Discovery of the primary aphid (Hemiptera: Aphidomorpha) and scale insect (Hemiptera: Coccomorpha) type specimens from the collection of Theodor Hartig (18051880).

Theodor Hartigs aphid and scale insect type specimens have been presumed lost or destroyed for the last 140 years. Here we document their discovery at the Bavarian State Collection of Zoology (Zoologische Staatssammlung Mnchen, ZSM), in Munich, Germany. These specimens include primary types for 24 aphid, three adelgid, and two armored scale insect species named by Hartig between 1834 and 1851, as well as other specimens of unknown importance.

Coordination Cage-Based Emulsifiers: Templated Formation of Metal Oxide Microcapsules Monitored by In Situ LC-TEM.

Metallo-supramolecular self-assembly has yielded a plethora of discrete nanosystems, many of which show competence in capturing guests and catalyzing chemical reactions. However, the potential of low-molecular bottom-up self-assemblies in the development of structured inorganic materials has rarely been methodically explored so far. Herein, we present a new type of metallo-supramolecular surfactant with the ability to stabilize non-aqueous emulsions for a significant period. The molecular design of the surfactant is based on a heteroleptic coordination cage (CGA-3; CGA=Cage-based Gemini Amphiphile), assembled from two pairs of organic building blocks, grouped around two Pd(II) cations. Shape-complementarity between the differently functionalized components generates discrete amphiphiles with a tailor-made polarity profile, able to stabilize non-aqueous emulsions, such as hexadecane-in-DMSO. These emulsions were used as a medium for the synthesis of spherical metal oxide microcapsules (titanium oxide, zirconium oxide, and niobium oxide) from soluble, water-sensitive alkoxide precursors by allowing a controlled dosage of water to the liquid-liquid phase boundary. Synthesized materials were analyzed by a combination of electron microscopic techniques. In situ liquid cell transmission electron microscopy (LC-TEM) was utilized for the first time to visualize the dynamics of the emulsion-templated formation of hollow inorganic titanium oxide and zirconium oxide microspheres.

Surfactant-loaded capsules as Marangoni microswimmers at the air-water interface: Symmetry breaking and spontaneous propulsion by surfactant diffusion and advection.

We present a realization of a fast interfacial Marangoni microswimmer by a half-spherical alginate capsule at the air-water interface, which diffusively releases water-soluble spreading molecules (weak surfactants such as polyethylene glycol (PEG)), which act as "fuel" by modulating the air-water interfacial tension. For a number of different fuels, we can observe symmetry breaking and spontaneous propulsion although the alginate particle and emission are isotropic. The propulsion mechanism is similar to soap or camphor boats, which are, however, typically asymmetric in shape or emission to select a swimming direction. We develop a theory of Marangoni boat propulsion starting from low Reynolds numbers by analyzing the coupled problems of surfactant diffusion and advection and fluid flow, which includes surfactant-induced fluid Marangoni flow, and surfactant adsorption at the air-water interface; we also include a possible evaporation of surfactant. The swimming velocity is determined by the balance of drag and Marangoni forces. We show that spontaneous symmetry breaking resulting in propulsion is possible above a critical dimensionless surfactant emission rate (Peclet number). We derive the relation between Peclet number and swimming speed and generalize to higher Reynolds numbers utilizing the concept of the Nusselt number. The theory explains the observed swimming speeds for PEG-alginate capsules, and we unravel the differences to other Marangoni boat systems based on camphor, which are mainly caused by surfactant evaporation from the liquid-air interface. The capsule Marangoni microswimmers also exhibit surfactant-mediated repulsive interactions with walls, which can be qualitatively explained by surfactant accumulation at the wall.

Effects of Chirality on the Aggregation Properties of Amide-Bonded Pyridinium Gemini Surfactants.

In a series of experiments, we synthesized and characterized a new type of cationic gemini surfactant, the chiral and the achiral forms, which were compared regarding their surface-active properties. These surfactants show interesting aggregation processes, which are affected by the interplay of different structural characteristics. By substituting the counterions, we found a way to control the solubility of these compounds in order to investigate the behavior of solutions as well as insoluble monolayers. The comparison of the chiral with the meso compound instead of the racemic mixture is a major advantage for the analysis of the effects of chirality because racemates can be understood as a mixed surfactant system with one additional degree of Gibbs freedom. Furthermore, we investigated the viscoelastic behavior of concentrated aqueous surfactant solutions which formed elongated wormlike micelles. A strong effect of the stereochemistry on the aggregation properties of Langmuir layers as well as elongated micelles was found.

