MINIREVIEW
www.rsc.org/nanoscale | Nanoscale
Computational strategies for predicting the potential risks associated with nanotechnology Amanda S. Barnard* Received 19th April 2009, Accepted 29th June 2009 First published as an Advance Article on the web 13th August 2009 DOI: 10.1039/b9nr00154a For the move from nanoscience to nanotechnology to be sustainable, it is important that the issues surrounding possible ‘nano-hazards’ be addressed before commercialization. The global push for more environmentally friendly, biodegradable products, means the introduction of the nanoparticles contained within these products into the ecosystem is an inevitability. When this happens, it is desirable to know how the hazardous properties may be affected, and what the potential hazards are. In this article, a number of strategies will be discussed, combining the desirable aspects of theory, simulation, experiment and observation, and leading to predictions for incorporation into preventative frameworks. Particular attention will be given to the role of theory and computation, and how it intersects with the participants from complementary fields.
1. Introduction It is clear from the range of studies decorating the literary landscape that engineered nanoparticles present superior properties for a diverse range of industrial applications such as chemical sensing and fuel catalysis, and biomedical applications such as drug delivery and medical imaging. Nanoscience is starting to turn into nanotechnology, and development of a variety of anticipated applications, such as sensors1 (including biosensors2), bio-labels,3 tips for scanning probe microscopy,4 electrochemical actuators5 and batteries6 are now beginning to be realized. However, for this transition to be sustainable, scientists and engineers must navigate a delicate balance between technological advancement and social awareness.7 Commonwealth Scientific and Industrial Research Organisation (CSIRO) Materials Science and Engineering & Future Manufacturing Flagship Clayton, Victoria, Australia. E-mail:
[email protected]
Amanda Barnard is a Queen Elizabeth II Fellow and leader of the Virtual Nanoscience Laboratory at CSIRO in Australia. She received her BSc (Applied Physics) in 2001 and her PhD (Physics) in 2003 from the RMIT University, before going on to a two-year position as a Distinguished Postdoctoral Fellow in the Center for Nanoscale Materials at Argonne National Laboratory, followed Amanda Barnard by three years as a Fellow at the University of Oxford. Using thermodynamic theory and first principles computer simulations, her current research includes predicting the environmental stability of nanoparticles and their interactions with natural ecosystems. This journal is ª The Royal Society of Chemistry 2009
The next generation of ‘in-demand’ smart products must be efficient, safe and (in more and more cases) environmentally friendly. Above all else, they must also be reliable and perform their function in a predictable way. Many of the nanoparticles engineered for the tasks above have no natural analogue, and are often artificially modified to induce specific functionality. This introduces a certain degree of unpredictability, since we are presented with a range of untested materials that are (literally) unique on an atomic scale, with no historical data to guide our assumptions regarding the possible hazards. It is arrogant and irresponsible to say on one hand that nanomaterials are novel and provide a range of properties (and possible applications) not observed at other lengthscales, and yet on the other to say that all of the undesirable properties are all sufficiently predictable and pose no possible threat. There are cases where we can learn from nature, particularly in the areas of geomorphology and biotechnology, and there are entire areas of science already studying these cases. It is the cases where we cannot rely on these lessons that require specialist attention from the new fields of nanoscience and nanotechnology. In general, the risks associated with engineered nanomaterials are combinations of hazards (often described in terms of severity) and exposure (described in terms of the likelihood, frequency and duration). Hazards may manifest as undesirable interactions with biological systems such as cytotoxicity, oxidative stress in tissue, pulmonary disorders due to inhalation, inflammation due to accumulation and, at a more fundamental biological level, such phenomena as protein mis-folding and damage to DNA.8–10 Moreover, even if a certain nanoparticle does not appear toxic by itself, the interaction between this nanoparticle and other common compounds in the human body may cause serious problems to cell functions. In addition to this, hazards may also manifest as undesirable interactions with natural ecosystems, including the introduction of air- or water-born pollution, contamination of soils, detriment to the food chain and reactions leading to increases in salinity or chemical imbalances in natural resources that were not otherwise present before. This is by no means an exhaustive list, but is intended to illustrate the diversity encapsulated by this term. Nanoscale, 2009, 1, 89–95 | 89
In general, much of the study of toxicity of nanosized particles is based on established research on airborne ultra-fine particles. In the past, ultra-fine particles were known to either occur naturally, or be introduced through human activities or industrial products. This lead G€ unter, Eva and Jan Oberd€ orster to catalogue the natural and anthropogenic sources of nanoparticles (with average diameter
