Silk fibroin (SF) is a protein with many outstanding properties (superior biocompatibility, mechanical strength, etc.) and is often used in many advanced applications (epidermal sensors, tissue ...engineering, etc.). The properties of SF-based biomaterials may additionally be tuned by SF interactions with other (bio)polymers. Being a weak amphoteric polyelectrolyte, SF may form polyelectrolyte complexes (PECs) with other polyelectrolytes of opposite charge, such as poly(acrylic acid) (PAA). PAA is a widely used, biocompatible, synthetic polyanion. Here, we investigate PEC formation between SF and PAA of two different molecular weights (MWs), low and high, using various techniques (turbidimetry, zeta potential measurements, capillary viscometry, and tensiometry). The colloidal properties of SF isolated from
and of PAAs (MW, overlap concentration, the influence of pH on zeta potential, adsorption at air/water interface) were determined to identify conditions for the SF-PAA electrostatic interaction. It was shown that SF-PAA PEC formation takes place at different SF:PAA ratios, at pH 3, for both high and low MW PAA. SF-PAA PEC's properties (phase separation, charge, and surface activity) are influenced by the SF:PAA mass ratio and/or the MW of PAA. The findings on the interactions contribute to the future development of SP-PAA PEC-based films and bioadhesives with tailored properties.
Microencapsulation of bioactive substances is a common strategy for their protection and release rate control. The use of chitosan (Ch) is particularly promising due to its abundance, ...biocompatibility, and interaction with anionic surfactants to form complexes of different characteristics with relevance for use in microcapsule wall design. In this study, Ch/sodium dodecyl sulfate (SDS) microcapsules, without and with cross-linking agent (formaldehyde (FA) or glutaraldehyde (GA)), were obtained by the spray drying of vitamin E loaded oil-in-water emulsion. All of the microcapsules had good stability during the drying process. Depending on the composition, their product yield, moisture content, and encapsulation efficiency varied between 11-34%, 1.14-1.62%, and 94-126%, respectively. SEM and FTIR analysis results indicate that SDS as well as cross-linkers significantly affected the microcapsule wall properties. The profiles of in vitro vitamin E release from the investigated microcapsules fit with the Korsmeyer-Peppas model (r
> 0.9). The chemical structure of the anionic surfactant was found to have a significant effect on the vitamin E release mechanism. Ch/SDS coacervates may build a microcapsule wall without toxic crosslinkers. This enabled the combined diffusion/swelling based release mechanism of the encapsulated lipophilic substance, which can be considered favorable for utilization in food and pharmaceutical products.
Double emulsions are complex liquid dispersion systems in which the droplets of one dispersed liquid are further dispersed in another liquid, producing W/O/W or O/W/O emulsions. W/O/W emulsions are ...the most studied systems because they have great potential application. However, despite all the advantages, that these systems offer, it is very difficult to obtain stable formulations, and this is the reason for their limited practical application. The use of biopolymers to stabilize double emulsions could give rise to pharmaceutical and food applications. Based on previous studies, appropriate concentrations of gelatin and sodium caseinate (NaCAS) were selected to investigate the possibility of stabilization of double W/O/W emulsions by this system, if they are present in the outer aqueous phase. The investigations showed that interactions between gelatin and NaCAS in the outer water phase, as well as the composition of the mixtures of lipohilic emulsifiers used for the primary W/O emulsions preparation, influences the droplets size and sedimentation stability of double emulsions. The most stable emulsions were obtained at a NaCAS concentration when an insoluble coacervate forms (0.5 mass %) and at concentrations higher then this, when soluble negatively charged complexes adsorb at the oil/water interface.