Rational Design of an Amphiphilic Coordination Cage-Based Emulsifier.

Self-assembled, porous coordination cages with a functional interior find application in controlled guest inclusion/release, drug delivery, separation processes, and catalysis. However, only few studies exist that describe their utilization for the development of self-assembled materials based on their 3-dimensional shape and external functionalization. Here, dodecyl chain-containing, acridone-based ligands (LA) and shape-complementary phenanthrene-derived ligands (LB) are shown to self-assemble to heteroleptic coordination cages cis-[Pd2(LA)2(LB)2]4+ acting as a gemini amphiphile (CGA-1; Cage-based Gemini Amphiphile-1). Owing to their anisotropic decoration with short polar and long nonpolar side chains, the cationic cages were found to assemble into vesicles with diameters larger than 100 nm in suitable polar solvents, visualized by cryo-TEM and Liquid-Cell Transmission Electron Microscopy (LC-TEM). LC-TEM reveals that these vesicles aggregate into chains and necklaces via long-range interactions. In addition, the cages show a rarely described ability to stabilize oil-in-oil emulsions.

Strong Deformation of Ferrofluid-Filled Elastic Alginate Capsules in Inhomogenous Magnetic Fields.

We present a new system based on alginate gels for the encapsulation of a ferrofluid drop, which allows us to create millimeter-sized elastic capsules that are highly deformable by inhomogeneous magnetic fields. We use a combination of experimental and theoretical work in order to characterize and quantify the deformation behavior of these ferrofluid-filled capsules. We introduce a novel method for the direct encapsulation of unpolar liquids by sodium alginate. By adding 1-hexanol to the unpolar liquid, we can dissolve sufficient amounts of CaCl2 in the resulting mixture for ionotropic gelation of sodium alginate. The addition of polar alcohol molecules allows us to encapsulate a ferrofluid as a single phase rather than an emulsion without impairing ferrofluid stability. This encapsulation method increases the amount of encapsulated magnetic nanoparticles resulting in high deformations of approximately 30% (in height-to-width ratio) in inhomogeneous magnetic field with magnetic field variations of 50 mT over the size of the capsule. This offers possible applications of capsules as actuators, switches, or valves in confined spaces like microfluidic devices. We determine both elastic moduli of the capsule shell, Young's modulus and Poisson's ratio, by employing two independent mechanical methods, spinning capsule measurements and capsule compression between parallel plates. We then show that the observed magnetic deformation can be fully understood from magnetic forces exerted by the ferrofluid on the capsule shell if the magnetic field distribution and magnetization properties of the ferrofluid are known. We perform a detailed analysis of the magnetic deformation by employing a theoretical model based on nonlinear elasticity theory. Using an iterative solution scheme that couples a finite element/boundary element method for the magnetic field calculation to the solution of the elastic shape equations, we achieve quantitative agreement between theory and experiment for deformed capsule shapes using the Young modulus from mechanical characterization and the surface Poisson ratio as a fit parameter. This detailed analysis confirms the results from mechanical characterization that the surface Poisson ratio of the alginate shell is close to unity, that is, deformations of the alginate shell are almost area conserving.

Adsorption Behavior of Lysozyme at Titanium Oxide-Water Interfaces.

We present an in situ X-ray reflectivity study of the adsorption behavior of the protein lysozyme on titanium oxide layers under variation of different thermodynamic parameters, such as temperature, hydrostatic pressure, and pH value. Moreover, by varying the layer thickness of the titanium oxide layer on a silicon wafer, changes in the adsorption behavior of lysozyme were studied. In total, we determined less adsorption on titanium oxide compared with silicon dioxide, while increasing the titanium oxide layer thickness causes stronger adsorption. Furthermore, the variation of temperature from 20 to 80 °C yields an increase in the amount of adsorbed lysozyme at the interface. Additional measurements with variation of the pH value of the system in a region between pH 2 and 12 show that the surface charge of both protein and titanium oxide has a crucial role in the adsorption process. Further pressure-dependent experiments between 50 and 5000 bar show a reduction of the amount of adsorbed lysozyme with increasing pressure.

Human Apolipoprotein A1 at Solid/Liquid and Liquid/Gas Interfaces.

