Water-soluble germanium nanoparticles cause necrotic cell death and the damage can be attenuated by blocking the transduction of necrotic signaling pathway

Nonlinear effects in optical trapping of titanium dioxide and diamond nanoparticles

Optical trapping in biophysics typically uses micron-scale beads made of materials like polystyrene or glass to probe the target of interest. Using smaller beads made of higher-index materials could increase the time resolution of these measurements. We characterized the trapping of nanoscale beads made of diamond and titanium dioxide (TiO2) in a single-beam gradient trap. Calculating theoretical expectations for the trapping stiffness of these beads, we found good agreement with measured values. Trap stiffness was significantly higher for TiO2 beads, owing to notable enhancement from nonlinear optical effects, not previously observed for continuous-wave trapping. Trap stiffness was over 6-fold higher for TiO2 beads than polystyrene beads of similar size at 70 mW laser power. These results suggest that diamond and TiO2 nanobeads can be used to improve time resolution in optical tweezers measurements.

Recent Advances in Nanomaterials of Group XIV Elements of Periodic Table in Breast Cancer Treatment

Breast cancer is one of the most common malignancies and a leading cause of cancer-related mortality among women worldwide. The elements of group XIV in the periodic table exhibit a wide range of chemical manners. Recently, there have been remarkable developments in the field of nanobiomedical research, especially in the application of engineered nanomaterials in biomedical applications. In this review, we concentrate on the recent investigations on the antiproliferative effects of nanomaterials of the elements of group XIV in the periodic table on breast cancer cells. In this review, the data available on nanomaterials of group XIV for breast cancer treatment has been documented, providing a useful insight into tumor biology and nano-bio interactions to develop more effective nanotherapeutics for cancer patients.

Mechanisms and pathogenesis underlying environmental chemical-induced necroptosis

Necroptosis is a regulated cell death that is governed by mixed lineage kinase domain-like, receptor-interacting serine-threonine kinase 3 and commonly displays with necrosis morphological characteristics. This study examined the molecular mechanisms involved in the chemical-induced necroptosis where a systematic evaluation of experimental studies addressing this issue is missing. We strictly reviewed all scientific reports related to our search terms including "necroptosis" or "programmed necrosis", "environmental chemicals" or "air pollutants" or "pesticides" or "nanoparticles" and "Medicines" from 2009 to 2019. Manuscripts that met the objective of this study were included for further evaluations. Studies showed that several pathological contexts like cancer, neurodegenerative disorders, and inflammatory diseases were related to necroptosis. Furthermore, multiple chemical-induced cytotoxic effects, such as DNA damage, mitochondrial dysregulation, oxidative damage, lipid peroxidation, endoplasmic reticulum disruption, and inflammation are also associated with necroptosis. The main environmental exposures that are related to necroptosis are air pollutants (airborne particulate matter, cadmium, and hydrogen sulfide), nanoparticles (gold, silver, and silica), pesticides (endosulfan, cypermethrin, chlorpyrifos, and paraquat), and tobacco smoke. To sum up, air pollutants, pesticides, and nanoparticles could potentially affect human health via disruption of cell growth and induction of necroptosis. Understanding the exact molecular pathogenesis of these environmental chemicals needs further comprehensive research to provide innovative concepts for the prevention approaches and introduce novel targets for the amelioration of a range of human health problems.

Targeting non-apoptotic cell death in cancer treatment by nanomaterials: Recent advances and future outlook

Many tumors develop resistance to most of the apoptosis-based cancer therapies. In this sense targeting non-apoptotic forms of cell death including necroptosis, autophagy and ferroptosis may have therapeutic benefits in apoptosis-defective cancer cells. Nanomaterials have shown great advantages in cancer treatment owing to their unique characteristics. Besides, the capability of nanomaterials to induce different forms of cell death has gained widespread attention in cancer treatment. Reports in this field reflect the therapeutic potential of necroptotic cell death induced by nanomaterials in cancer. Also, autophagic cell death induced by nanomaterials alone and as a part of chemo-, radio- and photothermal therapy holds great promise as anticancer therapeutic option. Besides, ferroptosis induction by iron-based nanomaterials in drug delivery, immunotherapy, hyperthermia and imaging systems shows promising results in malignancies. Hence, this review is devoted to the latest efforts and the challenges in this field of research and its clinical merits.

