shortcomings in the potential application of silica-based catalysts to neutralize organic pollutants. During the photocatalytic reaction in distilled water, catalysts showed decreased efficiency due to a carbon layer deposited on its surface. This finding set an additional goal to investigate the possibility of regenerating the photocatalyst. Studies have shown that the catalyst could be successfully reused following the thermal removal of deposited carbon.Furthermore, the reactivated silica-titania catalysts exhibited comparable photocatalytic performance to the newly made nanomaterial. Surprisingly, catalyst application in the river water eventually resulted in the permanent deactivation of silica-titania nanospheres, which was caused by the interchangeable silica dissolution/precipitation process on the surface of the studied nanomaterial. In environmental water, silica dissolves and precipitates on titanium dioxide's surface, blocking the interaction between organic compounds and TiO₂. The deactivation occurring in the environmental samples is irreversible. In distilled water, the decomposition of organic compounds leads to photocatalysts' deactivation by forming a carbon layer on their surface. Reactivation of the silica-based photocatalyst after distilled water is achievable by annealing at a high temperature. In light of our findings, the combination of the photocatalytic properties of TiO₂and the silica template shows no prospects in the purification of polluted waste or environmental water.

Global Proteomics to Study Silica Nanoparticle-Induced Cytotoxicity and Its Mechanisms in HepG2 Cells

Silica nanoparticles (SiO₂ NPs) are commonly used in medical and pharmaceutical fields. Research into the cytotoxicity and overall proteomic changes occurring during initial exposure to SiO₂ NPs is limited. We investigated the mechanism of toxicity in human liver cells according to exposure time [0, 4, 10, and 16 h (h)] to SiO₂ NPs through proteomic analysis using mass spectrometry. SiO₂ NP-induced cytotoxicity through various pathways in HepG2 cells. Interestingly, when cells were exposed to SiO₂ NPs for 4 h, the morphology of the cells remained intact, while the expression of proteins involved in mRNA splicing, cell cycle, and mitochondrial function was significantly downregulated. These results show that the toxicity of the nanoparticles affects protein expression even if there is no change in cell morphology at the beginning of exposure to SiO₂ NPs. The levels of reactive oxygen species changed significantly after 10 h of exposure to SiO₂ NPs, and the expression of proteins associated with oxidative phosphorylation, as well as the immune system, was upregulated. Eventually, these changes in protein expression induced HepG2 cell death. This study provides insights into cytotoxicity evaluation at early stages of exposure to SiO₂ NPs through in vitro experiments.

Comparative cytotoxicity studies of halophenolic disinfection byproducts using human extended pluripotent stem cells

2,4,6-trichlorophenol (TCP), 2,4,6-tribromophenol (TBP) and 2,4,6-triiodophenol (TIP) are a new class of halophenolic disinfection byproducts (DBPs) which have been widely detected in drinking water. In recent years, their developmental toxicity has got increasing public attention due to their potential toxic effects on embryo development towards lower organisms. Nonetheless, the application of human embryos for embryonic toxicologic studies is rendered by ethical and moral considerations, as well as the technical barrier to sustaining normal development beyond a few days. Human extended pluripotent stem (EPS) cells (novel totipotent-like stem cells) represent a much more appropriate cellular model for studying human embryo development. In this study, we utilized human EPS cells to study the developmental toxicity of TCP, TBP and TIP, respectively. All three halophenolic DBPs showed cytotoxicity against human EPS cells in an obvious dose-dependent manner, among which TIP was the most cytotoxic one. Notably, the expression of pluripotent genes in human EPS cells significantly declined after 2,4,6-trihalophenol exposure. Meanwhile, 2,4,6-trihalophenol exposure promoted ectodermal differentiation of human EPS cells in an embryoid bodies (EBs) differentiation assay, while both endodermal and mesodermal differentiation were impaired. These results implied that phenolic halogenated DBPs have specific effects on human embryo development even in the early stage of pregnancy. In summary, we applied human EPS cells as a novel research model for human embryo developmental toxicity study of environmental pollutants, and demonstrated the toxicity of phenolic halogenated DBPs on early embryo development of human beings.

The Size-dependent Cytotoxicity of Amorphous Silica Nanoparticles: A Systematic Review of in vitro Studies

With the increasing production and application of engineered amorphous silica nanoparticles (aSiNPs), people have more opportunities to be exposed to aSiNPs. However, the knowledge of its adverse health effects and related mechanisms is still limited, compared with the well-studied crystalline micron-sized silica. Since small differences in the physical–chemical properties of nanoparticles could cause significant differences in the toxic effect, it is important to distinguish how these variations influence the outcoming toxicity. Notably, particle size, as one of the essential characterizations of aSiNPs, is relevant to its biological activities. Thus, the aim of this systematic review was to summarize the relationship between the particle size of aSiNPs and its adverse biological effects. In order to avoid the influence of complicated in vivo experimental conditions on the toxic outcome, only in vitro toxicity studies which reported on the cytotoxic effect of different sizes aSiNPs were included. After the systematic literature retrieval, selection, and quality assessment process, 76 eligible scientific papers were finally included in this review. There were 76% of the studies that concluded a size-dependent cytotoxicity of aSiNPs, in which smaller-sized aSiNPs possessed greater toxicity. However, this trend could be modified by certain influence factors, such as the synthetic method of aSiNPs, particle aggregation state in cell culture medium, toxicity endpoint detection method, and some other experimental conditions. The effects of these influence factors on the size-dependent cytotoxicity of aSiNPs were also discussed in detail in the present review.

