Nanotechnology has infiltrated a number of consumer markets and represents a rapidly expanding multibillion dollar global
market that is predicted by the US National Science foundation to be worth more than $1 trillion by 2015.1 In particular, nanotechnology has offered numerous benefits to the pharmaceutical and healthcare sectors, with many nanoenabled
medical products now readily available (Table 1). Other nanotech innovations, including carbon nanotubebased RNA, DNA, protein and drug delivery systems are also in development.3 Indeed, between 2004 and 2005 there was a 60% increase in the number of nano-enabled products in the development pipeline and around 1000 or so products on the global market.4
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Unfortunately, it is not yet clear whether nanomaterials may pose risks to human safety. Medically relevant nanomaterials
can be a mixture of particles with biologically important size, charge distribution and chemistry characteristics, which makes
it difficult to predict what effects they may have. In June 2007, the European Scientific Committee on Emerging and Newly
Identified Health Risks recommended that the potential risks of nanoparticles be considered in light of evidence that they
can cross biological barriers impervious to larger entities and their bulk equivalents;5 for instance, it is known that 20–50 nm nanoparticles can cross the blood brain–barrier and that 70 nm particles can cross
into the pulmonary system. In addition, spherical fullerenes appear to accumulate in the liver.6,7
Table 1: Examples of marketed nano-enabled medical products. Modified from Wagner et al., (2006).
In this article, we consider whether existing in vivo approaches are predictive of the effects of nanoenabled products on human patients. The prospects for replacing animal studies
with alternative models are also discussed.
For the purpose of this article, the term nanoparticle is used to describe a chemical, compound material or complex that has
a unit size in at least one-dimension that does not exceed 100 nm. Nanoenabled therapeutic delivery systems, diagnostic or
monitoring tools are nanodevices based on the definition of a medical device as given by the Medical Devices Directive 93/42/EEC.8