Functionalized gold nanoparticles: a detailed in vivo multimodal microscopic brain distribution study† Fernanda Sousa,‡ a Subhra Mandal, b Chiara Garrovo, a Alberto Astolfo, c Alois Bonifacio, d Diane Latawiec,x e Ralf Hendrik Menk, f Fulvia Arfelli, cg Sabine Huewel, h Giuseppe Legname, e Hans-Joachim Galla h and Silke Krol‡ * a Received 27th May 2010, Accepted 10th August 2010 DOI: 10.1039/c0nr00345j In the present study, the in vivo distribution of polyelectrolyte multilayer coated gold nanoparticles is shown, starting from the living animal down to cellular level. The coating was designed with functional moieties to serve as a potential nano drug for prion disease. With near infrared time-domain imaging we followed the biodistribution in mice up to 7 days after intravenous injection of the nanoparticles. The peak concentration in the head of mice was detected between 19 and 24 h. The precise particle distribution in the brain was studied ex vivo by X-ray microtomography, confocal laser and fluorescence microscopy. We found that the particles mainly accumulate in the hippocampus, thalamus, hypothalamus, and the cerebral cortex. Introduction A large number of compounds of pharmaceutical interest are tested nowadays for the treatment of neurodegenerative disor- ders. However, most of these compounds which demonstrate efficacy in vitro are not able to reach the central nervous system (CNS), at least not in pharmacologically significant concentra- tions. 1 Delivery of therapeutic agents to the CNS is hindered by the blood–brain barrier (BBB), which is composed of a tightly sealed layer of endothelial cells and astrocytes, regulating the permeation and diffusion of drugs from the blood stream into the brain. 1,2 Different approaches to deliver to the CNS compounds that do not normally cross the BBB have been attempted by various research groups. One approach is the temporary opening of the tight junctions using a hyperosmolaric solution. 3 However, this technique carries serious adverse effects associated with the frequency of administration of these hyperosmolar agents. Other approaches involve the direct delivery of therapeutics into the brain by intracerebral injection into the cerebral parenchyma or cerebral ventricles. Notwithstanding that these are invasive approaches associated with adverse tissue reaction and hae- morrhage, the amount of therapeutic agents that can be administered at one time is very limited and may also be subject to limited diffusion of the agents away from the injection site. 2–4 The barrier function of the BBB is not absolute, as the brain needs nutrients, oxygen and essential molecules. Complex and highly regulated, the BBB screens the biochemical, physico- chemical and structural features of solutes in its periphery, thus affording barrier selectivity in the passage of molecules into the brain parenchyma. Their passage may be mediated by simple diffusion or specific transport (adsorptive, receptor- or carrier- mediated transport mechanisms), both of which can be affected by interactions in the blood compartment (outside the BBB) and within the endothelial cells (at the BBB level). 5–8 With the growing knowledge about the nature of these mechanisms, several current delivery and targeting strategies are designed to use existing pathways. They include the development of hydrophobic or receptor-mediated prodrugs (drug molecules covalently bound either to a hydrophobic linker or to glucose molecules) which are cleaved in the brain, or liposomal drug preparation and even targeting moieties can be bound, such as antibodies. 9–12 However, despite the fact that some of these approaches have achieved increased drug delivery into the brain, the therapeutic efficacy decreases either due to chemical modifi- cations or a low drug load, thus limiting their usefulness. Polyelectrolyte multilayer coated nanoparticles are promising candidates as drug carriers, thanks to their ability to adsorb and incorporate drug molecules, resulting in a high local drug concentration sufficient to treat a small number of cells in the direct vicinity of the particles, and the possibility of engineering the surface functionalities for specific targeting. Gold nano- particles were chosen here as the core due to the fact that they are non-toxic in the selected size range, monodisperse and easy to functionalize through polyelectrolyte multilayer encapsulation. 13–15 a NanoBioMed Lab @ LANADA (Laboratory for Nanodiagnostics, Drug Delivery and Analysis), CBM - Cluster in Biomedicine S.c.r.l., Basovizza, AREA Science Park, Trieste, Italy. E-mail: silke.krol@istituto-besta.it b SISSA - Scuola Internazionale Superiore di Studi Avanzati -International School of Advanced Studies, Trieste, Italy c Department of Physics, University of Trieste, Trieste, Italy d Centre of Excellence for Nanostructured Materials, University of Trieste, Trieste, Italy e Laboratory of Prion Biology, Neurobiology Sector, Scuola Internazionale Superiore di Studi Avanzati - International School of Advanced Studies, AREA Science Park, Trieste, Italy f Sincrotrone Trieste S.C.p.A. di Interesse Nazionale, AREA Science Park, Trieste, Italy g INFN-Istituto Nationale di Fisica Nucleare, Trieste, Italy h Institute for Biochemistry, Westf, Wilhelms-University, Muenster, Germany † Electronic supplementary information (ESI) available: Fig. S1–S6. See DOI: 10.1039/c0nr00345j ‡ Present address: European Center for Nanomedicine, Neurological Institute ‘‘Carlo Besta’’, IFOM-IEO-campus, Milan, Italy. x Present address: NIHR Pancreatic Biomedical Unit at the Royal Liverpool University Hospital, Liverpool, UK. 2826 | Nanoscale, 2010, 2, 2826–2834 This journal is ª The Royal Society of Chemistry 2010 PAPER www.rsc.org/nanoscale | Nanoscale Published on 15 October 2010. Downloaded on 30/09/2013 17:44:22. View Article Online / Journal Homepage / Table of Contents for this issue