Toxicity Evaluation of Nanostructured Silica Orally Administered to Rats: Influence on Immune System Function

The experimental data on the oral toxicity of nanostructured amorphous silica (SiO₂), widely used in food supplements, pharmaceuticals, and cosmetics, in terms of its in vivo effect on the immune system, are contradictory. Therefore, this study aimed to assess the rat's immune function after SiO₂ oral administration. In the first experiment, SiO₂ was daily orally administered to Wistar rats for 92 days in doses of 0.1, 1.0, 10, and 100 mg/kg of body weight (bw). In the second 28-day experiment, SiO₂ in a dose of 100 mg/kg bw was daily orally administered to rats parenterally immunized with the food allergen ovalbumin (OVA) for the reproduction of systemic anaphylaxis reaction. Together with integral indices, we assessed intestinal permeability to protein macromolecules; hematology; CD45RA+, CD3+, CD4+, CD8+, and CD161a+ cells; cytokines TNF-α, IL-6, and IL-10; and IgG to OVA. The results obtained showed that SiO₂ has no effect on the severity of the anaphylactic reaction, but is capable inducing a toxic effect on the T-cell immune systems of rats. Estimated no observed adverse effect level NOAEL for SiO₂ ranges up to 100 mg/kg bw in terms of its daily consumption for 1-3 months. Using SiO₂ as a food additive should be the subject of regulation.

Potential Use of Silica Nanoparticles for the Microbial Stabilisation of Wine: An In Vitro Study Using Oenococcus oeni as a Model

The emerging trend towards the reduction of SO2 in winemaking has created a need to look for alternative methods to ensure the protection of wine against the growth of undesired species of microorganisms and to safely remove wine microorganisms. This study describes the possible application of silica nanospheres as a wine stabilisation agent, with Oenococcus oeni (DSM7008) as a model strain. The experiment was conducted firstly on model solutions of phosphate-buffered saline and 1% glucose. Their neutralising effect was tested under stirring with the addition of SiO2 (0.1, 0.25, and 0.5 mg/mL). Overall, the highest concentration of nanospheres under continuous stirring resulted in the greatest decrease in cell counts. Transmission electron microscope (TEM) and scanning electron microscopy (SEM) analyses showed extensive damage to the bacterial cells after stirring with silica nanomaterials. Then, the neutralising effect of 0.5 mg/mL SiO2 was tested in young red wine under stirring, where cell counts were reduced by over 50%. The obtained results suggest that silica nanospheres can serve as an alternative way to reduce or substitute the use of sulphur dioxide in the microbial stabilisation of wine. In addition, further aspects of following investigations should focus on the protection against enzymatic and chemical oxidation of wine.

An automated and high-throughput-screening compatible pluripotent stem cell-based test platform for developmental and reproductive toxicity assessment of small molecule compounds

The embryonic stem cell test (EST) represents the only validated and accepted in vitro system for the detection and classification of compounds according to their developmental and reproductive teratogenic potency. The widespread implementation of the EST, however, in particular for routine application in pharmaceutical development, has not been achieved so far. Several drawbacks still limit the high-throughput screening of potential drug candidates in this format: The long assay period, the use of non-homogeneous viability assays, the low throughput analysis of marker protein expression and the compatibility of the assay procedures to automation. We have therefore introduced several advancements into the EST workflow: A reduction of the assay period, an introduction of homogeneous viability assays, and a straightforward analysis of marker proteins by flow cytometry and high content imaging to assess the impact of small molecules on differentiation capacity. Most importantly, essential parts of the assay procedure have been adapted to lab automation in 96-well format, thus enabling the interrogation of several compounds in parallel. In addition, extensive investigations were performed to explore the predictive capacity of this next-generation EST, by testing a set of well-known embryotoxicants that encompasses the full range of chemical-inherent embryotoxic potencies possible. Due to these significant improvements, the augmented workflow provides a basis for a sensitive, more rapid, and reproducible high throughput screening compatible platform to predict in vivo developmental toxicity from in vitro data which paves the road towards application in an industrial setting.

Graphical abstract

Reactive Oxygen Species-Related Nanoparticle Toxicity in the Biomedical Field

The unique physicochemical characteristics of nanoparticles have recently gained increasing attention in a diverse set of applications, particularly in the biomedical field. However, concerns about the potential toxicological effects of nanoparticles remain, as they have a higher tendency to generate excessive amounts of reactive oxygen species (ROS). Due to the strong oxidation potential, the excess ROS induced by nanoparticles can result in the damage of biomolecules and organelle structures and lead to protein oxidative carbonylation, lipid peroxidation, DNA/RNA breakage, and membrane structure destruction, which further cause necrosis, apoptosis, or even mutagenesis. This review aims to give a summary of the mechanisms and responsible for ROS generation by nanoparticles at the cellular level and provide insights into the mechanics of ROS-mediated biotoxicity. We summarize the literature on nanoparticle toxicity and suggest strategies to optimize nanoparticles for biomedical applications.

Cytotoxic and Genotoxic Assessment of Silicon Dioxide Nanoparticles by Allium and Comet Tests

Silicon nanoparticles gained a great interest due to its use in biomedical research. It is considered as safe and has been used in nanomedicine. But literature still states its toxicity depending upon the size and dose of silicon nanoparticles. So, current study was aimed to evaluate the cytotoxicity and genotoxicity of silicon dioxide nanoparticles (SiO₂NPs) by Allium anaphase-telophase and Comet tests. Characterization of SiO₂NPs showed the particle size as 16.12 ± 3.07 nm. The mean diameter of SiO₂NPs was having range of 404.66 ± 93.39 nm in solution. Highest total anomalies (18.80 ± 0.45) were observed at 100 µg/mL, whereas least (11.2 ± 0.84) were observed by the 12.5 µg/mL concentration. There was concentration-response association in increased CAs and DNA damage. The highest concentration (100 µg/mL) of SiO₂NPs induced the significant DNA damage (149.67 ± 1.15), whereas the least was observed by the negative control (2.67 ± 0.58). The current study revealed the cytotoxic and genotoxic effects of SiO₂NPs on the root meristem cells of A. cepa.

