Filling Knowledge Gaps that Distinguish the Safety Profiles of Nano versus Bulk Materials

The nanotechnology revolution will lead to large scale production of engineered nanomaterials that will impact every aspect of our lives. The unique physicochemical properties and functions of engineered nanomaterials could also pose new biological hazards to humans and the environment, including exposure through inhalation, ingestion, skin uptake, or the therapeutic use of these materials in the workplace and consumer products. Thus, an understanding of the science that underpins the biological hazard of nanomaterials is important for the sustainable development of this technology. Research into the hazards of engineered nanomaterials has spawned the development of a new multidisciplinary science—nanotoxicology—which aims to understand the toxicological effects and environmental impacts of engineered nanomaterials when they are exposed to humans and the environment. A key question introduced by the advent of nanotoxicology is whether a consideration of the toxicological properties of nanomaterials requires a modification of traditional toxicological principles. For instance, the use of mass concentration to express the dose–response relationships for nanomaterials differs from exposure to bulk materials because the introduction of nanoscale properties, specific surface area, and particle number introduce novel dose metrics that need to be considered. Moreover, unlike traditional toxicology, the exposure dose may be modified by the aggregation and agglomeration of nanoparticles under exposure conditions or in biological environments. In addition to dose, other factors that are difficult to ascertain include exposure routes, specific nanoscale dimensions, the physicochemical properties and functionality, material surfaces, etc., all of which can dynamically change as a function of time. Moreover, major alterations of the physicochemical properties of nano as compared to bulk materials of the same chemical composition, and the emergence of new functions at nanoscale dimensions, will undoubtedly lead to different toxicological outcomes in vivo. So a part of the existing database of safety evaluation for bulk materials, including the effects on health and the environment, is probably no longer valid when extrapolating and applying it for the safety assessment of nanomaterials. Against this background, it is clear that important knowledge gaps need to be filled in nanotoxicology, which have not been actively pursued for about ten years. It is timely to summarize the previous findings and to obtain experts’ views on the future directions of nanotoxicology research. Accordingly, we have developed this special issue to appraise the reader of the latest progress in nanotoxicology. This includes a coverage of major topics such as, to mention a few, the toxicological/biological effects of nanomaterials; understanding the toxicological aspects of nanomedicines; the biological and chemical mechanisms of the toxicological/biological properties of nanomaterials and nanomedicines; analytical methods and techniques for characterizing the toxicological, biomedical, or environmental effects of nanomaterials; theoretical modeling of the structure–activity relationships leading to nanomaterial hazards, and; the safer design of nanomaterials in response to this knowledge acquisition. In addition to understanding the fundamental knowledge of interaction processes between nanoscale matter and biological systems, and between nanoscale materials and environmental systems, a significant goal of nanotoxicology research is to guarantee the development of healthy and sustainable nanoscience and nanotechnology. Use of the scientific principles that underpin the generation of hazards at the nano/bio interface is important for predicting, reducing, or eliminating the potential toxicity of nanomaterials. This special issue outlines the fundamental knowledge that is required for the safe implementation of nanotechnology for the benefit of society, the environment, and the global economy.