Robert Branscheid

Controlled synthesis of linear and branched Au@ZnO hybrid nanocrystals and their photocatalytic properties

Colloidal Au@ZnO hybrid nanocrystals with linear and branched shape were synthesized. The number of ZnO domains on the Au seeds can be controlled by the solvent mixture. Imidazole-functionalized Au@ZnO hybrid nanocrystals were soluble in water and exhibited a greatly enhanced photocatalytic activity compared to ZnO nanocrystals. The pristine heterodimeric NPs were characterized using transmission electron microscopy (TEM), X-ray diffraction (XRD), and UV-Vis spectroscopy.

Unexpected multivalent display of proteins by temperature triggered self-assembly of elastin-like polypeptide block copolymers

We report herein the unexpected temperature triggered self-assembly of proteins fused to thermally responsive elastin-like polypeptides (ELPs) into spherical micelles. A set of six ELP block copolymers (ELP(BC)) differing in hydrophilic and hydrophobic block lengths were genetically fused to two single domain proteins, thioredoxin (Trx) and a fibronectin type III domain (Fn3) that binds the α(v)β(3) integrin. The self-assembly of these protein-ELP(BC) fusions as a function of temperature was investigated by UV spectroscopy, light scattering, and cryo-TEM. Self-assembly of the ELP(BC) was unexpectedly retained upon fusion to the two proteins, resulting in the formation of spherical micelles with a hydrodynamic radius that ranged from 24 to 37 nm, depending on the protein and ELP(BC). Cryo-TEM images confirmed the formation of spherical particles with a size that was consistent with that measured by light scattering. The bioactivity of Fn3 was retained when presented by the ELP(BC) micelles, as indicated by the enhanced uptake of the Fn3-decorated ELP(BC) micelles in comparison to the unimer by cells that overexpress the α(v)β(3) integrin. The fusion of single domain proteins to ELP(BC)s may provide a ubiquitous platform for the multivalent presentation of proteins.

Phase separated Cu@Fe3O4 heterodimer nanoparticles from organometallic reactants

Cu@Fe3O4 heteroparticles with distinct morphologies were synthesized from organometallic reactants. The shape of the magnetic domains could be controlled by the solvent and reaction conditions. They display magnetic and optical properties that are useful for simultaneous magnetic and optical detection. After functionalization, the Cu@Fe3O4 heterodimers become water soluble. The morphology, structure, magnetic and optical properties of the as-synthesized heterodimer nanoparticles were characterized using transmission electron microscopy (TEM), X-ray diffraction (XRD), mossbauer spectroscopy, superconducting quantum interference device (SQUID) magnetometry, and dark field imaging. A special advantage of these heterodimers lies in the fact that the nanodomains of different composition can be used e.g. for the formation of nitric oxide (NO) through the Cu domain and heterodimer nanoparticles can be removed from the reaction mixture by means of the magnetic domain (Fe3O4).

IVIVC for fenofibrate immediate release tablets using solubility and permeability as in vitro predictors for pharmacokinetics

The goal of this study was to investigate the in vitro-in vivo correlation (IVIVC) for fenofibrate immediate release (IR) tablet formulations based on MeltDose-technique. The in vitro determined drug solubility and permeability data were related to the C(max) values observed from two in vivo human studies. Solubility and permeation studies of fenofibrate were conducted in medium simulating the fasted state conditions in the upper jejunum, containing the surfactant compositions of the six formulations at different concentrations. The behavior of all surfactant compositions was characterized by surface tension, dynamic light scattering, and cryo-TEM. The obtained solubility and permeation data were combined and compared with the C(max) values for the fenofibrate formulations, assuming a 50 mL in vivo dissolution volume. A good IVIVC was observed for five fenofibrate formulations (R(2) = 0.94). The in vitro studies revealed that the formulation compositions containing sodium lauryl sulfate (SLS) interfered with the vesicular drug solubilizing system of the biorelevant medium and antagonized its solubilization capacity. The opposing interaction of surfactants with the emulsifying physiological constituents in intestinal juice should be taken into consideration in order to prevent unsatisfactory in vivo performance of orally administered formulations with low soluble active pharmaceutical ingredients.

Molecular Camouflage: Making Use of Protecting Groups To Control the Self‐Assembly of Inorganic Janus Particles onto Metal–Chalcogenide Nanotubes by Pearson Hardness

Hard and soft: Binding of inorganic Pt@Fe3O4 Janus particles to WS2 nanotubes through their Pt or Fe3O4 domains is governed by the difference in Pearson hardness: the soft Pt block has a higher sulfur affinity than the harder magnetite face; thus the binding proceeds preferentially through the Pt face. This binding preference can be reversed by masking the Pt face with an organic protecting group.