Advances and controversies in studying sunscreen delivery and toxicity

This review critically evaluates the sunscreen delivery and toxicity field. We chose to focus on approved sunscreens in this review. Optimal sunscreen use prevents skin cancer and photoageing but there is an important knowledge gap in sunscreen/skin interactions. Sunscreen delivery is a key for efficacy, but studying sunscreen delivery is not straightforward. We review the strengths and weaknesses of in vitro, excised skin and clinical approaches. Understanding positive and negative sunscreen effects on skin homeostasis is also challenging. The results in this field, especially in vitro testing, are controversial and experimental design varies widely which further supports disparities between some findings. We hypothesize that bias towards showing sunscreen toxicity to increase impact could be problematic. We explore that perception through a detailed review of experimental design, especially in cell culture models. Our conclusion is that emerging, non- and minimally invasive technologies are enabling new approaches to volunteer studies that could significantly improve knowledge of sunscreen delivery and interactions.

Microarray-assisted size-effect study of amorphous silica nanoparticles on human bronchial epithelial cells

Amorphous silica nanoparticles (SiNPs) are not only abundant in nature, but also the second largest engineering nanomaterials in terms of annual output. Respiratory exposure is the main route for SiNPs to enter the human body. A large number of studies have focused on the respiratory toxicity of SiNPs and demonstrated that SiNPs could induce pulmonary tissue damage, inflammation, fibrosis, and even the malignant transformation of bronchial epithelial cells, while the size-dependent toxicity of SiNPs and their underlying biological mechanisms remain unclear. In this regard, a transcriptomics study would be conductive to gaining a better understanding of the toxic mechanism. In the present study, microarray analysis was performed to investigate the genome-wide transcriptional alteration induced by different sizes of SiNPs in human primary bronchial epithelial cells (BEAS-2B). To determine the effect of the particle size on the toxicity, nanoparticles of two sizes (41 nm and 61 nm) and submicron particles of one size (206 nm) were introduced. The bioinformatics analysis results indicated that: (1) the number of differentially expressed genes in the three SiNP-treated groups increased with the particle size decreasing; (2) the genes involved in the immune and inflammatory response, gene expression, signal transduction, endoplasmic reticulum stress, oxidative stress, cell metabolism, and cell proliferation were gradually upregulated with the particle size decreasing, while the genes related to the morphological development of the respiratory system were gradually downregulated with the particle size decreasing; (3) the modes of action of the two nanoparticles overlapped with each other to some degree, and there existed many different modes compared to those from the submicron particles; (4) both the silica nanoparticles affected the pathways associated with the cell entry of silica nanoparticles, autophagy and lysosomal dysfunction, endoplasmic reticulum stress, inflammatory response, DNA damage, and gene expression, as well as apoptotic resistance and cancer. To the best of our knowledge, this is the first study that has reported the alteration trend of gene expression profiles with the change in silica particle size. Our study provides a great deal of information on the toxic mechanisms underlying the respiratory toxicity induced by SiNPs, and can also serve as an experimental basis for the toxicity and safety evaluation of silica nanoparticles.

Comparative analysis of honey and citrate stabilized gold nanoparticles: In vitro interaction with proteins and toxicity studies

Gold nanoparticles of comparable size were synthetized using honey mediated green method (AuNPs@honey) and citrate mediated Turkevich method (AuNPs@citrate). Their colloidal behavior in two cell media DMEM and RPMI, both supplemented with 10% FBS, was systematically investigated with different characterization techniques in order to evidence how the composition of the media influences their stability and the development of protein/NP complex. We revealed the formation of the protein corona which individually covers the nanoparticles in RPMI media, like a dielectric spacer according to UV-Vis spectroscopy, while DMEM promotes more abundant agglomerations, clustering together the nanoparticles, according to TEM investigations. In order to evaluate the biological impact of nanoparticles, B16 melanoma and L929 mouse fibroblasts cells were used to carry out the viability assays. Generally, the L929 cells were more sensitive than B16 cells to the presence of gold nanoparticles. Measurements of cell viability, proliferation and apoptotic activities of B16 cells indicated that the effects induced by AuNPs@honey were slightly similar to those induced by AuNPs@citrate, however, the toxic response improved in the L929 fibroblast cells following the treatment with AuNPs@honey within the same concentration range from 1 μg/ml to 15 μg/ml for 48 h. Results showed that honey mediated synthesis generates nanoparticles with reduced toxicity trends depending on the cell type, concentration of nanoparticles and exposure time toward various biomedical applications.

Effect of Fluoride Doping in Laponite Nanoplatelets on Osteogenic Differentiation of Human Dental Follicle Stem Cells (hDFSCs)

Bioactive nanosilicates are emerging prominent next generation biomaterials due to their intrinsic functional properties such as advanced biochemical and biophysical cues. Recent studies show interesting dose-dependent effect of fluoride ions on the stem cells. Despite of interesting properties of fluoride ions as well as nanosilicate, there is no reported literature on the effect of fluoride-doped nanosilicates on stem cells. We have systematically evaluated the interaction of fluoride nanosilicate platelets (NS + F) with human dental follicle stem cells (hDFSCs) to probe the cytotoxicity, cellular transport (internalization) and osteogenic differentiation capabilities in comparison with already reported nanosilicate platelets without fluoride (NS − F). To understand the osteoinductive and osteoconductive properties of the nanosilicate system, nanosilicate treated hDFSCs are cultured in three different medium namely normal growth medium, osteoconductive medium, and osteoinductive medium up to 21 d. NS + F treated stem cells show higher ALP activity, osteopontin levels and significant alizarin red staining compared to NS − F treated cells. This study highlights that the particles having fluoride additives (NS + F) aid in enhancing the osteogenic differentiation capabilities of hDFSCs thus potential nanobiomaterial for periodontal bone tissue regeneration.

