Acknowledgements
We wish to thank the participants in this study. This work was supported by EU JPND project SOPHIA, Fundação para a Ciência e a Tecnologia (FCT) [JPND/0003/2011], Portugal; Euronanomed 2 ERA-NET project GlioEx, FCT [ENMed/0001/2013]; iNOVA4Health, UI FCT/Ministério da Educação e Ciência [UID/Multi/04462/2013].
Declaration of interest
The authors report no conflicts of interest.
Supplementary material available online