The interplay of crystallization kinetics and morphology during the formation of SnO2 nanorods: snapshots of the crystallization from fast microwave reactions

A microwave-assisted reaction pathway to rutile SnO2nanorods was investigated. The microwave-treatment significantly reduces the reaction time compared to standard hydro-/solvothermal techniques. By moving the overall process into a shorter time slot, the growth and crystal formation during the reaction could be monitored via snapshots by trapping the intermediates through quenching. To gain a better insight into the template-free growth of one-dimensional (1D) nanostructures, a parameter-dependent (various temperatures/pressures and times were investigated) study was carried out. For all materials, the phase purity and crystallite sizes were determined by X-ray powder diffraction (XRD). The growth-orientation and terminating crystal faces of the reaction intermediates were determined using (HR)-TEM measurements. A growth mechanism was proposed. The optical properties were studied by means of Raman and infrared spectroscopy.

Adsorption of the Herbicide 4-Chloro-2-methylphenoxyacetic Acid (MCPA) by Goethite

Interaction between the goethite surface and 4-chloro-2-methylphenoxyacetic acid (MCPA) herbicide was studied using density functional theory (DFT) calculations combined with molecular dynamics (MD). The important step made here lies in the use of a periodic DFT method enabling the study of a mineral surface of different protonation states, in strong contrast with previous molecular modeling studies limited to single protonation state corresponding to the point of zero charge. Different surface OH groups and MCPA proton states were used to mimic the strong effects of pH on the outer- and inner-sphere surface complexes that are theoretically possible, together with their binding energies, and their bond lengths. Modeling both a solvated and a protonated (110) goethite surface provided a major breakthrough in the acidic adsorption regime. An outer-sphere complex and a monodentate inner-sphere complex with the neutral MCPA molecule were found to be the most energetically stable adsorbate forms. MD modeling predicted that the latter forms via the sharing of the carbonyl oxygen between the MCPA carboxylate group and a singly coordinated surface hydroxyl group, releasing an H2O molecule. All the other complexes, including the bidentate inner-sphere complex, had higher relative energies and were therefore less likely. The two most likely DFT-optimized structures were used to constrain a surface complexation model applying the charge distribution multisite complexation (CD-MUSIC) approach. The adsorption constants for the complexes were successfully fitted to experimental batch equilibrium data.

Nanoparticle vesicles through self assembly of cyclodextrin- and adamantyl-modified silica.

Stable nanoparticle vesicles were for the first time prepared from adamantyl- and cyclodextrin (CD)-modified silica nanoparticles forming host-guest interactions in aqueous solution. Adamantyl-functionalized nanoparticles were obtained from thiol-isocyanate reaction of thiol-modified nanoparticles with 1-adamantyl isocyanate. The CD modified silica particles were isolated from a reaction of mono-6-para-toluenesulfonyl-β-cyclodextrin with the thiol functionalized silica under microwave conditions in basic media. The obtained particles were characterized in respect of agglomeration and self-assembly behavior in aqueous solution by dynamic light scattering and transmission electron microscopy. The found vesicle structures are exceptionally stable even after evaporation of water. Such inorganic hollow spheres formed through self-assembly processes may be important for chemical storage and transport. The technique of chemically-driven assembly is an attractive option to form useful complex structures by tunable agglomeration.

Controlling phase formation in solids: rational synthesis of phase separated Co@Fe2O3 heteroparticles and CoFe2O4 nanoparticles

A wet chemical approach from organometallic reactants allowed the targeted synthesis of Co@Fe(2)O(3) heterodimer and CoFe(2)O(4) ferrite nanoparticles. They display magnetic properties that are useful for magnetic MRI detection.

Soluble IF-ReS2 nanoparticles by surface functionalization with terpyridine ligands.

A major drawback in the application of layered chalcogenide nanoparticles/tubes is their inertness to chemical and biological modification and functionalization. Their potential use in composite materials might be greatly enhanced by improving the chalcogenide/matrix interface bonding. A novel modification strategy for layered chalcogenide nanoparticles based on the chalcophilic affinity of metals and the chelating terpyridine is reported. The terpyridine anchor group can be conjugated to fluorescent tags or hydrophilic/hydrophobic groups that confer solubility in various solvents to the otherwise insoluble chalcogenide nanoparticles. The functionalized particles are characterized using TEM/HRTEM, optical and vibrational spectroscopy, and confocal laser scanning microscopy.