ROS TRENDS in BiotechnologyFigure 3. Schematic representation of toxicology effect of multifunctional nanoparticles (NPs) in bacterial biofilms. Monodisperse superparamagnetic iron oxide NPs (SPIONs; black spheres) are coated with silver (gray shell), gold (yellow shell), and silver ring-coated, gold-coated SPIONs; silver ring-coated SPIONs and silver ring-coated, gold-coated SPIONs have strong toxic effects on bacterial biofilms, by penetration into the biofilms. Both SPIONs cores and the intermediate gold shell have the capability to induce heat by applying alternative magnetic and laser fields, respectively; the produced heat can be used as additional means to escalate bacterial death using these NPs. The magnified section in the center illustrates the irreversible effects of NPs and their ions on the various parts of the bacteria. § DOI of original article: http://dx

Nanomaterials offer opportunities to construct novel compounds for many different fields. Applications include devices for energy, including solar cells, batteries, and fuel cells, and for health, including contrast agents and mediators for photodynamic therapy and hyperthermia. Despite these promising applications, any new class of materials also bears a potential risk for human health and the environment. The advantages and innovations of these materials must be thoroughly compared against risks to evaluate each new nanomaterial. Although nanomaterials are often used intentionally, they can also be released unintentionally either inside the human body, through wearing of a prosthesis or the inhalation of fumes, or into the environment, through mechanical wear or chemical powder waste. This possibility adds to the importance of understanding potential risks from these materials. Because of fundamental differences in nanomaterials, sound risk assessment currently requires that researchers perform toxicology studies on each new nanomaterial. However, if toxicity could be correlated to the basic physicochemical properties of nanomaterials, those relationships could allow researchers to predict potential risks and design nanomaterials with minimum toxicity. In this Account we describe the physicochemical properties of nanoparticles (NPs) and how they can be determined and discuss their general importance for cytotoxicity. For simplicity, we focus primarily on in vitro toxicology that examines the interaction of living cells with engineered colloidal NPs with an inorganic core. Serious risk assessment of NPs will require additional in vivo studies. Basic physicochemical properties of nanoparticulate materials include colloidal stability, purity, inertness, size, shape, charge, and their ability to adsorb environmental compounds such as proteins. Unfortunately, the correlation of these properties with toxicity is not straightforward. First, for NPs released either unintentionally or intentionally, it can be difficult to pinpoint these properties in the materials. Therefore, researchers typically use NP models with better defined properties, which don't include the full complexity of most industrially relevant materials. In addition, many of these properties are strongly mutually connected. Therefore, it can be difficult to vary individual properties in NP models while keeping the others constant.

Inorganic nanoparticles are frequently engineered with an organic surface coating to improve their physicochemical properties, and it is well known that their colloidal properties may change upon internalization by cells. While the stability of such nanoparticles is typically assayed in simple in vitro tests, their stability in a mammalian organism remains unknown. Here, we show that firmly grafted polymer shells around gold nanoparticles may degrade when injected into rats. We synthesized monodisperse radioactively labelled gold nanoparticles ((198)Au) and engineered an (111)In-labelled polymer shell around them. Upon intravenous injection into rats, quantitative biodistribution analyses performed independently for (198)Au and (111)In showed partial removal of the polymer shell in vivo. While (198)Au accumulates mostly in the liver, part of the (111)In shows a non-particulate biodistribution similar to intravenous injection of chelated (111)In. Further in vitro studies suggest that degradation of the polymer shell is caused by proteolytic enzymes in the liver. Our results show that even nanoparticles with high colloidal stability can change their physicochemical properties in vivo.

are proving to be an emergent technology with potentially very attractive properties. They are potentially low cost and environmentally friendly with reduced supply risk. However, the development of NIBs faces various challenges such as low gravimetric and volumetric energy densities and difficulty in achieving broader voltage windows. Although early studies in NIBs date back to the 1970s, just like Li-ion battery (LIB) research, the commercialization of the former systems in 1991 by the team formed by Sony and Asahi Kasei marked a milestone not only in the field of energy storage technology but also in the evolution of the modern society. This technological breakthrough had been possible thanks to several preceding contributions, particularly the works by M. S Whittingham, [1] J. Goodenough, [2,3] and A. Yoshino [4] on the discovery of Li-ion intercalation materials (Nobel Laureates in Chemistry 2019). This important historical event polarized material science research toward Li-ion technology and slowed down considerably the advances in the field of sodium. However, at the end of the 2000s, mainly driven by the concerns about future lithium supply and the uneven worldwide distribution of its reserves and resources, the research on Na-ion reemerged and so did the number of articles published (Figure 1). The intercalation chemistry of both metal ions is very alike, and thus, the materials tested for NIBs could be similar to those used in Li-ion systems. Both systems share the same working principle, and therefore, in terms of manufacturing, the industry producing LIBs can be easily tuned towards NIB fabrication, which is an important asset to invest in and support this technology. NIBs started to reach the market in the early 2010s, about two decades after their Li counterparts. Nevertheless, the progress has been relatively fast due to the straightforward LIB equipment and facility transfer just mentioned. In the search of high performance, low cost, abundance, low environmental impact, long-term cyclability and safety, layered metal oxides, polyanionic compounds and Prussian blue analogues (PBAs) are among the most studied families of Na-ion cathode materials. On the anode side, metallic sodium exhibits the same operation and safety problems as lithium, and therefore, it cannot be considered an option in conventional NIBs. Thus, in this scenario, most of the research has been dominated by the use of disordered carbons, mainly hard carbons (HCs). Other prospective anodes

Sodium-oxygen batteries currently stimulate extensive research due to their high theoretical energy density and improved operational stability when compared to lithium-oxygen batteries. Cell stability, however, needs to be demonstrated also under resting conditions before future implementation of these batteries. In this work we analyze the effect of resting periods on the stability of the sodium superoxide (NaO2) discharge product. The instability of NaO2 in the cell environment is demonstrated leading to the evolution of oxygen during the resting period and the decrease of the cell efficiency. In addition, migration of the superoxide anion (O2(-)) in the electrolyte is observed and demonstrated to be an important factor affecting Coulombic efficiency.