The need for in situ characterisation in nanosafety assessment: funded transnational access via the QNano research infrastructure

The first concerns regarding potential toxicities of nanomaterials were raised almost 10 years ago, as fears that the small size of nanoparticles might allow them unique access to organisms, cells, cellular barriers and subcellular organelles with potentially harmful consequences resulting from quantum properties (Colvin 2003). Much has been learned in the intervening period, and indeed nanosafety assessment is almost at the stage of being a quantitative and mechanismbased scientific discipline, where nanoparticle dispersions can be generated reproducibly to ensure known nanoparticle doses are delivered (Ramirez-Garcia et al. 2011), nanoparticle uptake can be quantified and modelled (Elsaesser et al. 2010), and impacts from the presence of nanoparticles in cells and tissues can be teased out in a time-resolved manner (Xia et al. 2008). However, significant work is still needed to ensure that this knowledge becomes formulated into standardised and agreed protocols that are widely disseminated to the growing research community addressing topics related to nanosafety and the interactions of nanomaterials with living systems, be they intentional (e.g. nanomedicine) or unintended (e.g. nanoparticles produced via combustion). QNano, a Seventh Framework Programme Capacities project, is an analytical research infrastructure for characterisation of nanomaterials for nanosafety assessment (Grant agreement n INFRA-2010-262163) established in early 2011 to address this issue of formulating and disseminating best practice for nanosafety assessment. QNano consists of 29 funded and 25 additional partners from around Europe, with expertise ranging from nanomaterials synthesis, dispersion, labelling (with optical, isotope and radio-labels), characterisation of nanomaterials in both their pristine state and in situ in complex milieu (including in the environment and in consumer products), using a range of advanced techniques 1, as well as a suite of approaches for nanomaterials exposure assessment in both in vitro and in vivo models. QNano is an analytical infrastructure dedicated to quality in all aspects of nanomaterials safety assessment, with characterisation of the nanoparticles at all stages of exposure being a key focus, in order to connect the actual dose experienced by living systems with the observed impacts. A key pillar of activity within QNano is the provision of funded transnational access to approximately 400 researchers from the nanosafety and nanomedicine communities for characterisation of nanomaterials in situ. Each transnational access visit will be approximately 5–8 working days. The importance of characterisation of nanomaterials in the relevant biological dispersant (i.e. under the exposure conditions) is increasingly accepted as being necessary in order to determine the “available” nanoparticle dose. Scientists increasingly recognise that nanoparticles immediately absorb proteins or other biomolecules from their surroundings to lower their surface energy (Rivera Gil et al. 2010) with important consequences for nanoparticle stability in dispersion (Kendall et al. 2011). Note that for ecotoxicological studies, natural organic matter plays much the same role as proteins for in vitro and in vivo toxicology studies, modulating the nanoparticle surface (free energy) and thus the dispersibility of nanomaterials (Baalousha et al. 2008). As a consequence, nanoparticles dispersed in biofluids containing proteins, lipids, polysaccharides and so forth can have a very different dispersion profile than the same nanoparticles dispersed in reference buffers, as shown in Figure 1, which can lead to very different effective or available doses of nanoparticles for interaction with living systems. The composition of the biomolecule corona and the subsequent stability, available dose and consequent biological interactions of nanoparticles have been found to depend on the specific details of the biofluid in which the nanoparticles are dispersed, which may account for much of the contradictory reports present in the literature for nominally identical materials. Thus, the same (batch of) nanoparticles dispersed in different cell culture media (e.g. DMEM or RPMI) containing identical concentrations of foetal bovine serum (FBS) have been shown to result in quite different coronas, in terms of both their thickness and dynamics (Maiorano et al. 2010). The authors of that study observed that DMEM elicits the formation of a large time-dependent