Investigation of toxicological effects of amorphous silica nanostructures with amine-functionalized surfaces on Vero cells

Amorphous silica (SiO₂) nanostructures are described in the literature as having low toxicity and are widely used in many industrial products. However, surface modifications, such as amine-functionalization, can result in increased cytotoxicity. In this study, amorphous SiO₂ nanostructures (SiO₂ NS) were synthesized and amine-functionalized with two different amine molecules: primary (SiO₂ NS@1) and tri-amine (SiO₂ NS@3). The materials were characterized by transmission electron microscopy (TEM), zeta potential (ZP), effective diameter (ED) and surface area measurements, X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The toxicity of the three SiO₂ NS samples toward Vero cells was evaluated. According to the methyl thiazolyl tetrazolium (MTT) assay, the IC_50,24h was 1.477 ± 0.12 g L^-1 for SiO₂ NS, 0.254 ± 0.07 g L^-1 for SiO₂ NS@1 and 0.117 ± 0.05 g L^-1 for SiO₂ NS@3. The order of cytotoxicity was SiO₂ NS@3 > SiO₂ NS@1 » SiO₂ NS. There was an increase in malondialdehyde (MDA) levels and ROS productions in the cells exposed to all three materials. Also, TEM images showed damage on the mitochondria and rough endoplasmic reticulum.

Murine exposure to gold nanoparticles during early pregnancy promotes abortion by inhibiting ectodermal differentiation

Background

Gold nanoparticles (AuNPs) have been widely studied for biomedical applications, although their safety and potential toxicity in pregnancy remains unknown. The aim of this study is to explore the effect of AuNPs maternal exposure at different gestational ages on fetal survival and development, as well as the potential mechanism of AuNPs affecting embryos and fetuses.

Methods

Thirty nm polyethylene glycol (PEG)-coated AuNPs (A30) were administered to pregnant mice via intravenous injection (5 μg Au/g body weight) over three days at either early or late pregnancy. Fetal abortion rate and morphological development in E16.5 were then detected in detail. The pregnant mice physiological states with A30 exposure were examined by biochemical, histological or imaging methods; and materno-fetal distribution of gold elements was assayed by electron microscopy and mass spectrometry. Murine embryonic stem cells derived embryoid-bodies or neuroectodermal cells were treated with A30 (0.0025 to 0.25 μg Au/mL) to examine A30 effects on expression levels of the germ differentiation marker genes. Tukey’s method was used for statistical analysis.

Results

Exposure to A30 during early (A30E) but not late (A30L) pregnancy caused a high abortion rate (53.5%), lower fetal survival rate and abnormal decidualization compared with non-exposed counterparts. The developmental damage caused by A30 followed an “all-or-nothing” pattern, as the non-aborted fetuses developed normally and pregnancies maintained normal endocrine values. A30 caused minor impairment of liver and kidney function of A30E but not A30L mice. TEM imaging of fetal tissue sections confirmed the transfer of A30 into fetal brain and live as aggregates. qPCR assays showed A30 suppressed the expression of ectodermal, but not mesodermal and endodermal differentiation markers.

Conclusions

These results illustrate that maternal A30 exposure in early pregnant results in A30 transfer into embryonic tissues, inhibiting ectodermal differentiation of embryonic stem cells, leading to abnormal embryonic development and abortion. While exposure to A30 during late pregnancy had little or no impact on dams and fetuses. These findings suggest the safety of biomedical applications employing AuNPs during pregnancy is strongly influenced by fetal maturity and gestational age at exposure and provide the clues for AuNPs safe application period in pregnancy.

Electronic supplementary material

The online version of this article (10.1186/s10020-018-0061-2) contains supplementary material, which is available to authorized users.

Luminescent silica mesoparticles for protein transduction

Unlike silica nanoparticles, the potential of silica mesoparticles (SMPs) (i.e. particles of submicron size) for biological applications in particular the in vitro (let alone in vivo) cellular delivery of biological cargo has so far not been sufficiently studied. Here we examine the potential of luminescent (namely, octahedral molybdenum cluster doped) SMPs synthesised by a simple one-pot reaction for the labelling of cells and for protein transduction into larynx carcinoma (Hep-2) cells using GFP as a model protein. Our data demonstrates that the SMPs internalise into the cells within half an hour. This results in cells that detectably luminesce via conventional methods. In addition, the particles are non-toxic both in darkness and upon photo-irradiation. The SMPs were modified to allow their functionalisation by a protein, which then delivered the protein (GFP) efficiently into the cells. Thus, the luminescent SMPs offer a cheap and trackable alternative to existing materials for cellular internalisation of proteins, such as the HIV TAT protein and commercial protein delivery agents (e.g. Pierce™).

Pluripotent Stem Cells in Developmental Toxicity Testing: A Review of Methodological Advances

Millions of children are born each year with a birth defect. Many of these defects are caused by environmental factors, although the underlying etiology is often unknown. In vivo mammalian models are frequently used to determine if a chemical poses a risk to the developing fetus. However, there are over 80 000 chemicals registered for use in the United States, many of which have undergone little safety testing, necessitating the need for higher-throughput methods to assess developmental toxicity. Pluripotent stem cells (PSCs) are an ideal in vitro model to investigate developmental toxicity as they possess the capacity to differentiate into nearly any cell type in the human body. Indeed, a burst of research has occurred in the field of stem cell toxicology over the past decade, which has resulted in numerous methodological advances that utilize both mouse and human PSCs, as well as cutting-edge technology in the fields of metabolomics, transcriptomics, transgenics, and high-throughput imaging. Here, we review the wide array of approaches used to detect developmental toxicants, suggest areas for further research, and highlight critical aspects of stem cell biology that should be considered when utilizing PSCs in developmental toxicity testing.