Effects of physical properties of nano-sized hydroxyapatite crystals on cellular toxicity in renal epithelial cells

Hydroxyapatite (HAP) is not only a common component of most idiopathic CaOx stones, but also the core of Randall's plaque. HAP is a nest that can induce the formation of Randall's plaques and even kidney stones. We studied the toxic effects and mechanisms of four different types of nano-HAP crystals (H-Sphere, 72.5 nm × 72.5 nm; H-Needle, 37.2 nm × 162.7 nm; H-Rod, 42.3 nm × 115.3 nm; and H-Plate, 145.5 nm × 272.9 nm) on human renal proximal tubular epithelial cells (HK-2). HAP crystals could cause oxidative stress that triggered a series of cell dysfunction problems, resulting in decreased cell viability, loss of cell membrane integrity, cell swelling, and cell necrosis. The toxic effect of HAP was mainly attributed to its entry into cell by endocytosis and its accumulation in the lysosomes, causing the level of intracellular reactive oxygen species (ROS) to rise, the mitochondrial membrane potential (Δψm) to decrease, the lysosomal integrity to be destroyed, and the cell cycle blocked during the G0/G1 phase. The cytotoxicity of the four kinds of HAP crystals was ranked as follows: H-Sphere > H-Needle > H-Rod > H-Plate. The cytotoxicity of each crystal was positively correlated with low absolute zeta potential, conduciveness to internalized morphology, large specific surface area and aspect ratio, and small particle size. These results indicated that nano-HAP could damage HK-2 cells, and the physical properties of HAP crystals play a vital effect in their cytotoxicity.

Defect-related luminescent bur-like hydroxyapatite microspheres induced apoptosis of MC3T3-E1 cells by lysosomal and mitochondrial pathways

When orthopedic joints coated by hydroxyapatite (HA) were implanted in the human body, they release wear debris into the surrounding tissues. The generation and accumulation of wear particles will induce aseptic loosening. However, the potential bioeffect and mechanism of HA-coated orthopedic implants on bone cells are poorly understood. In this study, defect-related luminescent bur-like hydroxyapatite (BHA) microspheres with the average diameter of 7-9 μm which are comparable to that of the wear-debris particles from aseptically loosened HA implants or HA debris have been synthesized by hydrothermal synthesis and the MC3T3-E1 cells were set as a cells model to study the potential bioeffect and mechanism of BHA microspheres. The studies demonstrated that BHA microspheres could be taken into MC3T3-E1 cells via endocytosis involved in micropinocytosis- and clathrin-mediated endocytosis process, and exert cytotoxicity effect. BHA microspheres could induce the cell apoptosis by intracellular production of reactive oxygen species (ROS), which led to not only an increase in the permeability of lysosome and release of cathepsins B, but also mitochondrial dysfunction and DNA damage. Our results provide novel evidence to elucidate their toxicity mechanisms and might be helpful for more reasonable applications of HA-based orthopaedic implants in the future.

Oxidative stress-induced apoptosis of osteoblastic MC3T3-E1 cells by hydroxyapatite nanoparticles through lysosomal and mitochondrial pathways

Hydroxyapatite nanoparticles (HAPs) cause apoptosis of osteoblastic MC3T3-E1 cells through oxidative stress-induced lysosomal and mitochondrial pathway.

In one harness: the interplay of cellular responses and subsequent cell fate after quantum dot uptake

Rapid growth and expansion of engineered nanomaterials will occur when the technology can be used safely. Quantum dots have excellent prospects in clinical applications, but the issue of toxicity has not yet been resolved. To enable their medical implementation, the effect on, and mechanisms in, live cells should be clearly known and predicted. A massive amount of experimental data dedicated to nanotoxicity has been accumulated to-date, but it lacks a logical structure. The current challenge is to organize existing knowledge into lucid biological and mathematical models. In our review we aim to describe the interplay of various cell death mechanisms triggered by quantum dots as a consequence of particle parameters and experimental conditions.