An X-ray reflectivity study on the adsorption behavior of human apolipoprotein A1 (apoA1) at hydrophilic and hydrophobic interfaces is presented. It is shown that the protein interacts via electrostatic and hydrophobic interactions with the interfaces, resulting in the absorption of the protein. pH dependent measurements at the solid/liquid interface between silicon dioxide and aqueous protein solution show that in a small pH range between pH 4 and 6, adsorption is increased due to electrostatic attraction. Here, the native shape of the protein seems to be conserved. In contrast, the adsorption at the liquid/gas interface is mainly driven by hydrophobic effects, presumably by extending the hydrophobic regions of the amphipathic helices, and results in a conformational change of the protein during adsorption. However, the addition of differently charged membrane-forming lipids at the liquid/gas interface illustrates the ability of apoA1 to include lipids, resulting in a depletion of the lipids from the interface.

Production, deformation and mechanical investigation of magnetic alginate capsules.

In this article we investigated the deformation of alginate capsules in magnetic fields. The sensitivity to magnetic forces was realised by encapsulating an oil in water emulsion, where the oil droplets contained dispersed magnetic nanoparticles. We solved calcium ions in the aqueous emulsion phase, which act as crosslinking compounds for forming thin layers of alginate membranes. This encapsulating technique allows the production of flexible capsules with an emulsion as the capsule core. It is important to mention that the magnetic nanoparticles were stable and dispersed throughout the complete process, which is an important difference to most magnetic alginate-based materials. In a series of experiments, we used spinning drop techniques, capsule squeezing experiments and interfacial shear rheology in order to determine the surface Young moduli, the surface Poisson ratios and the surface shear moduli of the magnetically sensitive alginate capsules. In additional experiments, we analysed the capsule deformation in magnetic fields. In spinning drop and capsule squeezing experiments, water droplets were pressed out of the capsules at elevated values of the mechanical load. This phenomenon might be used for the mechanically triggered release of water-soluble ingredients. After drying the emulsion-filled capsules, we produced capsules, which only contained a homogeneous oil phase with stable suspended magnetic nanoparticles (organic ferrofluid). In the dried state, the thin alginate membranes of these particles were rather rigid. These dehydrated capsules could be stored at ambient conditions for several months without changing their properties. After exposure to water, the alginate membranes rehydrated and became flexible and deformable again. During this swelling process, water diffused back in the capsule. This long-term stability and rehydration offers a great spectrum of different applications as sensors, soft actuators, artificial muscles or drug delivery systems.

Pendant capsule elastometry.

We provide a C/C++ software for the shape analysis of deflated elastic capsules in a pendant capsule geometry, which is based on an elastic description of the capsule material as a quasi two-dimensional elastic membrane using shell theory. Pendant capsule elastometry provides a new in situ and non-contact method for interfacial rheology of elastic capsules that goes beyond determination of the Gibbs- or dilational modulus from area-dependent measurements of the surface tension using pendant drop tensiometry, which can only give a rough estimate of the elastic capsule properties as they are based on a purely liquid interface model. Given an elastic model of the capsule membrane, pendant capsule elastometry determines optimal elastic moduli by fitting numerically generated axisymmetric shapes optimally to an experimental image. For each digitized image of a deflated capsule elastic moduli can be determined, if another image of its undeformed reference shape is provided. Within this paper, we focus on nonlinear Hookean elasticity because of its low computational cost and its wide applicability, but also discuss and implement alternative constitutive laws. For Hookean elasticity, Young's surface modulus (or, alternatively, area compression modulus) and Poisson's ratio are determined; for Mooney-Rivlin elasticity, the Rivlin modulus and a dimensionless shape parameter are determined; for neo-Hookean elasticity, only the Rivlin modulus is determined, using a fixed dimensionless shape parameter. Comparing results for different models we find that nonlinear Hookean elasticity is adequate for most capsules. If series of images are available, these moduli can be evaluated as a function of the capsule volume to analyze hysteresis or aging effects depending on the deformation history or to detect viscoelastic effects for different volume change rates. An additional wrinkling wavelength measurement allows the user to determine the bending modulus, from which the layer thickness can be derived. We verify the method by analyzing several materials, compare the results to available rheological measurements, and review several applications. We make the software available under the GPL license at github.com/jhegemann/opencapsule.

Salt induced reduction of lysozyme adsorption at charged interfaces.