Quantitative Proteomics Study Reveals Changes in the Molecular Landscape of Human Embryonic Stem Cells with Impaired Stem Cell Differentiation upon Exposure to Titanium Dioxide Nanoparticles

The increasing number of nanoparticles (NPs) being used in various industries has led to growing concerns of potential hazards that NP exposure can incur on human health. However, its global effects on humans and the underlying mechanisms are not systemically studied. Human embryonic stem cells (hESCs), with the ability to differentiate to any cell types, provide a unique system to assess cellular, developmental, and functional toxicity in vitro within a single system highly relevant to human physiology. Here, the quantitative proteomics approach is adopted to evaluate the molecular consequences of titanium dioxide NPs (TiO₂ NPs) exposure in hESCs. The study identifies ≈328 unique proteins significantly affected by TiO₂ NPs exposure. Proteomics analysis highlights that TiO₂ NPs can induce DNA damage, elevated oxidative stress, apoptotic responses, and cellular differentiation. Furthermore, in vivo analysis demonstrates remarkable reduction in the ability of hESCs in teratoma formation after TiO₂ NPs exposure, suggesting impaired pluripotency. Subsequently, it is found that TiO₂ NPs can disrupt hESC mesoderm differentiation into cardiomyocytes. The study unveils comprehensive changes in the molecular landscape of hESCs by TiO₂ NPs and identifies the impact which TiO₂ NPs can have on the pluripotency and differentiation properties of human stem cells.

Electrospun nanofibers decorated with bio-sonochemically synthesized gold nanoparticles as an ultrasensitive probe in amalgam-based mercury (II) detection system

In this study, bio-ultrasound-assisted synthesized gold nanoparticles using Gracilaria canaliculata algae have been immobilized on a polymeric support and used as a glassy probe chemosensor for detection and rapid removal of Hg²⁺ ions. The function of the suggested chemosensor has been explained based on gold-amalgam formation and its catalytic role on the reaction of sodium borohydride and rhodamine B (RhB) with fluorescent and colorimetric sensing function. The catalyzed reduction of RhB by the gold amalgam led to a distinguished color change from red and yellow florescence to colorless by converting the amount of Hg²⁺ deposited on Au-NPs. The detection limit of the colorimetric and fluorescence assays for Hg²⁺ was 2.21 nM and 1.10 nM respectively. By exposing the mentioned colorless solution to air for at least 2 h, unexpectedly it was observed that the color and fluorescence of RhB were restored. Have the benefit of the above phenomenon a recyclable and portable glass-based sensor has been provided by immobilizing the Au-NPs and RB on the glass slide using electrospinning. Moreover, the introduced combinatorial membrane has facilitated the detection and removal of Hg²⁺ ions in various Hg (II)-contaminated real water samples with efficiency of up to 99%.

SiO2 nanoparticles modulate the electrical activity of neuroendocrine cells without exerting genomic effects

Engineered silica nanoparticles (NPs) have attracted increasing interest in several applications, and particularly in the field of nanomedicine, thanks to the high biocompatibility of this material. For their optimal and controlled use, the understanding of the mechanisms elicited by their interaction with the biological target is a prerequisite, especially when dealing with cells particularly vulnerable to environmental stimuli like neurons. Here we have combined different electrophysiological approaches (both at the single cell and at the population level) with a genomic screening in order to analyze, in GT1-7 neuroendocrine cells, the impact of SiO₂ NPs (50 ± 3 nm in diameter) on electrical activity and gene expression, providing a detailed analysis of the impact of a nanoparticle on neuronal excitability. We find that 20 µg mL⁻¹ NPs induce depolarization of the membrane potential, with a modulation of the firing of action potentials. Recordings of electrical activity with multielectrode arrays provide further evidence that the NPs evoke a temporary increase in firing frequency, without affecting the functional behavior on a time scale of hours. Finally, NPs incubation up to 24 hours does not induce any change in gene expression.

Effective Labeling of Primary Somatic Stem Cells with BaTiO3 Nanocrystals for Second Harmonic Generation Imaging

While nanoparticles are an increasingly popular choice for labeling and tracking stem cells in biomedical applications such as cell therapy, their intracellular fate and subsequent effect on stem cell differentiation remain elusive. To establish an effective stem cell labeling strategy, the intracellular nanocrystal concentration should be minimized to avoid adverse effects, without compromising the intensity and persistence of the signal necessary for long-term tracking. Here, the use of second-harmonic generating barium titanate nanocrystals is reported, whose achievable brightness allows for high contrast stem cell labeling with at least one order of magnitude lower intracellular nanocrystals than previously reported. Their long-term photostability enables to investigate quantitatively at the single cell level their cellular fate in hematopoietic stem cells (HSCs) using both multiphoton and electron microscopy. It is found that the concentration of nanocrystals in proliferative multipotent progenitors is over 2.5-fold greater compared to quiescent stem cells; this difference vanishes when HSCs enter a nonquiescent, proliferative state, while their potency remains unaffected. Understanding the nanoparticle stem cell interaction allows to establish an effective and safe nanoparticle labeling strategy into somatic stem cells that can critically contribute to an understanding of their in vivo therapeutic potential.

Relevance to investigate different stages of pregnancy to highlight toxic effects of nanoparticles: The example of silica

Amorphous silica nanoparticles (SiO₂NPs) have been recognized as safe nanomaterial, hence their use in biomedical applications has been explored. Data, however, suggest potential toxicity of SiO₂ NPs in pregnant individuals. However, no studies relating nanoparticle biokinetic/toxicity to the different gestational stages are currently available. In this respect, we have investigated the possible embryotoxic effects of three-size and two-surface functionalization SiO₂NPs in mice. After intravenous administration of different concentrations at different stages of pregnancy, clinical and histopathological evaluations, performed close to parturition, did not show signs of maternal toxicity, nor effects on placental/fetal development, except for amino-functionalized 25 nm NPs. Biodistribution was studied by ICP-AES 24 h after administration, and demonstrates that all particles distributed to placenta and conceptuses/fetuses, although size, surface charge and gestational stage influenced biodistribution. Our data suggest the need of comprehensive toxicological studies, covering the entire gestation to reliably assess the safety of nanoparticle exposure during pregnancy.

Nanomaterials modulate stem cell differentiation: biological interaction and underlying mechanisms

Stem cells are unspecialized cells that have the potential for self-renewal and differentiation into more specialized cell types. The chemical and physical properties of surrounding microenvironment contribute to the growth and differentiation of stem cells and consequently play crucial roles in the regulation of stem cells’ fate. Nanomaterials hold great promise in biological and biomedical fields owing to their unique properties, such as controllable particle size, facile synthesis, large surface-to-volume ratio, tunable surface chemistry, and biocompatibility. Over the recent years, accumulating evidence has shown that nanomaterials can facilitate stem cell proliferation and differentiation, and great effort is undertaken to explore their possible modulating manners and mechanisms on stem cell differentiation. In present review, we summarize recent progress in the regulating potential of various nanomaterials on stem cell differentiation and discuss the possible cell uptake, biological interaction and underlying mechanisms.