Exploiting the biological windows: current perspectives on fluorescent bioprobes emitting above 1000 nm

With the goal of developing more accurate, efficient, non-invasive and fast diagnostic tools, the use of near-infrared (NIR) light in the range of the second and third biological windows (NIR-II: 1000-1350 nm, NIR-III: 1550-1870 nm) is growing remarkably as it provides the advantages of deeper penetration depth into biological tissues, better image contrast, reduced phototoxicity and photobleaching. Consequently, NIR-based bioimaging has become a quickly emerging field and manifold new NIR-emitting bioprobes have been reported. Classes of materials suggested as potential probes for NIR-to-NIR bioimaging (using NIR light for the excitation and emission) are quite diverse. These include rare-earth based nanoparticles, Group-IV nanostructures (single-walled carbon nanotubes, carbon nanoparticles and more recently Si- or Ge-based nanostructures) as well as Ag, In and Pb chalcogenide quantum dots. This review summarizes and discusses current trends, material merits, and latest developments in NIR-to-NIR bioimaging taking advantage of the region above 1000 nm (i.e. the second and third biological windows). Further consideration will be given to upcoming probe materials emitting in the NIR-I region (700-950 nm), thus do not possess emissions in these two windows, but have high expectations. Overall, the focus is placed on recent discussions concerning the optimal choice of excitation and emission wavelengths for deep-tissue high-resolution optical bioimaging and on fluorescent bioprobes that have successfully been implemented in in vitro and in vivo applications.

Facile Synthesis of pH-sensitive Germanium Nanocrystals with High Quantum Yield for Intracellular Acidic Compartment Imaging

A green-light emitting germanium nanocrystal-based biosensor to monitor lysosomal pH changes is developed. The Ge nanocrystals are synthesized in an aqueous solution with a significantly enhanced photoluminescence quantum yield of 26%. This synthesis involves a facile solution based route which avoided the use of toxic or environmentally unfriendly agents. Importantly, the photoluminescence intensity of the synthesized Ge nanocrystals is particularly sensitive to changes in pH between 5 and 6. When incubated with cultured cells, the nanocrystals are internalized and subsequently translocated via the lysosomal pathway, and the Ge nanocrystals' fluorescence are greatly enhanced, even when the lysosomal pH is only slightly increased. These results reveal that the Ge nanocrystals possess high pH sensitivity compared to a commercially available dye, LysoSensor Green DND-189. The fluorescent properties of the Ge nanocrystals are demonstrated to be dependent on both the crystal form and their surface chemistry. The superior fluorescence properties and bioapplicability of the Ge nanocrystals makes them a promising intracellular bioimaging probe for monitoring various pH-sensitive processes in cells.

Europium-doped Gd2O3 nanotubes cause the necrosis of primary mouse bone marrow stromal cells through lysosome and mitochondrion damage

With the wide applications of europium-doped Gd2O3 nanoparticles (Gd2O3:Eu(3+) NPs) in biomedical fields, it will inevitably increase the chance of human exposure. It was reported that Gd2O3:Eu(3+) NPs could accumulate in bone. However, there have been few reports about the potential effect of Gd2O3:Eu(3+) NPs on bone marrow stromal cells (BMSCs). In this study, the Gd2O3:Eu(3+) nanotubes were prepared and characterized by powder X-ray diffraction (XRD), photoluminescence (PL) excitation and emission spectra, scanning electron microscope (SEM), and transmission electron microscopy (TEM). The cytotoxicity of Gd2O3:Eu(3+) nanotubes on BMSCs and the associated mechanisms were further studied. The results indicated that they could be uptaken into BMSCs by an energy-dependent and macropinocytosis-mediated endocytosis process, and primarily localized in lysosome. Gd2O3:Eu(3+) nanotubes effectively inhibited the viability of BMSCs in concentration and time-dependent manners. A significant increase in the percentage of late apoptotic/necrotic cells, lactate dehydrogenase (LDH) leakage and the number of PI-stained cells was found after BMSCs were treated by 10, 20, and 40μg/mL of Gd2O3:Eu(3+) nanotubes for 12h. No obvious DNA ladders were detected, but a dispersed band was observed. The above results revealed that Gd2O3:Eu(3+) nanotubes could trigger cell death by necrosis instead of apoptosis. Two mechanisms were involved in Gd2O3:Eu(3+) nanotube-induced BMSCs necrosis: lysosomal rupture and release of cathepsins B; and the overproduction of reactive oxygen species (ROS) injury to the mitochondria and DNA. The study provides novel evidence to elucidate the toxicity mechanisms and may be beneficial to more rational applications of these nanomaterials in the future.

