How shape influences uptake: interactions of anisotropic polymer nanoparticles and human mesenchymal stem cells.

Among several nanoparticle properties, shape is important for their interaction with cells and, therefore, relevant for uptake studies and applications. In order to further investigate such characteristics, fluorescently labeled spherical polymer nanoparticles are synthesized by free-radical polymerization via the miniemulsion process. The spherical nanoparticles are subsequently submitted to controlled mechanical deformation to yield quasi-ellipsoidal polymeric nanoparticles with different aspect ratios. The uptake behaviors of spherical and non-spherical particles with equal volume are investigated qualitatively and quantitatively by electron microscopy, confocal laser scanning microscopy, and flow cytometry measurements. Non-spherical particles show fewer uptake by cells than their spherical counterparts with a negative correlation between aspect ratio and uptake rate. This is attributed to the larger average curvature radius of adsorbed non-spherical particles experienced by the cells.

Ceria/silicon carbide core-shell materials prepared by miniemulsion technique.

For the first time we present the synthesis of CeO(2)/Si(O)C core-shell particles prepared by the miniemulsion technique. The Si(O)C core was obtained by means of a polycarbosilane precursor (SMP10), which was subsequently functionalized with ceria and pyrolyzed to the ceramic. The size of these particles could easily be adjusted by varying the surfactants and the surfactant concentration, or by the addition of comonomers. Hence particle sizes ranged from 100 to 1000 nm, tunable by the preparation conditions. All materials were characterized by photon cross correlation spectroscopy, scanning electron microscopy and elemental mapping investigations. Furthermore, first catalytic tests were carried out by temperature programmed oxidation (TPO) of methane, and the activity of this material in lowering the onset temperature of methane combustion by 262 K was documented.

Structure formation in metal complex/polymer hybrid nanomaterials prepared by miniemulsion.

Polymer/complex hybrid nanostructures were prepared using a variety of hydrophobic metal ß-diketonato complexes. The mechanism of structure formation was investigated by electron paramagnetic resonance (EPR) spectroscopy and small-angle X-ray scattering (SAXS) in the liquid phase. Structure formation is attributed to an interaction between free coordination sites of metal ß-diketonato complexes and coordinating anionic surfactants. Lamellar structures are already present in the miniemulsion. By subsequent polymerization the lamellae can be embedded in a great variety of different polymeric matrices. The morphology of the lamellar structures, as elucidated by transmission electron microscopy (TEM), can be controlled by the choice of anionic surfactant. Using sodium alkylsulfates and sodium dodecylphosphate, "nano-onions" are formed, while sodium carboxylates lead to "kebab-like" structures. The composition of the hybrid nanostructures can be described as bilayer lamellae, embedded in a polymeric matrix. The metal complexes are separated by surfactant molecules which are arranged tail-to-tail; by increasing the carbon chain length of the surfactant the layer distance of the structured nanomaterial can be adjusted between 2 and 5 nm.

Interfacial activity of metal ß-diketonato complexes: in situ generation of amphiphiles by water coordination.

Symmetric transition metal complexes of 2,4-pentanedione (acetyl acetone) are interfacially active: Spinning drop tensiometry reveals lowering of the interfacial tension at the water-organic interface, most pronounced for [Cr(acac)(3)], [Fe(acac)(3)], [Zr(acac)(4)], and [Hf(acac)(4)]. The interfacial activity is explained by the in situ generation of amphiphilic species. Based on tensiometry and (1)H and diffusion-ordered NMR spectroscopy (DOSY NMR), hydrogen bonding of the organically dissolved complexes with water, in some cases in combination with inner-sphere hydrolytic coordination, is identified as the primary origin of this amphiphilicity. The complexes are a rare example of symmetric molecules that turn amphiphilic only upon interfacial interaction with water.

The softer and more hydrophobic the better: influence of the side chain of polymethacrylate nanoparticles for cellular uptake.

Intracellular uptake of nanoparticles is highly interesting for labeling of cells, drug delivery, or non-viral gene delivery. In this study we have synthesized a wide variety of poly(alkyl methacrylate) nanoparticles with the same size and investigated their uptake into cells. The nanoparticles were prepared from alkylmethacrylates with different linear and branched ester chains as well as from benzylmethacrylate using the miniemulsion polymerizaiton technique. By adding a fluorescent dye as a marker, the internalization of the nanoparticles could be investigated quantitatively with flow cytometry and qualitatively with confocal laser scanning microscopy. With increasing side chain of the ester and therefore increasing hydrophobicity and at glass transition temperature (T(g)), below the incubation temperature of 37 degrees C the uptake of the nanoparticles into cells is favored.