Ceramides (Cer) are the central molecules in sphingolipid metabolism that participate in cellular signaling and also prevent excessive water loss by the skin. Previous studies showed that sphingosine-based Cer with a long 16C chain (CerNS16) and very long 24C-chain ceramides (CerNS24) differ in their biological actions. Increased levels of long CerNS16 at the expense of the very long CerNS24 have been found in atopic dermatitis patients, and this change correlated with the skin barrier properties. To probe the membrane behavior of the long CerNS16 and the very long chain CerNS24, we studied their interactions with fatty acids and cholesterol in model stratum corneum membranes using infrared spectroscopy. Using Cer with deuterated acyls and/or deuterated fatty acids, we showed differences in lipid mixing, packing, and thermotropic phase behavior between long and very long Cer. These differences were observed in the presence of lignoceric acid or a heterogeneous fatty acid mixture (C16-C24), in the presence or absence of cholesterol sulfate, and at 5-95% humidity. In these membranes, very long CerNS24 prefers an extended (splayed-chain) conformation in which the fatty acid is associated with the very long Cer chain. In contrast, the shorter CerNS16 and fatty acids are mostly phase separated.

Studies of the uptake, biological fate, and toxicity of several metal oxide nanoparticles (NPs), such as Al2O3, TiO2, CeO2‐x, and ZnO NPs undertaken in the European Project “Health Impact of Engineered Metal and Metal Oxide Nanoparticles: Response, Bioimaging and Distribution at Cellular and Body Level” are reviewed here. Metal oxide NPs are radiolabeled by direct proton bombardment of commercially available NPs or enriched during synthesis with 18O to generate 18F after‐proton bombardment. Size, degree of aggregation, and zeta potential of the metal oxide NPs are studied in the presence of proteins and cell media. NP uptake and intracellular fate are followed by ion beam microscopy (IBM), transmission electron microscopy, confocal Raman microscopy and confocal laser scanning microscopy. IBM allows for the quantification of the intracellular dose of NPs. Cell viability studies and the immune response are studied “in vitro” in primary alveoli, and immortalized cell lines. Biodistribution studies in rodents are performed with positron emission tomography following different exposure routes: intravenous, oral, topical, and inhalation using radiolabelled NPs. Activity per organ is quantified for the different uptake routes and with the time.

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Introduction: Nanoparticles (NPs) are used in numerous products in technical fields and biomedicine; their potential adverse effects have to be considered in order to achieve safe applications. Besides their distribution in tissues, organs, and cellular localization, their impact and penetration during the process of tissue formation occurring in vivo during liver regeneration are critical steps for establishment of safe nanomaterials. Materials and methods: In this study, 3D cell culture of human hepatocarcinoma cells (HepG2) was used to generate cellular spheroids, serving as in vitro liver microtissues. In order to determine their differential distribution and penetration depth in HepG2 spheroids, SiO 2 NPs were applied either during or after spheroid formation. The NP penetration was comprehensively studied using confocal laser scanning microscopy and scanning electron microscopy. Results: Spheroids were exposed to 100 µg mL −1 SiO 2 NPs either at the beginning of spheroid formation, or during or after formation of spheroids. Microscopy analyses revealed that NP penetration into the spheroid is limited. During and after spheroid formation, SiO 2 NPs penetrated about 20 µm into the spheroids, corresponding to about three cell layers. In contrast, because of the addition of SiO 2 NPs simultaneously to cell seeding, NP agglomerates were located also in the spheroid center. Application of SiO 2 NPs during the process of spheroid formation had no impact on final spheroid size. Conclusion: Understanding the distribution of NPs in tissues is essential for biomedical applications. The obtained results indicate that NPs show only limited penetration into already formed tissue, which is probably caused by the alteration of the tissue structure and cell packing density during the process of spheroid formation.

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Extraordinarily small (2.4 nm) cobalt ferrite nanoparticles (ESCIoNs) were synthesized by a one-pot thermal decomposition approach to study their potential as magnetic resonance imaging (MRI) contrast agents. Fine size control was achieved using oleylamine alone, and annular dark-field scanning transmission electron microscopy revealed highly crystalline cubic spinel particles with atomic resolution. Ligand exchange with dimercaptosuccinic acid rendered the particles stable in physiological conditions with a hydrodynamic diameter of 12 nm. The particles displayed superparamagnetic properties and a low r2/r1 ratio suitable for a T1 contrast agent. The particles were functionalized with bile acid, which improved biocompatibility by significant reduction of reactive oxygen species generation and is a first step toward liver-targeted T1 MRI. Our study demonstrates the potential of ESCIoNs as T1 MRI contrast agents.

Self-calibrating, fluorescent nanoparticles with diameter far below 50 nm are synthesized with embedding a new ratiometric and pH sensitive indicator dye. The prompt response of the fluorophore allows for determining the intracellular pH.

In this study, a novel approach for preparation of green fluorescent protein (GFP)-doped silica nanoparticles with a narrow size distribution is presented. GFP was chosen as a model protein due to its autofluorescence. Protein-doped nanoparticles have a high application potential in the field of intracellular protein delivery. In addition, fluorescently labelled particles can be used for bioimaging. The size of these protein-doped nanoparticles was adjusted from 15 to 35 nm using a multistep synthesis process, comprising the particle core synthesis followed by shell regrowth steps. GFP was selectively incorporated into the silica matrix of either the core or the shell or both by a one-pot reaction. The obtained nanoparticles were characterised by determination of particle size, hydrodynamic diameter, ζ-potential, fluorescence and quantum yield. The measurements showed that the fluorescence of GFP was maintained during particle synthesis. Cellular uptake experiments demonstrated that the GFP-doped nanoparticles can be used as stable and effective fluorescent probes. The study reveals the potential of the chosen approach for incorporation of functional biological macromolecules into silica nanoparticles, which opens novel application fields like intracellular protein delivery.Electronic supplementary materialThe online version of this article (10.1186/s11671-017-2280-9) contains supplementary material, which is available to authorized users.