The uptake of polyelectrolyte multilayer coated colloids into cells, subsequent defoliation and plasmid delivery was studied by means of confocal microscopy and flow cytometry. Silica particles coated layer-wise with protamine and dextran sulfate were given to HEK 293T cells. Optimum uptake was found with protamine as the top layer. The particle uptake likely follows an non-receptor-mediated endocytotic pathway. Defoliation of polyelectrolyte multilayer coated particles within cells was demonstrated by the release of incorporated plasmids as indicated by the expression of plasmid encoded proteins using the enhanced green fluorescence proteine (pEGFP-C1) plasmid and a red fluorescence protein (pDsRed1-N1) plasmid. This proves, together with the direct observation of fluorescent layer debris, the defoliation of coated particles and the release of layer components into the cytoplasm. Particle uptake and GFP expression.

Polyelectrolyte multilayer sensor capsules, 5 microm in diameter, which contained fluorescein-labeled poly(acrylic acid) (PAAAF) as pH-sensitive reporter molecules, were fabricated and employed to explore their endocytotic uptake into HEK 293T cells by flow cytometry. The percentage of capsules residing in the endolysosomal compartment was estimated from the fluorescence intensity decrease caused by acidification. Capsules attached to the extracellular surface of the plasma membrane were identified by trypan blue quenching. The number of capsules in the cytoplasm was rather small, being below the detection limit of the method. The advantages of polyelectrolyte multilayer capsules are that the fluorophore is protected from interaction with cellular compartments and that the multilayer can be equipped with additional functions.

Cover: Silica particles can be coated layerwise with polyelectrolytes. Using the plasmid encoding the green fluorescent protein (pEGFP-C1) as a layer constituent particle uptake, release of particles into cytoplasm and defoliation of the polyelectrolyte multilayer are demonstrated by GFP expression in HEK 293T cells. Further details can be found in the Full Paper by U. Reibetanz, C. Claus, E. Typlt, J. Hofmann, and E. Donath* on page 153.

Multifunctional colloidal microparticles allow the integration of various active agents as well as reporter molecules into one system without interfering combining delivery and sensing functions. In this study, calcium carbonate particles were functionalized with fluorescein isothiocyanate-labeled poly(allylamine hydrochloride) (FITC-PAH) allowing particle localization in cell compartments of different pH. Plasmid DNA (pEGFP-C1 and pDsRed1-N1) as a reporter agent for drug release in the cytoplasm and rhodamine-B-isothiocyanate-labeled protamine (RITC-PRM) were integrated into biocompatible and biodegradable PRM/DXS multilayers. The uptake and processing of the particles by HEK293T/17 cells were investigated via flow cytometry and confocal laser scanning microscopy. The presented data show a clear correlation between the fluorescence intensity of the FITC-labeled core, that is, the particle localization after cellular uptake, and the expression of fluorescent proteins by the cells without further cell staining. In conclusion, this particle design allows the simultaneous study of particle location and processing to monitor the transport and release of active agents and should thus be an invaluable tool for the study and design of nano- and microcarrier systems.

bMitochondria are important for the viral life cycle, mainly by providing the energy required for viral replication and assembly. A highly complex interaction with mitochondria is exerted by rubella virus (RV), which includes an increase in the mitochondrial membrane potential as a general marker for mitochondrial activity. We aimed in this study to provide a more comprehensive picture of the activity of mitochondrial respiratory chain complexes I to IV. Their activities were compared among three different cell lines. A strong and significant increase in the activity of mitochondrial respiratory enzyme succinate:ubiquinone oxidoreductase (complex II) and a moderate increase of ubiquinol:cytochrome c oxidoreductase (complex III) were detected in all cell lines. In contrast, the activity of mitochondrial respiratory enzyme cytochrome c oxidase (complex IV) was significantly decreased. The effects on mitochondrial functions appear to be RV specific, as they were absent in control infections with measles virus. Additionally, these alterations of the respiratory chain activity were not associated with an elevated transcription of oxidative stress proteins, and reactive oxygen species (ROS) were induced only marginally. Moreover, protein and/or mRNA levels of markers for mitochondrial biogenesis and structure were elevated, such as nuclear respiratory factors (NRFs) and mitofusin 2 (Mfn2). Together, these results establish a novel view on the regulation of mitochondrial functions by viruses. Mitochondria are required for the maintenance of cell function and integrity. Their most important role lies in energy production, but they are also at the intersection of regulatory pathways that coordinate metabolic processes (e.g., calcium homeostasis and cellular proliferation), cellular fate (apoptosis and necrosis), and antiviral defense (1, 2). Even a participation of mitochondria in the innate immune response was identified (2). There are a number of viruses that interfere with the important role of mitochondria in cellular antiviral response pathways, mainly with the regulation of apoptosis (1). Additionally, as the powerhouses of the cell, mitochondria provide most of the energy for viral replication and assembly. Up to 90% of the cellular ATP is produced in the inner mitochondrial membrane (IMM) by oxidative phosphorylation (OXPHOS), (3). OXPHOS comprises a series of redox reactions carried out by four multisubunit enzyme complexes (complexes I to IV) of the electron transport chain (ETC). Electrons are transferred in a stepwise manner through this series of electron carriers from NADH (and FADH 2 ) as reducing equivalents to the final acceptor molecular oxygen. A small percentage of electrons that are transported through the respiratory complexes leaks out, which results in generation of reactive oxygen species (ROS). The main ROS species is hydrogen peroxide, which is converted to water by enzymes such as catalase, peroxiredoxin, or glutathione peroxidase as components of the cellular antioxidant system. Respiratory c...