Nanotechnology is the understanding and control of matter at nanoscale dimensions between approximately 1 and 100 nm, where unique phenomena enable novel applications.
Nanotoxicology can be defined as the study of adverse effects of nanomaterials on living organisms and the environment.
Surface properties are major determinants of biologic reactivity due to high surface area, surface charge, dissolution and release of metal ions, and redox activity leading to generation of ROS.
The respiratory tract is the major route for humans to exposure of nanomaterials.
Surface properties are major determinants of biologic reactivity due to high surface area, surface charge, hydrophobicity and partitioning into lipid membranes, dissolution and release of metal ions, and redox activity.
Dosemetric defines a dose in terms of an inherent property (physical, chemical, reactivity, etc.).
Nanotechnology has become a multibillion dollar industry worldwide, producing high volume, commercial nanomaterials including nanosilver, fullerenes, quantum dots, carbon nanotubes (CNTs), and metal oxide nanoparticles (NPs) (Figure 28–1). Nanotoxicology seeks to identify and characterize the hazards of engineered nanomaterials (ENMs) for purposes of risk assessment for humans and the environment, which requires a highly multidisciplinary team approach covering expertise in toxicology, biology, chemistry, physics, material science, geology, exposure assessment, physiologic-based pharmacokinetics (PBPK), and medicine. All these disciplines are necessary to develop testing strategies, establish toxicity ranking, determine “safe” exposure levels, and derive preventative exposure guidelines.
Length scales for natural and synthetic structures (above) and some examples of engineered nanomaterials of varying size and shape (below).
Perspectives: Engineered Nanoparticles versus Ambient Particulate Matter
Airborne ambient particulate matter (PM) can elicit adverse effects in the respiratory tract, in secondary organs and systemically (see Chapter 29). The smallest fraction of PM, referred to as ultrafine particulates (UFPs, <100 nm), has been associated with effects in the cardiovascular and central nervous system (CNS) as a consequence of their translocation to and distribution via blood circulation and neurons. Natural sources of ultrafine and nanoparticles include gas to particle conversions, forest fires, volcano eruptions, viruses, magnetotactic bacteria, mollusks, arthropods, fish and birds. Unintentional anthropogenic sources include internal combustion engines, power plants, metal fumes from smelting and welding and heated surfaces. Engineered nanoparticles would represent intentional sources. Epidemiologic studies have demonstrated that increased susceptibility to adverse effects from ambient particulate air pollution includes preexisting disease (asthma, diabetes), age (very young, elderly), or genetic background (polymorphism).
Properties and Behaviors of ENPs versus Larger Particles
Table 28–1 contrasts differences between NPs (<100 nm) and larger particles (>500 nm) in general characteristics, translocation propensity, and cellular effects assuming inhalational exposure. Biologic systems do not perceive a precise boundary at the 100 nm size threshold, but rather a gradual transition between nano- and larger-sized particles.