A study of lysozyme adsorption below a behenic acid membrane and at the solid-liquid interface between aqueous lysozyme solution and a silicon wafer in the presence of sodium chloride is presented. The salt concentration was varied between 1 mmol L(-1) and 1000 mmol L(-1). X-ray reflectivity data show a clear dependence of the protein adsorption on the salt concentration. Increasing salt concentrations result in a decreased protein adsorption at the interface until a complete suppression at high concentrations is reached. This effect can be attributed to a reduced attractive electrostatic interaction between the positively charged proteins and negatively charged surfaces by charge screening. The measurements at the solid-liquid interfaces show a transition from unoriented order of lysozyme in the adsorbed film to an oriented order with the short protein axis perpendicular to the solid-liquid interface with rising salt concentration.

Magneto-responsive alginate capsules.

Upon incorporation of magnetic nanoparticles (mNPs) into gels, composite materials called ferrogels are obtained. These magneto-responsive systems have a wide range of potential applications including switches and sensors as well as drug delivery systems. In this article, we focus on the properties of calcium alginate capsules, which are widely used as carrier systems in medicine and technology. We studied the incorporation of different kinds of mNPs in matrix capsules and in the core and the shell of hollow particles. We found out that not all particle-alginate or particle-CaCl2 solution combinations were suitable for a successful capsule preparation on grounds of a destabilization of the nanoparticles or the polymer. For those systems allowing the preparation of switchable beads or capsules, we systematically studied the size and microscopic structure of the capsules, their magnetic behavior and mechanical resistance.

About the role of surfactants on the magnetic control over liquid interfaces.

The behavior of magnetically responsive aqueous Fe(III) surfactant solutions at liquid interfaces is analyzed. Such surfactants attracted much attention, because of the ability to manipulate interfaces by magnetic fields without any use of magnetic nanoparticles. A detailed analysis of the surface properties proves that the mixing of paramagnetic electrolyte solution with anionic, cationic and nonionic surfactants yields the similar magnetic response and no effect of the surfactant charge can be observed. We conclude that the observed magnetic shiftability of interfaces is caused by a combination of the paramagnetic behavior of the bulk liquid and a reduction of the surface tension. Thus, this work gives an alternative interpretation of the properties of "magnetic surfactants" compared to the ones claimed in the literature.

Exploring the synthesis of a new group of chiral ammonium salts with specific configurations at the stereogenic nitrogen centers.

A group of new chiral dications with a fixed, specific configuration at the stereogenic nitrogen center was created. Stereoselective synthesis and recrystallization give the diastereomerically and enantiomerically pure dications, including a chiral amphiphile with surface-active properties.

Is the antioxidative effectiveness of a bilberry extract influenced by encapsulation?

BACKGROUND: Bilberries (Vaccinium myrtillus L.) have been suggested to have preventive properties against diseases associated with oxidative stress such as colon cancer or inflammatory bowel diseases. Therefore the gastrointestinal tract is regarded as a potential target for prevention. In this study the antioxidative properties of a commercially available anthocyanin-rich bilberry extract (BE) were investigated in comparison with four different BE-loaded microcapsule systems. As markers to describe the antioxidant status in this cellular system, intracellular reactive oxygen species (ROS) levels, oxidative DNA damage and total glutathione (tGSH) levels were monitored. RESULTS: Incubations with the BE-loaded capsule systems showed an increase in cellular glutathione levels and reduction of ROS levels at high BE concentrations (100-500 µg mL(-1) ) and a positive effect on the formation of DNA strand breaks (5-10 µg mL(-1) BE). The biological properties of BE-loaded pectin amide core-shell capsules, whey protein matrix capsules and coated apple pectin matrix capsules were comparable to those of the non-encapsulated BE. CONCLUSION: Overall, the BE and the encapsulated BE types tested have antioxidative activity under the studied assay conditions in terms of the prevention of oxidative DNA damage, the reduction of intracellular ROS and the enhancement of cellular tGSH.

Elastometry of deflated capsules: elastic moduli from shape and wrinkle analysis.