Interfacial Hydrogen Bonds and Their Influence Mechanism on Increasing the Thermal Stability of Nano-SiO₂-Modified Meta-Aramid Fibres

For further analysis of the effect of nano-doping on the properties of high polymers and research into the mechanism behind modified interfacial hydrogen bonds, a study on the formation probability of nano-SiO₂/meta-aramid fibre interfacial hydrogen bonds and the strengthening mechanism behind interfacial hydrogen bonds on the thermal stability of meta-aramid fibres using molecular dynamics is performed in this paper. First, the pure meta-aramid fibre and nano-SiO₂/meta-aramid fibre mixed models with nanoparticle radiuses of 3, 5, 7 and 9 Å (1 Å = 10-1 nm) are built, and then the optimization process and dynamics simulation of the models are conducted. The dynamics simulation results indicate that the number of hydrogen bonds increase due to the doping by nano-SiO₂ and that the number of interfacial hydrogen bonds increases with the nanoparticle radius. By analysing the hydrogen bond formation probability of all the atom pairs in the mixed model with pair correlation functions (PCFs), it can be observed that the hydrogen bond formation probability between the oxygen atom and hydrogen atom on the nanoparticle surface is the greatest. An effective way to increase the number of interfacial hydrogen bonds in nano-SiO₂ and meta-aramid fibres is to increase the number of hydrogen atoms on the nano-silica surface and oxygen atoms in the meta-aramid fibre. By using the radial distribution function (RDF), the conclusion can be further drawn that the hydrogen bond formation probability is at a maximum when the atomic distance is 2.7⁻2.8 Å; therefore, increasing the number of atoms within this range can significantly increase the formation probability of hydrogen bonds. According to the results of chain movement, the existence of interfacial hydrogen bonds effectively limits the free movement of the molecular chains of meta-aramid fibres and enhances the thermal stability of meta-aramid fibres. The existence of interfacial hydrogen bonds is one of the important reasons for formation of the stable interface structure between nanoparticles and meta-aramid fibres. In addition, a nanoparticle with a small radius improves the interfacial hydrogen bond energy density and interfacial interaction energy density, enhancing the stability of the mixed model interface.

Molecular and immunological toxic effects of nanoparticles

Nanoparticles have emerged as a boon for the public health applications such as drug delivery, diagnostic, and imaging. Biodegradable and non-bio degradable nanoparticles have been used at a large scale level to increase the efficiency of the biomedical process at the cellular, animal and human level. Exponential use of nanoparticles reinforces the adverse immunological changes at the human health level. Physical and chemical properties of nanoparticles often lead to a variety of immunotoxic effects such as activation of stress-related genes, membrane disruption, and release of pro-inflammatory cytokines. Delivered nanoparticles in animal or human interact with various components of the immune system such as lymphocytes, macrophages, neutrophils etc. Nanoparticles delivered above the threshold level damages the cellular physiology by the generation of reactive oxygen and nitrogen species. This review article represents the potential of nanoparticles in the field of nanomedicine and provides the critical evidence which leads to develop immunotoxicity in living cells and organisms by altering immunological responses.

Quantitative Analysis of Hepatic Toxicity in Rats Induced by Inhalable Silica Nanoparticles Using Acoustic Radiation Force Imaging

OBJECTIVES

The purposes of this study were to verify whether inhalable silicon dioxide (SiO₂ ) nanoparticles could induce hepatic injury and to investigate the relationship between the exposure time and SiO₂ nanoparticle dosage by using acoustic radiation force impulse imaging (ARFI).

METHODS

A total of 72 rats were randomly separated into 9 groups with 8 in each: blank control group, 0.9% normal saline group, polyacrylate (PPE) group, 25%, 50%, and 100% SiO₂ groups, and 25%, 50%, and 100% SiO₂ /PPE groups with inhaled SiO₂ nanoparticle concentrations similar to the SiO₂ groups. After successful modeling and design, the hepatic shear wave velocity (SWV) values of the 9 groups were obtained on days 3, 7, 14, 21, and 28 by using ARFI, and the intragroup and intergroups differences in the SWVs were compared. The serum alanine aminotransferase (ALT) and aspartate aminotransferase were tested and compared on day 28. Hepatic tissues were collected for histologic observation on day 28.

RESULTS

The pathologic results verified that inhalable SiO₂ nanoparticles could induce hepatic injury. Compared with the control group, the hepatic SWV and serum ALT values in the SiO₂ groups and SiO₂ /PPE groups were elevated (P < .05). The dosage and exposure time of SiO₂ played a key role in the elevation of the SWV in the SiO₂ and SiO₂ /PPE groups. The correlation between the ALT level and SWV was significant on day 28 (P < .05).

CONCLUSIONS

Inhalable SiO₂ nanoparticles and SiO₂ /PPE were able to induce hepatic injury in rats. Using ARFI to evaluate hepatic toxicity induced by SiO₂ nanoparticles was effective in this study.