Pumpkin (Cucurbita pepo) seed protein hydrolysate (PSPH) was obtained by enzymatic hydrolysis of pumpkin seed protein isolate using pepsin. Influence of pH (3, 5 and 8) and ionic strength, Ic (0?1 ...mol dm-3), on the adsorption kinetics of PSPH (diffusion rate constant, kdiff, and adsorption rate constant, kads), interfacial pressure (?) and interfacial dilatational properties (dilatational elasticity, E?, and viscosity, E?) of the oil?PSPH solution interfaces was investigated at different PSPH concentrations (c = 0.0014?14 g dm-3). It was found that PSPH adsorbs to the interface at c ? 0.0014 g dm-3, regardless of pH and ionic strength, as evidenced by the increase in interfacial pressure. The kdiff and kads value were found to be the highest at pH 3 and the lowest at pH 5 at the corresponding concentrations. The dilatational properties of the interfaces, which were investigated at different oscillation frequencies, ?, 0.01?0.2 Hz, showed that the E? of the oil?PSPH solution interfaces is much higher than its E?. Moreover, E? increases with increasing PSPH concentration at pH 5 and 8, and with increasing Ic, regardless of the pH, while E? changes only minimally.
Chitosan is a cationic biopolymer, which attracts more and more attention in
recent years, due to its exceptional physical and chemical properties,
expressive biocompatibility and possibilities of ...obtaining from renewable
sources. Formed polymer/surfactant complexes affect changes in the
rheological properties and the final result is the formation of coacervates.
The purpose of this study was to investigate the rheological properties of
aqueous solutions of cationic polyelectrolyte, chitosan and sodium lauryl
ether sulfate (SLES), an anionic surfactant, widely used in the cosmetics
industry. Using the Thermo Haake RS600 rheometer, changes in the rheological
and elastic properties of chitosan and SLES mixtures have been identified,
gained as a result of the interaction of the components. In all examined
samples coefficient of thixotropy was increasing with increase SLES
concentration and achieves a maximum value at the mass ratio chitosan:SLES
1:2, after which it reduces. The oscillatory measurements in mixtures,
performed by amplitude sweep method at low oscillating frequency 1 Hz, show
that the linear viscoelastic region increases with increasing SLES
concentration up to the same chitosan:SLES mass ratio. By monitoring the
changes in the rheological parameters of the mixtures over five days, it was
observed that the viscosity, the coefficient of thixotropy and elasticity
were increasing, indicating that changes in the system occur over a longer
period of time. In that manner, obtained results indicate the possibility of
using rheological methods for a more detailed description of the interaction
in the chitosan/SLES mixtures, important for their application in cosmetics
and pharmaceutical industries.
Water in oil (W/O) emulsions are dispersed systems which have very wide
application as a carriers in the food, pharmaceutical and cosmetic industry
products. The main problem with practical ...application of such systems is
their low stability. The emulsifiers used to stabilize this type of emulsions
are with low hydrophilic-lipophilic balance values. The present work examines
the possibility of the application of mixtures of lipophilic emulsifiers
polyglycerol polyricinoleate (PGPR) and polyglycerol fatty acid esters for
stabilization of W/O emulsions. First of all, the adsorption properties of
the used emulsifiers were examined by tensiometic measurements. Based on
these results, two emulsifiers PGPR and decaglycerol decaoleate (Caprol
10G10O) were selected for the preparation of the emulsions, as well as their
mass ratios and total concentrations. The results of the investigation of the
emulsions properties (dispersion analysis and sedimentation stability) showed
that more stable emulsions can be obtained by decreasing the Caprol 10G10O
mass ratio and increasing the total concentration of emulsifiers.
Contemporary formulations of cosmetic and pharmaceutical emulsions may be
achieved by using combined polymer/surfactant system, which can form
complexes with different structure and physicochemical ...properties. Such
complexation can lead to additional stabilization of the emulsion products.
For these reasons, the main goal of this study was to investigate the
interfacial properties of chitosan/sodium dodecyl sulfate complexes. In order
to understand the stabilization mechanism, the interface of the oil/water
systems that contained mixtures of chitosan and sodium dodecyl sulfate, was
studied by measuring the interfacial tension. Considering the fact that the
properties of the oil phase has influence on the adsorption process, three
different types of oil were investigated: medium-chain triglycerides
(semi-synthetic oil), paraffin oil (mineral oil) and natural oil obtained
from the grape seed. The surface tension measurements at the oil/water
interface, for chitosan water solutions, indicate a poor surface activity of
this biopolymer. Addition of sodium dodecyl sulfate to chitosan solution
causes a significant decrease in the interfacial tension for all investigated
oils. The results of this study are important for understanding the influence
of polymer-surfactant interactions on the properties of the solution and
stability of dispersed systems.
