Internal Gelation Method Research Articles

Production of alginate microspheres by internal gelation using an emulsification method.

Alginate is a natural polysaccharide found in brown algae. Alginates are widely used in the food and pharmaceutical industries and have been employed as a matrix for the entrapment of drugs, macromolecules and biological cells. Alginate microspheres can be produced by the external or internal gelation method using calcium salts. The addition of calcium chloride solution in the final phase of production of microspheres by external gelation method using an emulsification technique causes the disruption of the equilibrium of the system being stirred, resulting in a significant degree of clumping of microspheres. Therefore, in this study, production of alginate microspheres by the internal gelation method using a modified emulsification technique was explored. The influence of calcium salt, added in varying amounts and at different stages, on the morphology of the microspheres was investigated. The effects of other hardening agents and different drying methods were also studied.

Preparation of Porous Alumina Microspheres by Internal Gelation Method

A new method based on sol-gel technique of internal gelation has been described for the production of porous alumina microspheres of controlled size in the range 200 to 1000 μm. Good quality alumina gel spheres were prepared directly from aluminium nitrate solution, avoiding the sol preparation step, by adding urea and hexamethylene tetramine as the gelling agents. The process parameters were optimized to get the product of desired morphology. The quality of the spheres was examined by X-ray diffraction (XRD), thermogravlmetry-differential thermal analysis (TG-DTA), fourier transform infrared spectroscopy (FTIR), surface area and pore-size distribution.

External versus internal source of calcium during the gelation of alginate beads for DNA encapsulation

Alginate gels produced by an external or internal gelation technique were studied so as to determine the optimal bead matrix within which DNA can be immobilized for in vivo application. Alginates were characterized for guluronic/mannuronic acid (G/M) content and average molecular weight using 1H-NMR and LALLS analysis, respectively. Nonhomogeneous calcium, alginate, and DNA distributions were found within gels made by the external gelation method because of the external calcium source used. In contrast, the internal gelation method produces more uniform gels. Sodium was determined to exchange for calcium ions at a ratio of 2:1 and the levels of calcium complexation with alginate appears related to bead strength and integrity. The encapsulation yield of double-stranded DNA was over 97% and 80%, respectively, for beads formed using external and internal calcium gelation methods, regardless of the composition of alginate. Homogeneous gels formed by internal gelation absorbed half as much DNAse as compared with heterogeneous gels formed by external gelation. Testing of bead weight changes during formation, storage, and simulated gastrointestinal (GI) conditions (pH 1.2 and 7.0) showed that high alginate concentration, high G content, and homogeneous gels (internal gelation) result in the lowest bead shrinkage and alginate leakage. These characteristics appear best suited for stabilizing DNA during GI transit.

External versus internal source of calcium during the gelation of alginate beads for DNA encapsulation

Alginate gels produced by an external or internal gelation technique were studied so as to determine the optimal bead matrix within which DNA can be immobilized for in vivo application. Alginates were characterized for guluronic/mannuronic acid (G/M) content and average molecular weight using 1H-NMR and LALLS analysis, respectively. Nonhomogeneous calcium, alginate, and DNA distributions were found within gels made by the external gelation method because of the external calcium source used. In contrast, the internal gelation method produces more uniform gels. Sodium was determined to exchange for calcium ions at a ratio of 2:1 and the levels of calcium complexation with alginate appears related to bead strength and integrity. The encapsulation yield of double-stranded DNA was over 97% and 80%, respectively, for beads formed using external and internal calcium gelation methods, regardless of the composition of alginate. Homogeneous gels formed by internal gelation absorbed half as much DNAse as compared with heterogeneous gels formed by external gelation. Testing of bead weight changes during formation, storage, and simulated gastrointestinal (GI) conditions (pH 1.2 and 7.0) showed that high alginate concentration, high G content, and homogeneous gels (internal gelation) result in the lowest bead shrinkage and alginate leakage. These characteristics appear best suited for stabilizing DNA during GI transit. ©1998 John Wiley & Sons, Inc. Biotechnol Bioeng 57: 438-446, 1998.

State and tendency of developing physical-chemical methods for making actinide microspherical particles

To obtain actinides oxides as microspheres, the internal gelation method is suggested. As a dispersive medium, we propose to use hydrocarbons containing fluorine and having a density of 2000 kg/m3. These substances are chemically inert, fire-proof, non-toxic and resistant to γ-radiolysis. Using a fluorohydrocarbon-containing liquid creates in the gelation column a vertical temperature gradient with minimal temperature in the zone of working solution dispersion and maximal one in the upper part of the column. This article treats the mechanism and model of a drop-forming process to control the process of microspheres formation, in which a working solution is dispersed in a dispersive medium.

Immobilization of yeast cells by internal gelation of alginate

A method for immobilizing yeast cells in alginate particles by internal gelation was investigated. The alginate is gelled in situ by the liberation of Ca ions from insoluble calcium compounds through the pH lowering which accompanies d-glucono-1,5-lactone hydrolysis in the presence of solution. With the internal gelation method gel particles of any shape, and novel types of fermentation reactors, can be prepared. The characteristics of the internally gelled, immobilized cell particles were evaluated using a standardized fermentation procedure. The new gelation method exhibited promising characteristics with respect to fermentation rate and gel strength .

Crystal habit and phase attribution of U(VI) oxides in a gelation process

The effects of key process variables on the product characteristics of urania microspheres prepared by an internal gelation method are determined by studies of the crystal structure and morphology of urania in individual gel microspheres. Three compounds in the system UO 3NH 3H 2O are identified, and their characteristic crystal morphologies are determined. The results show that information obtained in this way provides a sound basis for the attribution of phases, for evaluating process conditions and for optimizing process variables.