Standard Cellular Testing Conditions Generate an Exaggerated Nanoparticle Cytotoxicity Profile

Cell viability of fine powders in hybrid resins and ceramic materials for CAD/CAM

Resin blocks and ceramic blocks for CAD/CAM crowns were cut into powders and separated into three particle size groups. Oxidative stress and cell viability were measured in 3T3 and FRSK cells. The results of cytotoxicity tended to be slightly higher for resin than for ceramics. The values also increased as the particle size decreased in the powders. In addition, incorporation into cells was frequently observed under SEM, suggesting that the particle size of easily incorporated dust is different among cell types. Fluorescence-activated cell sorter (FACS) showed an increase in apoptosis and a decrease in cell viability in most of the sample groups compared to the control group. Hematoxylin and eosin staining of the cells showed deep staining of the nuclei in the sample groups. It was found that oxidative stress cell viability and apoptosis appeared differently depending on the size of the particles and the type of cells.

Toxicity of different types of quantum dots to mammalian cells in vitro: An update review

Currently, there are a great quantity type of quantum dots (QDs) that has been developed by researchers. Depending on the core material, they can be roughly divided into cadmium, silver, indium, carbon and silicon QDs. And studies on the toxicity of QDs are also increasing rapidly, but in vivo tests in model animals fail to reach a consistent conclusion. Therefore, we review the literatures dealing with the cytotoxicity of QDs in mammalian cells in vitro. After a short summary of the application characteristics of five types of QDs, the fate of QDs in cells will be discussed, ranging from the uptake, transportation, sublocation and excretion. A substantial part of the review will be focused on in vitro toxicity, in which the type of QDs is combined with their adverse effect and toxic mechanism. Because of their different luminescent properties, different subcellular fate, and different degree of cytotoxicity, we provide an overview on the balance of optical stability and biocompatibility of QDs and give a short outlook on future direction of cytotoxicology of QDs.

Autophagy Modulated by Inorganic Nanomaterials

With the rapid development of nanotechnology, inorganic nanomaterials (NMs) have been widely applied in modern society. As human exposure to inorganic NMs is inevitable, comprehensive assessment of the safety of inorganic NMs is required. It is well known that autophagy plays dual roles in cell survival and cell death. Moreover, inorganic NMs have been proven to induce autophagy perturbation in cells. Therefore, an in-depth understanding of inorganic NMs-modulated autophagy is required for the safety assessment of inorganic NMs. This review presents an overview of a set of inorganic NMs, consisting of iron oxide NMs, silver NMs, gold NMs, carbon-based NMs, silica NMs, quantum dots, rare earth oxide NMs, zinc oxide NMs, alumina NMs, and titanium dioxide NMs, as well as how each modulates autophagy. This review emphasizes the potential mechanisms underlying NMs-induced autophagy perturbation, as well as the role of autophagy perturbation in cell fate determination. Furthermore, we also briefly review the potential roles of inorganic NMs-modulated autophagy in diagnosis and treatment of disease.

Anisotropic nanomaterials for shape-dependent physicochemical and biomedical applications

This review contributes towards a systematic understanding of the mechanism of shape-dependent effects on nanoparticles (NPs) for elaborating and predicting their properties and applications based on the past two decades of research. Recently, the significance of shape-dependent physical chemistry and biomedicine has drawn ever increasing attention. While there has been a great deal of effort to utilize NPs with different morphologies in these fields, so far research studies are largely localized in particular materials, synthetic methods, or biomedical applications, and have ignored the interactional and interdependent relationships of these areas. This review is a comprehensive description of the NP shapes from theory, synthesis, property to application. We figure out the roles that shape plays in the properties of different kinds of nanomaterials together with physicochemical and biomedical applications. Through systematic elaboration of these shape-dependent impacts, better utilization of nanomaterials with diverse morphologies would be realized and definite strategies would be expected for breakthroughs in these fields. In addition, we have proposed some critical challenges and open problems that need to be addressed in nanotechnology.