Modelling the toxicity of a large set of metal and metal oxide nanoparticles using the OCHEM platform

Inorganic nanomaterials have become one of the new areas of modern knowledge and technology and have already found an increasing number of applications. However, some nanoparticles show toxicity to living organisms, and can potentially have a negative influence on environmental ecosystems. While toxicity can be determined experimentally, such studies are time consuming and costly. Computational toxicology can provide an alternative approach and there is a need to develop methods to reliably assess Quantitative Structure-Property Relationships for nanomaterials (nano-QSPRs). Importantly, development of such models requires careful collection and curation of data. This article overviews freely available nano-QSPR models, which were developed using the Online Chemical Modeling Environment (OCHEM). Multiple data on toxicity of nanoparticles to different living organisms were collected from the literature and uploaded in the OCHEM database. The main characteristics of nanoparticles such as chemical composition of nanoparticles, average particle size, shape, surface charge and information about the biological test species were used as descriptors for developing QSPR models. QSPR methodologies used Random Forests (WEKA-RF), k-Nearest Neighbors and Associative Neural Networks. The predictive ability of the models was tested through cross-validation, giving cross-validated coefficients q² = 0.58-0.80 for regression models and balanced accuracies of 65-88% for classification models. These results matched the predictions for the test sets used to develop the models. The proposed nano-QSPR models and uploaded data are freely available online at http://ochem.eu/article/103451 and can be used for estimation of toxicity of new and emerging nanoparticles at the early stages of nanomaterial development.

Toxicity of nano- and ionic silver to embryonic stem cells: a comparative toxicogenomic study

BACKGROUND

The widespread application of silver nanoparticles (AgNPs) and silver-containing products has raised public safety concerns about their adverse effects on human health and the environment. To date, in vitro toxic effects of AgNPs and ionic silver (Ag+) on many somatic cell types are well established. However, no studies have been conducted hitherto to evaluate their effect on cellular transcriptome in embryonic stem cells (ESCs).

RESULTS

The present study characterized transcriptomic changes induced by 5.0 µg/ml AgNPs during spontaneous differentiation of mouse ESCs, and compared them to those induced by Ag+ under identical conditions. After 24 h exposure, 101 differentially expressed genes (DEGs) were identified in AgNP-treated cells, whereas 400 genes responded to Ag+. Despite the large differences in the numbers of DEGs, functional annotation and pathway analysis of the regulated genes revealed overall similarities between AgNPs and Ag+. In both cases, most of the functions and pathways impacted fell into two major categories, embryonic development and metabolism. Nevertheless, a number of canonical pathways related to cancer were found for Ag+ but not for AgNPs. Conversely, it was noted that several members of the heat shock protein and the metallothionein families were upregulated by AgNPs but not Ag+, suggesting specific oxidative stress effect of AgNPs in ESCs. The effects of AgNPs on oxidative stress and downstream apoptosis were subsequently confirmed by flow cytometry analysis.

CONCLUSIONS

Taken together, the results presented in the current study demonstrate that both AgNPs and Ag+ caused transcriptomic changes that could potentially exert an adverse effect on development. Although transcriptomic responses to AgNPs and Ag+ were substantially similar, AgNPs exerted specific effects on ESCs due to their nanosized particulate form.

The safety of nanostructured synthetic amorphous silica (SAS) as a food additive (E 551)

KEY MESSAGES

Particle sizes of E 551 products are in the micrometre range. The typical external diameters of the constituent particles (aggregates) are greater than 100 nm. E 551 does not break down under acidic conditions such as in the stomach, but may release dissolved silica in environments with higher pH such as the intestinal tract. E 551 is one of the toxicologically most intensively studied substances and has not shown any relevant systemic or local toxicity after oral exposure. Synthetic amorphous silica (SAS) meeting the specifications for use as a food additive (E 551) is and has always been produced by the same two production methods: the thermal and the wet processes, resulting in E 551 products consisting of particles typically in the micrometre size range. The constituent particles (aggregates) are typically larger than 100 nm and do not contain discernible primary particles. Particle sizes above 100 nm are necessary for E 551 to fulfil its technical function as spacer between food particles, thus avoiding the caking of food particles. Based on an in-depth review of the available toxicological information and intake data, it is concluded that the SAS products specified for use as food additive E 551 do not cause adverse effects in oral repeated-dose studies including doses that exceed current OECD guideline recommendations. In particular, there is no evidence for liver toxicity after oral intake. No adverse effects have been found in oral fertility and developmental toxicity studies, nor are there any indications from in vivo studies for an immunotoxic or neurotoxic effect. SAS is neither mutagenic nor genotoxic in vivo. In intact cells, a direct interaction of unlabelled and unmodified SAS with DNA was never found. Differences in the magnitude of biological responses between pyrogenic and precipitated silica described in some in vitro studies with murine macrophages at exaggerated exposure levels seem to be related to interactions with cell culture proteins and cell membranes. The in vivo studies do not indicate that there is a toxicologically relevant difference between SAS products after oral exposure. It is noted that any silicon dioxide product not meeting established specifications, and/or produced to provide new functionality in food, requires its own specific safety and risk assessment.

Simple in vitro models can predict pulmonary toxicity of silver nanoparticles

To study the effects of nanomaterials after inhalation, a large number of in vitro lung models have been reported in literature. Although the in vitro models contribute to the reduction of animal studies, insufficient data exists to determine the predictive value of these in vitro models for the in vivo situation. The aim of this study was to determine the correlation between in vitro and in vivo data by comparing the dose metrics of silver nanoparticles in an in vitro lung model of increasing complexity to our previously published in vivo inhalation study. In vivo, the previously published study showed that the alveolar dose expressed as particle surface area is the most suitable dose metric to describe the toxicity of silver nanoparticles after inhalation. The results of the present study show that particle surface area is a suitable dose metric to describe the effects of silver nanoparticles when using a simple monolayer of lung epithelial cells. The dose metric shifted from particle surface area to particle mass when adding an increasing number of macrophages. In addition, a co-culture of endothelial cells, epithelial cells and macrophages on a Transwell® insert correlated less well to the in vivo results compared to the epithelial monolayer. We conclude that for studying the acute pulmonary toxicity of nanoparticles simple in vitro models using an epithelial monolayer better predict the in vivo response compared to complex co-culture models.

A novel nano-sized binuclear nickel(ii) Schiff base complex as a precursor for NiO nanoparticles: synthesis, characterization, DFT study and antibacterial activity

We prepared a new nano-hexadentate Schiff base and its nickel(ii) complex using an ultrasonic method, which produced NiO with an average size of 53 nm.