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•Ch/SLES complex was used as emulsion stabilizer.•Vitamin E was encapsulated by spray drying process.•Microcapsules without cross-linking agent had good characteristic.•Ch/SLES ...complex can be used as wall material for the microencapsulation.•Controlled release systems improved the application of vitamin E in cosmetic.
Potential benefit of microencapsulation is its ability to deliver and protect incorporated ingredients such as vitamin E. Microcapsule wall properties can be changed by adding of coss-linking agents that are usually considered toxic for application. The microcapsules were prepared by a spray-drying technique using coacervation method, by depositing the coacervate formed in the mixture of chitosan and sodium lauryl ether sulfate to the oil/water interface. All obtained microcapsules suspensions had slightly lower mean diameter compared to the starting emulsion (6.85 ± 0.213 μm), which shows their good stability during the drying process. The choice and absence of cross-linking agents had influence on kinetics of vitamin E release. Encapsulation efficiency of microcapsules without cross-linking agent was 73.17 ± 0.64 %. This study avoided the use of aldehydes as cross-linking agents and found that chitosan/SLES complex can be used as wall material for the microencapsulation of hydrophobic active molecules in cosmetic industry.
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•The composition of nanoparticles affects their surface charge density.•Addition of GA increases size of Z and Z/R NPs.•Interactions with GA are the most intensive at pH = 4 for both ...Z and Z/R NPs.
The objective of this study was to investigate interactions of zein (Z) and zein/rosin (Z/R) nanoparticles with gum arabic (GA), at different pH. Nanoparticles were firstly prepared by antisolvent precipitation of biopolymers from aqueous ethanol solutions. Nanoparticles suspensions were then dialyzed against water in order to remove ethanol and other impurities, and water suspensions of zein and zein/rosin nanoparticles were obtained. It was shown that composition of nanoparticles affects their surface charge density. Zeta potential of nanoparticles was positive without GA and changed to negative after addition of GA, at all pH tested. SEM analysis proved both Z and Z/R nanoparticles to be spherical and in size around 200 nm. The effect of addition of GA on particle size was determined using dynamic light scattering method. It was found that addition of GA increases size of nanoparticles at pH = 4 and pH = 5.5, from 150 – 220 nm to 250 – 320 nm. However, at pH = 3 it causes aggregation process, and diameter of particles increases up to few micrometres. Isothermal titration calorimetry was used to measure enthalpy changes in reaction between Z or Z/R nanoparticles and GA. Results showed that reaction between GA and Z or Z/R NPs is exothermic at each pH tested, except for Z NPs at pH = 3, where it was endothermic. At presented pHs, Z/R NPs were less charged compared to Z NPs, and their surface get saturated with GA molecules more rapidly. Z NPs showed greater enthalpy change in reaction with GA, compared to Z/R NPs.
Zein, a corn protein, is often used for preparing edible films and coatings. Since zein is insoluble in water, zein films and coatings are usually prepared by spraying or casting its aqueous ethanol ...solutions to a contact surface (Zsol films). However, the use of organic solvents in many food applications is unwanted. In this work, aqueous dispersions of zein nanoparticles were prepared by antisolvent precipitation from 90% v/v aqueous ethanol zein solutions. Zein films were then prepared by casting the dispersions in silicone molds and air–drying at 50 °C (Zdis films). The obtained films were characterized for morphology, FTIR analysis, mechanical, water barrier and optical properties, and were benchmarked against Zsol films. It was found that continuous zein films can be prepared out of aqueous dispersions of zein nanoparticles. Zdis films proved to have grainy morphology and higher surface roughness when compared to Zsol. Surface roughness of Zdis films was decreased when plasticizer was added. Water barrier properties of Zdis films were found to be comparable to Zsol films. No differences in mechanical properties were found between Zsol and Zdis film. Size of zein particles influenced morphology and optical properties of zein dispersion films.
•Continuous zein films were prepared by casting nanoparticle dispersions in water.•Particle size influence morphology and optical properties of zein dispersion films.•Water barrier properties of ZDNP films were found to be comparable to ZS films.
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