An automatable platform for genotoxicity testing of nanomaterials based on the fluorometric γ-H2AX assay reveals no genotoxicity of properly surface-shielded cadmium-based quantum dots

The large number of nanomaterial-based applications emerging in the materials and life sciences and the foreseeable increasing use of these materials require methods that evaluate and characterize the toxic potential of these nanomaterials to keep safety risks to people and environment as low as possible. As nanomaterial toxicity is influenced by a variety of parameters like size, shape, chemical composition, and surface chemistry, high throughput screening (HTS) platforms are recommended for assessing cytotoxicity. Such platforms are not yet available for genotoxicity testing. Here, we present first results obtained for application-relevant nanomaterials using an automatable genotoxicity platform that relies on the quantification of the phosphorylated histone H2AX (γ-H2AX) for detecting DNA double strand breaks (DSBs) and the automated microscope system AKLIDES® for measuring integral fluorescence intensities at different excitation wavelengths. This platform is used to test the genotoxic potential of 30 nm-sized citrate-stabilized gold nanoparticles (Au-NPs) as well as micellar encapsulated iron oxide nanoparticles (FeOx-NPs) and different cadmium (Cd)-based semiconductor quantum dots (QDs), thereby also searching for positive and negative controls as reference materials. In addition, the influence of the QD shell composition on the genotoxic potential of these Cd-based QDs was studied, using CdSe cores as well as CdSe/CdS core/shell and CdSe/CdS/ZnS core/shell/shell QDs. Our results clearly revealed the genotoxicity of the Au-NPs and its absence in the FeOx-NPs. The genotoxicity of the Cd-QDs correlates with the shielding of their Cd-containing core, with the core/shell/shell architecture preventing genotoxicity risks. The fact that none of these nanomaterials showed cytotoxicity at the chosen particle concentrations in a conventional cell viability assay underlines the importance of genotoxicity studies to assess the hazardous potential of nanomaterials.

Unveiling the potentials of biocompatible silver nanoparticles on human lung carcinoma A549 cells and Helicobacter pylori

Silver nanoparticles (AgNPs) are gaining importance in health and environment. This study synthesized AgNPs using the bark extract of a plant, Toxicodendron vernicifluum (Tv) as confirmed by a absorption peak at 420 nm corresponding to the Plasmon resonance of AgNPs. The AgNPs were spherical, oval-shaped with size range of 2–40 nm as evident by field emission transmission electron microscopy (FE-TEM) and particle size analysis (PSA). The particles formed were crystalline by the presence of (111), (220) and (200) planes, as revealed by X ray diffraction (XRD) and energy dispersive spectroscopy (EDS). The presence of amine, amide, phenolic, and alcoholic aromatics derived from Tv extract was found to be capping and or reducing agents as evident by Fourier-transform infrared spectroscopy (FTIR) spectra. The Tv-AgNPs were observed to be biocompatible to chick embryonic and NIH3T3 cells at various concentrations. Interestingly, Tv-AgNPs at the concentration of 320 µg. mL⁻¹ induced 82.5% of cell death in human lung cancer, A549 cells and further 95% of cell death with annexin V FITC/PI based apoptosis. The Tv-AgNPs selectively targeted and damaged the cancer cells through ROS generation. The Tv-AgNPs displayed minimal inhibitory concentration (MIC) of 8.12 µg.mL⁻¹ and 18.14 µg.mL⁻¹ against STEC and H. pylori respectively. This multi-potent property of Tv-AgNPs was due to shape and size specific property that facilitated easy penetration into the bacterial and cancer cells for targeted therapy.

Genotoxicity of amorphous silica nanoparticles: Status and prospects

Amorphous silica nanoparticles (SNPs) are widely used in biomedical applications and consumer products. Little is known, however, about their genotoxicity and potential to induce gene expression regulation. Despite recent efforts to study the underlying mechanisms of genotoxicity of SNPs, inconsistent results create a challenge. A variety of factors determine particle-cell interactions and underlying mechanisms. Further, high-throughput studies are required to carefully assess the impact of silica nanoparticle physicochemical properties on induction of genotoxic response in different cell lines and animal models. In this article, we review the strategies available for evaluation of genotoxicity of nanoparticles (NPs), survey current status of silica nanoparticle gene alteration and genotoxicity, discuss particle-mediated inflammation as a contributing factor to genotoxicity, identify existing gaps and suggest future directions for this research.

Fe-Doped ZnO nanoparticle toxicity: assessment by a new generation of nanodescriptors

In the search for novel tools to combat cancer, nanoparticles (NPs) have attracted a lot of attention. Recently, the controlled release of cancer-cell-killing metal ions from doped NPs has shown promise, but fine tuning of dissolution kinetics is required to ensure specificity and minimize undesirable toxic side-effects. Theoretical tools to help in reaching a proper understanding and finally be able to control the dissolution kinetics by NP design have not been available until now. Here, we present a novel set of true nanodescriptors to analyze the charge distribution, the effect of doping and surface coating of whole metal oxide NP structures. The polarizable model of oxygen atoms enables light to be shed on the charge distribution on the NP surface, allowing the in detail study of the factors influencing the release of metal ions from NPs. The descriptors and their capabilities are demonstrated on a Fe-doped ZnO nanoparticle system, a system with practical outlook and available experimental data.