Promoting cell proliferation using water dispersible germanium nanowires

Group IV Nanowires have strong potential for several biomedical applications. However, to date their use remains limited because many are synthesised using heavy metal seeds and functionalised using organic ligands to make the materials water dispersible. This can result in unpredicted toxic side effects for mammalian cells cultured on the wires. Here, we describe an approach to make seedless and ligand free Germanium nanowires water dispersible using glutamic acid, a natural occurring amino acid that alleviates the environmental and health hazards associated with traditional functionalisation materials. We analysed the treated material extensively using Transmission electron microscopy (TEM), High resolution-TEM, and scanning electron microscope (SEM). Using a series of state of the art biochemical and morphological assays, together with a series of complimentary and synergistic cellular and molecular approaches, we show that the water dispersible germanium nanowires are non-toxic and are biocompatible. We monitored the behaviour of the cells growing on the treated germanium nanowires using a real time impedance based platform (xCELLigence) which revealed that the treated germanium nanowires promote cell adhesion and cell proliferation which we believe is as a result of the presence of an etched surface giving rise to a collagen like structure and an oxide layer. Furthermore this study is the first to evaluate the associated effect of Germanium nanowires on mammalian cells. Our studies highlight the potential use of water dispersible Germanium Nanowires in biological platforms that encourage anchorage-dependent cell growth.

Programmed cell death: molecular mechanisms and implications for safety assessment of nanomaterials

Engineered nanomaterials offer numerous and tantalizing opportunities in many sectors of society, including medicine. Needless to say, attention should also be paid to the potential for unexpected hazardous effects of these novel materials. To date, much of the nanotoxicology literature has focused on the assessment of cell viability or cell death using primitive assays for the detection of plasma membrane integrity or mitochondrial function or assessment of cellular morphology. However, when assessing the cytotoxic effects of engineered nanomaterials, researchers need not only to consider whether cells are dead or alive but also to assess which of the numerous, highly specific pathways of cell death might be involved. Moreover, it is important to diagnose cell death based not only on morphological markers but on the assessment and quantification of biochemical alterations specific to each form of cell death. In this Account, we provide a description of the three major forms of programmed cell death in mammalian cells: apoptosis, autophagic cell death, and regulated necrosis, sometimes referred to as necroptosis. Apoptosis can be activated via the extrinsic (death receptor-dependent) or via the intrinsic (mitochondria-dependent) route. Apoptotic cell death may or may not require the activation of cytosolic proteases known as caspases. Autophagy (self-eating) has an important homeostatic role in the cell, mediating the removal of dysfunctional or damaged organelles thereby allowing the recycling of cellular building blocks. However, unrestrained autophagy can kill cells. Studies in recent years have revealed that necrosis that depends on activation of the kinases RIP1 and RIP3 is a major form of programmed cell death with roles in development and immunity. We also discuss recent examples of the impact of engineered nanoparticles on the three different pathways of programmed cell death. For example, acute exposure of cells to carbon nanotubes (CNTs) can induce apoptosis whereas chronic exposure to CNTs may yield an apoptosis-resistant and tumorigenic phenotype in lung epithelial cells. Several reports show that nanoparticles, including polystyrene particles, are routed to the lysosomal compartment and trigger cell death through the destabilization of lysosomal membranes with engagement of the intrinsic apoptosis pathway. In addition, a number of studies have demonstrated that nanomaterials such as CNTs, quantum dots, and gold nanoparticles can affect cellular autophagy. An improved understanding of the complexities of the nanomaterial-induced perturbation of different cell death pathways may allow for a better prediction of the consequences of human exposure.

Nanomaterials toxicity and cell death modalities

In the last decade, the nanotechnology advancement has developed a plethora of novel and intriguing nanomaterial application in many sectors, including research and medicine. However, many risks have been highlighted in their use, particularly related to their unexpected toxicity in vitro and in vivo experimental models. This paper proposes an overview concerning the cell death modalities induced by the major nanomaterials.