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Summary: A series of fluorescent polystyrene latex particles with carboxyl and amino functionalities on their surface were synthesized by the miniemulsion technique. The fluorescent dye N‐(2,6‐diisopropylphenyl)perylene‐3,4‐dicarboximide (PMI) was incorporated into the copolymer nanoparticles formulated from styrene and acrylic acid or styrene and aminoethyl methacrylate hydrochloride. The resulting latexes were stable and showed a monodisperse size distribution. The particle size depended on the amount and nature of the functional comonomer and was in the range 100–175 nm. All latexes were characterized by transmission electron microscopy (TEM), dynamic light scattering, UV‐Vis spectroscopy and zeta potential measurements. The amount of surface functional groups was determined by electrolyte titration. Furthermore, the functionalized fluorescent particles were utilized as markers for HeLa cells and cell uptake was visualized using fluorescence microscopy. The correlation of the uptake of nanoparticles with the surface charge was determined by FACS measurements.Confocal fluorescent microscopy of HeLa cells after the uptake of amino functionalized particles (green).magnified imageConfocal fluorescent microscopy of HeLa cells after the uptake of amino functionalized particles (green).

Cell labeling by superparamagnetic iron oxide particles (SPIO) has emerged as a potentially powerful tool to monitor trafficking of transplanted cells by magnetic resonance tomography, e.g., in studies for tissue repair. However, intracellular labeling is mostly achieved by transfection agents not approved for clinical use. In this work, the feasibility and efficiency of labeling human mesenchymal stem cells (MSC) and HeLa cells with two commercially available SPIOs (Resovist and Feridex) without transfection agents was evaluated. In both cell types, Resovist without a transfection agent was more efficiently taken up than Feridex. Increasing the concentration of Resovist can yield similar amounts of iron in cells as SPIOs with transfection agents. This offers the opportunity to omit transfection agents from the labeling protocol when Resovist is used. Intracellular localization of the contrast agents is found by light microscopy and confirmed by electron microscopy. Coagulation of the SPIO nanoparticles, which is problematic for the quantification of the intracellular iron content, was observed and analyzed with a fluorescent activated cell sorter. As Resovist consists of a carboxydextran shell in contrast to Feridex which is composed of a dextran shell, we synthesized fluorescent polymeric nanoparticles as model systems with different amounts of carboxyl groups on the surface by the miniemulsion process. A steady increase in uptake of nanoparticles was detected with a higher density of carboxyl groups showing the relevance of charged groups as in the case of Resovist. Aggregation of these polymeric nanoparticles was not found.

As superparamagnetic nanoparticles capture new applications and markets, the flexibility and modifications of these nanoparticles are increasingly important aspects. Therefore a series of magnetic polystyrene particles encapsulating magnetite nanoparticles (10-12 nm) in a hydrophobic poly(styrene-co-acrylic acid) shell was synthesized by a three-step miniemulsion process. A high amount of iron oxide was incorporated by this process (typically 30-40%

Key Points ALPS DNT cells and their putative precursors reveal high proliferative activity in vivo, which is associated with hyperactive mTOR signaling. Rapamycin therapy controls mitotic activity and abnormal differentiation of ALPS DNT cells and reduces CD4+ or CD8+ precursor DNT cells.

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Key Points Germ line biallelic loss-of-function THPO mutations cause BMF. Marrow failure due to THPO mutations is characterized by poor graft function after transplantation but responds to THPO receptor agonists.