5 research outputs found
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
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
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
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
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