Biocompatible properties of nano-drug carriers using TiO2-Au embedded on multiwall carbon nanotubes for targeted drug delivery

Nanomaterial-based drug carriers have become a hot spot of research at the interface of nanotechnology and biomedicine because they allow efficient loading, targeted delivery, controlled release of drugs, and therefore are promising for biomedical applications. The current study made an attempt to decorate the multiwalled carbon nanotubes (MWCNT) with titanium dioxide‑gold nanoparticles in order to enhance the biocompatibility for doxorubicin (DOX) delivery. The successful synthesis of nano drug carrier (NDC) was confirmed by XRD, XPS and UV-Visible spectroscopy. FESEM and TEM revealed that the morphology of NDC can be controlled by manipulating the reaction duration, MWCNT concentration and TiO₂-Au source concentration. Results showed that TiO₂ and Au nanoparticles were well coated on MWCNT. NDC had finely tuned biocompatible properties, as elucidated by hemolytic and antimicrobial assays. NDC also showed a high antioxidant potential, 80.7% expressed as ascorbic acid equivalents. Commercial DOX drug was utilized to treat A549 and MCF7 cancer cell lines showing improved efficiency by formulating it with NDC, which selectively delivered at the pH 5.5 with drug loading capacity of 0.45 mg/mL. The drug releasing capacity achieved by NDC was 90.66% for 10 h, a performance that far encompasses a wide number of current literature reports.

Autophagy promotes degradation of polyethyleneimine-alginate nanoparticles in endothelial progenitor cells

Polyethyleneimine (PEI)–alginate (Alg) nanoparticle (NP) is a safe and effective vector for delivery of siRNA or DNA. Recent studies suggest that autophagy is related to cytotoxicity of PEI NPs. However, contribution of autophagy to degradation of PEI–Alg NPs remains unknown. CD34⁺VEGFR-3⁺ endothelial progenitor cells isolated from rat bone marrow were treated with 25 kDa branched PEI modified by Alg. After treatment with the NPs, morphological changes and distribution of the NPs in the cells were examined with scanning and transmission electron microscopies. Cytotoxicity of the NPs was analyzed by reactive oxygen species (ROS) production, lactate dehydrogenase leakage and induction of apoptosis. The level of autophagy was assessed with expression of Beclin-1 and LC3 and formation of autophagic structures and amphisomes. Colocalization of LC3-positive puncta and the NPs was determined by LC3–GFP tracing. Cytotoxicity of PEI NPs was reduced greatly after modification with Alg. PEI–Alg NPs were distributed in mitochondria, rough endoplasmic reticula and nuclei as well as cytoplasm. After phagocytosis of the NPs, expression of Beclin-1 mRNA and LC3 protein was upregulated, and the number of LC3-positive puncta, autophagic structures and amphisomes increased significantly. The number of lysosomes also increased obviously. There were LC3-positive puncta in nuclei, and some puncta were colocalized with the NPs. These results demonstrate that the activated autophagy promotes degradation of PEI–Alg NPs via multiple pathways.

Colloidal Gold Nanoparticles Induce Changes in Cellular and Subcellular Morphology

Exposure of cells to colloidal nanoparticles (NPs) can have concentration-dependent harmful effects. Mostly, such effects are monitored with biochemical assays or probes from molecular biology, i.e., viability assays, gene expression profiles, etc., neglecting that the presence of NPs can also drastically affect cellular morphology. In the case of polymer-coated Au NPs, we demonstrate that upon NP internalization, cells undergo lysosomal swelling, alterations in mitochondrial morphology, disturbances in actin and tubulin cytoskeleton and associated signaling, and reduction of focal adhesion contact area and number of filopodia. Appropriate imaging and data treatment techniques allow for quantitative analyses of these concentration-dependent changes. Abnormalities in morphology occur at similar (or even lower) NP concentrations as the onset of reduced cellular viability. Cellular morphology is thus an important quantitative indicator to verify harmful effects of NPs to cells, without requiring biochemical assays, but relying on appropriate staining and imaging techniques.