Nano LIFE

It is well documented that various particulate matter — either incidental or engineered — are known to generate reactive oxygen species (ROS) in living cells. In circumstances where these reactive species are generated, antioxidant production is often increased. This balance in the biological reduction/oxidation (a.k.a. redox) state within the cell has not been thoroughly studied in exposures involving engineered nanoparticles. However, nanoparticle exposure has been postulated to induce a DNA damage cascade. In this study, we examined primary human dermal fibroblasts (HDF) exposed to three different, but commonly used engineered nanoparticles (i.e., cerium dioxide (CeO₂), titanium dioxide (TiO₂) and zinc oxide (ZnO)) in an attempt to determine the potential DNA damaging effects through the analysis of ROS generation, relevant protein upregulation response and single and double DNA strand breaks. Cell death was most elevated with exposure to ZnO, followed by TiO₂ and CeO₂. ROS generation was measured at 1 h, 6 h and 24 h after exposure to particles via a cell-based DCFH-DA (2′, 7′-dichlorfluorescein-diacetate) assay and indicated that ZnO generated the most significant amount of ROS. ZnO also caused upregulation of oxidative stress protein, heme oxygenase-1 and phosphorylation of p38; whereas CeO₂ caused upregulation of superoxide dismutase. Results from the comet assay indicated that ZnO triggered significant DNA damage in cells at relatively low dosing concentrations (20 ppm). Immunocytochemistry with ZnO-treated cells revealed notable DNA double strand breaks evidenced by a marked increase in the presence of γ-H2AX foci. This finding was also indicated by western blot, as well as cell cycle arrest by the phosphorylation of cyclin-dependent kinase 1. These data suggest that the three particle-types induce different degrees of DNA damage. And, of the three particle-types tested, exposure to ZnO nanoparticles may cause the most significant DNA damage.

Magnetic nanoparticles have received considerable attention in nanomedicine due to their potential application as therapeutic or diagnostic tools based on their particular properties. However, prior to clinical application investigating the effect of these nanoparticles on cells is essential. The aim of the following study is therefore to evaluate the cytotoxicity of magnetic (Fe₃O₄) and gold-coated magnetic nanoparticles (Fe₃O₄@Au) on various cell lines in order to clarify the risk of these materials for human use. Toxicity of these nanoparticles on human dermal fibroblasts (SKIN), human squamous cell carcinoma cells (A431 cells) and human epidermal keratinocytes (HaCaT cells) were determined using the MTT assay. Results showed that, within the used concentration range, Fe₃O₄ nanoparticles had no significant effect on all investigated cell lines, while Fe₃O₄@Au nanoparticles seem to have a moderate toxicity on all cell lines with some selectivity for the malignant cells, although it is yet moderate. The different characteristic of the cell lines' survival with respect to incubation time and nanoparticle concentration could be partly due to different cell death modes. Therefore, the prepared Fe₃O₄ nanoparticles are harmless and could be applied safely for skin cancer treatment or diagnosis.

Silver (Ag) and zinc oxide (ZnO) are well known for both antimicrobial and pro-healing properties. Here, we present a novel method to synthesize Ag and ZnO nanoparticles (NPs), as well as hybrid Ag/ZnO NPs using a custom, temperature controlled microwave assisted technique. Microwave synthesis has been shown not only to enhance the rate of chemical reactions, but also in some cases to give higher product yields over thermal heating. The as-synthesized NPs were characterized by X-ray diffraction (XRD) to study the crystalline structure, composition and purity. Transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS) was used to study particle size, shape, composition and morphology. These results indicated that the as-prepared Ag NPs are spherical in shape and ~ 20 nm in sizes. The ZnO NPs are typically rod shaped and the particle sizes are ~ 20 nm in width and 100 nm in length. These NPs were tested for antibacterial and/or antifungal properties using disc diffusion assays. Results show microwave synthesized NPs inhibit growth of S. aureus, E. coli and C. albicans at 50 μ g/mL treatment concentration. Ag NPs were most effective in inhibiting bacterial and fungal growth at the concentrations tested followed by hybrid Ag/ZnO and ZnO nanoparticles. These results also suggest that the hybridization of ZnO to Ag NPs may reduce the toxicity of Ag NPs. Further studies are needed to understand the functional interaction between the two types of NPs and to improve their ability for biological or biomedical application.

Nanotoxicology is a concern. While skin exposure is generally perceived as less hazardous than inhalation or ingestion of engineered nanoparticles, there remain significant knowledge gaps in the topic to suggest greater caution in making a conclusion. Penetration of nanoparticles across an intact skin barrier is low. However, the verdict is still out on how this will change in situations where the skin barrier is compromised. Many studies on the interaction of nanoparticles with biological systems including skin cells have been reported. Under different scenarios, nanoparticles commonly found in topical skin products have been shown to be capable of exerting a variety of toxicological influences. These influences include causing cell death, stress, inflammation and damage to DNA. While alarming, it should also be noted that there remains much confusion and contradiction in the literature due to the complexity of studying cell–nanoparticle interactions. This review aims to provide a concise perspective on our current understanding of nanotoxicology in the skin, and identify the knowledge gaps where research efforts may be focused to help clarify the uncertainties in the field.

With the aging of the population and a correlated increase in the incidence of osteoarticular damage, great attention is focused on regenerative nanomedicine solutions to restore durable articular function and comfort. A durable cartilage repair is not effective without regeneration of an intact subchondral bed along with the surface chondral regeneration. Our expected outcomes are the development of clinical applications in the field of tissue engineering and nanomedicine, and more particularly in bone-cartilage unit regeneration. Here we report for the first time the nanomechanical analysis of the retrieved active implant after subchondral bone regeneration in vivo, which is much more efficient and long lasting solution to osteochondral defects than the existing ones. We believe that our results make a significant contribution to the area of regenerative nanomedicine. The concepts discovered here may serve to design sophisticated implants for placement into a broad variety of tissues.

Stem cells offer a promising tool in tissue engineering strategies, as their differentiated derivatives can be used to reconstruct most biological tissues. These approaches rely on controlling the biophysical cues that tune the ultimate fate of cells. In this context, significant effort has gone to parse out the role of conflicting matrix-elicited signals (e.g., topography and elasticity) in regulation of macroscopic characteristics of cells (e.g., shape and polarity). A critical hurdle, however, lies in our inability to recapitulate the nanoscale spatiotemporal pattern of these signals. The study presented in this manuscript took an initial step to overcome this challenge by developing a carbon nanotube (CNT)-based substrate for nanoresolution control of focal adhesion formation and cell alignment. The utility of this system was studied using human umbilical vascular endothelial cells (HUVECs) and human embryonic stem cells (hESCs) at a single cell level. Our results demonstrated the ability to control cell orientation by merely controlling the alignment of focal adhesions at a nanoscale size. Our long-term vision is to use these nanoengineered substrates to mimic cell orientation in earlier development and explore the role of polarity in asymmetric division and lineage specification of dividing cells.