[show abstract][hide abstract] ABSTRACT: This paper describes the results of the round robin experiment “Bead production technologies” carried out during the COST
840 action “Bioencapsulation Innovation and Technologies” within the 5th Framework Program of the European Community. In this
round robin experiment, calcium alginate hydrogel beads with the diameter of (800 ± 100) μm were produced by the most common
bead production technologies using 0.5–4 mass % sodium alginate solutions as starting material. Dynamic viscosity of the alginate
solutions ranged from less than 50 mPa s up to more than 10000 mPa s. With the coaxial air-flow and electrostatic enhanced
dropping technologies as well as with the JetCutter technology in the soft-landing mode, beads were produced from all alginate
solutions, whereas the vibration technology was not capable to process the high-viscosity 3 % and 4 % alginate solutions.
Spherical beads were generated by the electrostatic and the JetCutter technologies. Slightly deformed beads were obtained
from high-viscosity alginate solutions using the coaxial airflow and from the 0.5 % and 2 % alginate solutions using the vibration
technology. The rate of bead production using the JetCutter was about 10 times higher than with the vibration technology and
more than 10000 times higher than with the coaxial air-flow and electrostatic technology.
Chemical Papers- Slovak Academy of Sciences 04/2012; 62(4):364-374. · 0.88 Impact Factor
[show abstract][hide abstract] ABSTRACT: Melt dispersion technique was investigated for carnauba wax microparticles production. Microbeads with spherical shape and
narrow size distribution were produced. The main objective of this study was to investigate the effect of significant process
variables (initial wax concentration, stirring speed, stirring time, and surfactants) on sphericity, size distribution, and
morphological properties of wax microparticles. Optimal conditions were evaluated on the basis of particle size distribution
and visual analysis. Surface morphology of microparticles was characterized by scanning electron microscopy (SEM). Effects
of process conditions on the size distribution of particles were evaluated by sieve analysis. Main purpose of these investigations
was to apply optimized parameters to aroma encapsulation for their use in food and feed industry.
Keywordsmelt dispersion–carnauba wax–surfactants–microparticles
Chemical Papers- Slovak Academy of Sciences 04/2012; 65(2):213-220. · 0.88 Impact Factor
[show abstract][hide abstract] ABSTRACT: Membrane interactions of liposomes of ternary phospholipid/cholesterol bilayers are investigated. These interactions lead to discoidal deformations and regular aggregations and are strongly enhanced by the presence of mistletoe lectin (ML), a RIP II type protein. The encapsulation of ML into liposomal nanocapsules is studied with a systematic variation of the lipid composition to monitor its effect on the physical properties: entrapment, mean size, morphology, and stability. Extrusion of multilamellar vesicles through filters 80 nm pore size was used for the generation of liposomes. The mean sizes of liposomes ranged between 120 and 200 nm in diameter with narrow size distributions. The increase in flow rate with pressure for three dioleoylphosphatidylcholine (DOPC)/cholesterol (Chol)/dipalmitoylphosphatidylcholine (DPPC) lipid mixtures was linear and allowed to extrapolate to the minimum burst pressure of the liposomal bilayers. From the minimum pressures P(min), the bilayer lysis tensions gamma(l) were determined. The increase in P(min) and gamma(l) with an increasing content of a saturated phosopholipid (DPPC) indicates that DPPC increases the mechanical strength of lipid bilayers. Apparently, DPPC, like cholesterol, leads to a less compressible surface and a more cohesive membrane. After preparation, vesicle solutions were purified by gel permeation chromatography to separate encapsulated ML from free ML in the extravesicular solution. Purified liposomes were then characterized. The content of entrapped and adsorbed ML was measured using ELISA. Repetitive freezing/thawing cycles prior to extrusion significantly increased ML uptake. On the contrary, adsorption was not affected neither by lipid composition, nor concentration and preparation. Differences in experimental encapsulation efficiency only reflect the differences in the mean vesicle sizes of the different samples as is revealed by a comparison to a theoretical estimate. Cryo-transmission electron microscopy (Cryo-TEM) images show that beside spherical, single-walled liposomes, there is a considerable fraction of discoidally deformed vesicles. Based on our results and those found in the literature, we speculate that the flattening of the vesicles is a consequence of lipid phase separation and the formation of condensed complexes and areas of different bending elasticities. This phenomenon eventually leads to agglomeration of deformed liposomal structures, becoming more pronounced with the increase in the relative amount of saturated fatty acids, presumably caused by hydrophobic interaction. For the same lipid mixture aggregation correlated linearly with the ML content. Finally, tested liposomal samples were kept at 4 degrees C to examine their stability. Only slight fluctuations in diameter and the increase in polydispersity after 3 weeks of storage occurred, with no statistically significant evidence of drug leakage during a time period of 12 days, illustrating physical stability of liposomes.
[show abstract][hide abstract] ABSTRACT: The process of electrostatic extrusion as a method for cell immobilization was investigated that could be used for potential applications in medicine. An attempt was made to assess the effects of cell addition and polymer concentration on the overall entrapment procedure, ie, on each stage of immobilization: polymer-cell suspension rheological characteristics, electrostatic extrusion process, and the process ofgelation. The findings should contribute to a better understanding of polymer-cell interactions, which could be crucial in possible medical treatments. Alginate-yeast was used as a model system for carrier-cells. The electrostatic extrusion was considered as a complex two-phase flow system and the effects of cell and alginate concentrations on the resulting microbead size and uniformity were assessed. Under investigated conditions, microbeads 50-600 microm in diameter were produced and the increase in both alginate and cell concentrations resulted in larger microbeads with higher standard deviations in size. We attempted to rationalize the findings by rheological characterization of the cell-alginate suspensions. Rheological characterization revealed non-Newtonian, pseudoplastic behavior of cell-alginate suspensions with higher viscosities at higher alginate concentrations. However, the presence of cells even at high concentrations (5x10(8) and 1x10(9) cells/mL) did not significantly affect the rheological properties of Na-alginate solution. Lastly, we investigated the kinetics of alginate gelation with respect to the quantity of Ca2+ ions and cell presence. The gelation kinetics were examined under conditions of limited supply with Ca2+ ions, which can be essential for immobilization of highly sensitive mammalian cells that require minimal exposure to CaCl2 solution. The molar ratio of G units to Ca2+ ions of 3.8:1 provided complete crosslinking, while the increase in alginate concentration resulted in prolonged gelation times but higher strength of the resulting gel. The cell presence decreased the rate of network formation as well as the strength of the obtained Ca-alginate hydrogel.
International Journal of Nanomedicine 02/2006; 1(2):163-71. · 3.46 Impact Factor