Elastic capsules, prepared from droplets or bubbles attached to a capillary (as in a pendant drop tensiometer), can be deflated by suction through the capillary. We study this deflation and show that a combined analysis of the shape and wrinkling characteristics enables us to determine the elastic properties in situ. Shape contours are analyzed and fitted using shape equations derived from nonlinear membrane-shell theory to give the elastic modulus, Poisson ratio and stress distribution of the membrane. We include wrinkles, which generically form upon deflation, within the shape analysis. Measuring the wavelength of wrinkles and using the calculated stress distribution gives the bending stiffness of the membrane. We compare this method with previous approaches using the Laplace-Young equation and illustrate the method on two very different capsule materials: polymerized octadecyltrichlorosilane (OTS) capsules and hydrophobin (HFBII) coated bubbles. Our results are in agreement with the available rheological data. For hydrophobin coated bubbles, the method reveals an interesting nonlinear behavior consistent with the hydrophobin molecules having a rigid core surrounded by a softer shell.

Formation of iron containing aggregates at the liquid-air interface.

The early stages of the formation of inorganic aggregates, composed of iron compounds at the solution-air interface, were investigated in situ. The properties of the solution-air interface were changed by using different Langmuir layers. In order to get insight into the evolution of the sample system in situ, the processes were studied by X-ray scattering and spectroscopy techniques. The formation of aggregates was detected under cationic as well as under anionic Langmuir layers. The observed compounds lack long range order which indicates the formation of amorphous structures. This is supported by extended X-ray absorption fine structure measurements showing only minor order in the formed aggregates.

Effect of microformulation on the bioactivity of an anthocyanin-rich bilberry pomace extract ( Vaccinium myrtillus L.) in vitro.

In cell culture were compared the different release rates of anthocyanins from a bilberry pomace extract encapsulated either in food grade whey protein-based matrix capsules (WPC) or in pectin amid-based hollow spherical capsules (PHS). The impact of the formulations on typical anthocyanin-associated biological end points such as inhibition of the epidermal growth factor receptor (EGFR) and suppression of cell growth in HT29 colon carcinoma cells was assessed. The purpose was to find whether the release rates are sufficient to maintain biological activity and whether encapsulation affected EGFR inhibitory and growth suppressive properties of the extract. Even though anthocyanin release from extract-loaded capsules was proven under cell culture conditions, the inhibitory potential toward the EGFR was diminished. However, nonencapsulated extract as well as both extract-loaded encapsulation systems diminished the growth of HT29 cells to a comparable extent. The loss of EGFR inhibitory properties by encapsulation despite anthocyanin release indicates substantial contribution of other further constituents not monitored so far. Taken together, both applied encapsulation strategies allowed anthocyanin release and maintained biological activity with respect to growth inhibitory properties. However, the loss of EGFR inhibitory effects emphasizes the need for biological profiling to estimate process-induced changes of plant constituent's beneficial potencies.

Silver-doped calcium phosphate nanoparticles: synthesis, characterization, and toxic effects toward mammalian and prokaryotic cells.

Spherical silver-doped calcium phosphate nanoparticles were synthesized in a co-precipitation route from calcium nitrate/silver nitrate and ammonium phosphate in a continuous process and colloidally stabilized by carboxymethyl cellulose. Nanoparticles with 0.39 wt% silver content and a diameter of about 50-60 nm were obtained. The toxic effects toward mammalian and prokaryotic cells were determined by viability tests and determination of the minimal inhibitory and minimal bactericidal concentrations (MIC and MBC). Three mammalian cells lines, i.e. human mesenchymal stem cells (hMSC) and blood peripheral mononuclear cells (PBMC, monocytes and T-lymphocytes), and two prokaryotic strains, i.e. Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) were used. Silver-doped calcium phosphate nanoparticles and silver acetate showed similar effect toward mammalian and prokaryotic cells with toxic silver concentrations in the range of 1-3 µg mL(-1).

Characterizing permeability and stability of microcapsules for controlled drug delivery by dynamic NMR microscopy.

Microscopic capsules made from polysaccharides are used as carriers for drugs and food additives. Here, we use NMR microscopy to assess the permeability of capsule membranes and their stability under different environmental conditions. The results allow us to determine the suitability of different capsules for controlled drug delivery. As a measure of the membrane permeability, we monitor the diffusion of paramagnetic molecules into the microcapsules by dynamic NMR microimaging. We obtained the diffusion coefficients of the probe molecules in the membranes and in the capsule core by comparing the measured time dependent concentration maps with numerical solutions of the diffusion equation. The results reveal that external coatings strongly decrease the permeability of the capsules. In addition, we also visualized that the capsules are stable under gastric conditions but dissolve under simulated colonic conditions, as required for targeted drug delivery. Depending on the capsule, the timescales for these processes range from 1 to 28 h.