Gold nanoparticles (AuNPs) have potential biomedical and scientific applications. In this study, we evaluated the uptake and internalization of FBS-coated 20 nm AuNPs into lung fibroblasts and liver cells by different microscopy techniques. AuNP aggregates were observed inside MRC5 lung fibroblasts and Chang liver cells under light microscopy, especially after enhancement with automegallography. Clusters of AuNPs were observed to be adsorbed on the cell surface by scanning electron microscopy. Ultrathin sections showed that AuNPs were mainly enclosed within cytoplasmic vesicles when viewed under transmission electron microscopy. We also investigated the mechanism of uptake for AuNPs, using endocytosis inhibitors and quantification of Au with inductively coupled plasma mass spectrometry. Cells treated with concanavalin A and chlorpromazine showed significant decrease of Au uptake in MRC5 lung fibroblasts and Chang liver cells, respectively, implying that the uptake of AuNPs was facilitated by clathrinmediated endocytosis. It would therefore appear that uptake of 20 nm AuNPs in both cell types with different tissues of origin, was dependent upon clathrin-mediated endocytosis. Anat Rec, 298:418-427, 2015. V C 2014 Wiley Periodicals, Inc.

opened the discussion of the paper by Peter Dobson: Is a size of below 20 nm critical to achieve cell penetration by nanoparticles? Peter Dobson responded: No, I chose this as a typical size. I believe that the most important point is the surface chemistry and that particle size could be a secondary factor. On the other hand, smaller particles of <20 nm will induce a distortion of the outer cell membrane enabling the particle to penetrate by endocytosis, but this requires a strong affinity brought about by the nanoparticlecell surface interaction. Ivan Parkin remarked: The antimicrobial properties of nanodiamond may have been misrepresented in the literature as the commercial solutions contain a variety of antimicrobial agents. Studies must make sure that these are not present if antimicrobial analyses are to be performed. Peter Dobson replied: I fully agree, but on the other hand nanodiamond has got unique energy levels with respect to water and related systems. 1

Sara Carreira opened the discussion of the paper by Nicolas Barry: Why are your RuMs and OsMs so specic to cancer cells without using any targeting moiety?Nicolas Barry replied: We believe that the specicity comes from the size of the particles -passive targeting. Clinically-validated therapeutic and imaging NPs usually target cancer cells in a passive way. This is achieved by taking advantage of the enhanced permeability and retention (EPR) effect in tumor tissues. Tumor vasculature is highly disorganised, compared to the vasculature in normal tissues, and the vascular endothelium in tumors proliferates rapidly and discontinuously. This results in a higher number of fenestrations and open junctions (from 200 nm to 1.2 mm) than in normal vessels. Particles with a typical size of a few nanometres can therefore passively cross the tumor endothelial barrier through fenestrations, and accumulate at particular sites through blood hemodynamic forces and diffusion mechanisms.One of our objectives is to increase the size of our particles from 15 nm to a few hundred nanometres, in order to maximize this passive targeting. We also wish to introduce an active targeting moiety (e.g. specic peptides, antibodies) on the corona of the particles to increase this selectivity.Peter Dobson asked: Have you looked to see if any of your compounds are luminescent?Nicolas Barry responded: There are numerous examples of ruthenium compounds that are luminescent. Usually, arene Ru(II) complexes are not luminescent owing to the arene-metal interactions. Nonetheless, it is possible to introduce a luminescent ligand (such as a pyrene derivative) by functionalizing the 16-electron complexes (to make an 18-electron complex).This journal is

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