Abstract
While attending a recent toxicology meeting, I listened to a few young scientists refer to themselves as “nanotoxicologists” and smiled as my imagination momentarily pictured very tiny toxicologists that might, in a science fiction story, be injected into the vasculature of a human on a medical mission involving a toxic substance or that might have been accidentally shrunk by an eccentric scientist parent to better understand the effects of toxic substances in the environment. Of course, I knew they meant to convey their strong interest toward investigating the toxicology of nanomaterials and the myriad of new products that are enabled by nanotechnology.
Nanotoxicology is a subdiscipline of toxicology that has become well established over the past decade and is currently one of the most, if not the most, rapidly developing areas of toxicologic interest internationally. In fact, the origin of the term “nanotoxicology” itself was born out of the recognition by inhalation toxicologists that ultrafine particles and engineered nanoparticles, which have dimensions in the range of 1 to 100 nm could have significant toxicologic effects that differentiate them from being simply very small quantities of the chemicals present in their composition. Definitions of nanomaterials vary from the more formal definition of engineered nanotechnology that includes any structure having at least 1 dimension in the 1 to 100 nm range, to a more liberal range of substances with particulate dimensions of >1 nm up to <999 nm that has been proposed by some scientists and regulators. Whatever the precise definition of the nanomaterial, it is now appreciated that the size, shape, surface characteristics, including charge and other aspects of the physical nature of a nanomaterial, can profoundly alter its toxicologic effects. In the nanomaterial world, it has been clearly demonstrated that nanotoxicology involves, and must include, an understanding of the toxicologic characteristics of a nanomaterial on the basis of its combined chemical and physical characteristics, which interact to contribute and result in unique interactions with biologic systems.
Our interest and ability to understand and manipulate matter at the nanoscale had its basis with the quantum physics of the 1950s that led to a comprehensive understanding of the biologic role and significance of DNA and opened the door to a biomolecular revolution that never stopped developing. Then, in the 1990s, we advanced our ability to manipulate matter to the extent that the dreams of the nanostructures and nanomachines of 2 decades ago are now becoming reality.
Nanotoxicology is a fascinating and new world of exploration and discovery for the toxicologist, one that we only imagined a couple of decades ago to include fears by some that the emergence of nanotechnology might result in catastrophic toxicologic effects that could destroy our planet with toxic, self-propagating, nano “goo” or that we might be irresponsible with respect to recognizing the potential toxicity of nanomaterials and create highly lethal and environmentally refractory nanoproducts. Instead, toxicologists internationally have responded with great interest in understanding the toxic properties of the wide variety of emerging nanotechnology-derived products. The results of these efforts are leading to the establishment of safety assessment guidelines, classification schemes, testing and screening procedures, as well as the development of effective protective technologies so that we can safely work with even the most potentially hazardous nanomaterials.
Many of us remember a time when there were attempts to quantify the number of potential new molecular structures that might be included in a toxicologic substance inventory or have been concerned that molecular libraries used for pharmaceutical and industrial formulation discovery would reach a point with increasingly limited options for new therapeutics and commercial products. Instead, we now are crossing the threshold where we have the ability to both make and manipulate atoms to “engineer” essentially any reasonably stable molecular structure we desire, guided by genomic and proteomic opportunities to explore molecular biologic interactions that enable new product development frontiers such as therapeutics in molecular medicine and nanomedicine as well as in the use of engineered nanomaterials for environmental remediation.
Nanotoxicology and molecular toxicology are relatively new subdisciplines of toxicological science that have been enabled by the advancement and maturation of materials science, chemistry, and biochemistry over a several decades. Both of these developing and expanding new subdisciplines build on the foundational work by many scientists including physicists, chemists, engineers, physiologists, and toxicologists that explored and endeavored to define nanotechnology as a new concept of “small” that includes the need to understand the potential harm that nanoscale materials may pose to biologic systems. Nanotoxicology is indeed a very fascinating new area of toxicology. Now, we observe a growing number of young toxicologists excited and making new contributions to our understanding of this potential for adverse effects, further defining and expanding the foundational work of nanotoxicology. These efforts are leading to a more complete understanding of the world and universe to include and incorporate the toxicology of nanomaterials and nanostructures using a growing toolbox of new instruments and methods that include applications of quantum physics and molecular engineering that allow evaluations at the nanoscale of the biologic molecular and structural machinery that enables as well as adversely affects life.
This special edition of International Journal of Toxicology includes a few selected, different, and interesting examples of work showing how nanotechnology products are evaluated for toxicity and assessed for safety that we hope you will enjoy reading about. We also hope you will contribute some of your own work with nanomaterials as we continue to look forward to reading additional, informative articles involving safe nanomaterial development and safety assessment in future editions and volumes of the journal.