Nanomaterials for Engineering Stem Cell Responses

Recent progress in nanotechnology has stimulated the development of multifunctional biomaterials for tissue engineering applications. Synergistic interactions between nanomaterials and stem cell engineering offer numerous possibilities to address some of the daunting challenges in regenerative medicine, such as controlling trigger differentiation, immune reactions, limited supply of stem cells, and engineering complex tissue structures. Specifically, the interactions between stem cells and their microenvironment play key roles in controlling stem cell fate, which underlines therapeutic success. However, the interactions between nanomaterials and stem cells are not well understood, and the effects of the nanomaterials shape, surface morphology, and chemical functionality on cellular processes need critical evaluation. In this Review, focus is put on recent development in nanomaterial-stem cell interactions, with specific emphasis on their application in regenerative medicine. Further, the emerging technologies based on nanomaterials developed over the past decade for stem cell engineering are reviewed, as well as the potential applications of these nanomaterials in tissue regeneration, stem cell isolation, and drug/gene delivery. It is anticipated that the enhanced understanding of nanomaterial-stem cell interactions will facilitate improved biomaterial design for a range of biomedical and biotechnological applications.

Morphological observation of embryoid bodies completes the in vitro evaluation of nanomaterial embryotoxicity in the embryonic stem cell test (EST)

The wide and frequent use of engineered nanomaterials (NMs) raises serious concerns about their safety for human health. Our aim is to evaluate the embryotoxic potential of silver, uncoated and coated zinc oxide, titanium dioxide and silica NMs through the embryonic stem cell test (EST). EST is a validated in vitro assay that permits classification of chemicals into three classes (non, weakly or strongly embryotoxic). Because of the peculiar physico-chemical characteristics of NMs, we first adapted and simplified the differentiation protocol. To verify the efficiency of this adapted protocol we screened 3 well-characterized chemicals (5-fluorouracil, hydroxyurea and saccharin). Next, we assessed the embryotoxic potential of NMs. Our data showed that silver NM is classified as a strong embryotoxic compound, while coated and uncoated zinc oxide, titanium and silica NMs as weak embryotoxic compounds. In addition, we observed daily the formation and growth of embryoid bodies (EBs). We showed that multiple EBs formed in each well starting from 50 μg/ml of SiO2 while EB formation was inhibited starting from 20 μg/ml of ZnO NMs. This has never been reported with chemicals and could pose a risk of wrongly evaluating the NMs embryotoxic potential. For NMs, morphological observation of EBs can provide valuable information on early differentiation effects. Finally, we suggest that the prediction model should be revised for the assessment of NMs embryotoxicity.

Comprehensive In Vitro Toxicity Testing of a Panel of Representative Oxide Nanomaterials: First Steps towards an Intelligent Testing Strategy

Nanomaterials (NMs) display many unique and useful physico-chemical properties. However, reliable approaches are needed for risk assessment of NMs. The present study was performed in the FP7-MARINA project, with the objective to identify and evaluate in vitro test methods for toxicity assessment in order to facilitate the development of an intelligent testing strategy (ITS). Six representative oxide NMs provided by the EC-JRC Nanomaterials Repository were tested in nine laboratories. The in vitro toxicity of NMs was evaluated in 12 cellular models representing 6 different target organs/systems (immune system, respiratory system, gastrointestinal system, reproductive organs, kidney and embryonic tissues). The toxicity assessment was conducted using 10 different assays for cytotoxicity, embryotoxicity, epithelial integrity, cytokine secretion and oxidative stress. Thorough physico-chemical characterization was performed for all tested NMs. Commercially relevant NMs with different physico-chemical properties were selected: two TiO₂ NMs with different surface chemistry – hydrophilic (NM-103) and hydrophobic (NM-104), two forms of ZnO – uncoated (NM-110) and coated with triethoxycapryl silane (NM-111) and two SiO₂ NMs produced by two different manufacturing techniques – precipitated (NM-200) and pyrogenic (NM-203). Cell specific toxicity effects of all NMs were observed; macrophages were the most sensitive cell type after short-term exposures (24-72h) (ZnO>SiO₂>TiO₂). Longer term exposure (7 to 21 days) significantly affected the cell barrier integrity in the presence of ZnO, but not TiO₂ and SiO₂, while the embryonic stem cell test (EST) classified the TiO₂ NMs as potentially ‘weak-embryotoxic’ and ZnO and SiO₂ NMs as ‘non-embryotoxic’. A hazard ranking could be established for the representative NMs tested (ZnO NM-110 > ZnO NM-111 > SiO₂ NM-203 > SiO₂ NM-200 > TiO₂ NM-104 > TiO₂ NM-103). This ranking was different in the case of embryonic tissues, for which TiO₂ displayed higher toxicity compared with ZnO and SiO₂. Importantly, the in vitro methodology applied could identify cell- and NM-specific responses, with a low variability observed between different test assays. Overall, this testing approach, based on a battery of cellular systems and test assays, complemented by an exhaustive physico-chemical characterization of NMs, could be deployed for the development of an ITS suitable for risk assessment of NMs. This study also provides a rich source of data for modeling of NM effects.

Silica-based matrices: State of the art and new perspectives for therapeutic drug delivery

Colloidal carriers based on silica (Si) matrices are an innovative approach within the context of therapeutic drug delivery systems. These carriers are emerging as a great promise for diagnosis and treatment of a wide range of injuries, particularly in cancer and infectious diseases. In addition, bioencapsulation for biosensing and cell therapy in silica sol-gel allows the survival of enzymes and cells for a long period of time. Owing to their porosity, large surface area, and high capability of functionalization, silica nanoparticles (SiNP) have been considered as an attractive option for several bioanalysis applications, such as selective bioseparation, imaging, and drug and gene delivery. However, although great advances are achieved in the biomedical fields, some toxicity effects can be associated with the use of SiNP. This article aims to present a comprehensive review of recent technological advances for silica matrices in biomedical applications, as well as the potential impact of silica-based materials on human health and environment.