Advantages And Disadvantages Of Internal Gelation

Internal gelation provides a better encapsulant protection from hydrolysis of bioactive compounds when compared to external gelation. The draw back of internal gelation in this process is that it may allow high losses from the microspheres.

For water-soluble drugs, the use of external gelation technique involving alginate polymers using an aqueous cross-linking agent would minimize the entrapment efficiency because the drug gets diffused into the aqueous phase during the curing of the gel beads. Besides, the other drawbacks include the limitation in minimizing the teardrop shape of the microparticles and limitation in minimizing the diameter of the formed microspheres. produced and difficulty in industrial scale-up. The emulsification-internal

Polymers, which are prepared from renewable natural resources, have become increasingly important and are highly preferred due to their ready availability, water solubility, bio degradability, its gel forming ability, bio compatability and their low cost.

Alginate became the most widely used encapsulation matrix for biological materials including mammalian cells, plant cells, yeasts, bacteria, insulin, magnetite, food products and toners. Alginate can form stable reversible gels in the presence of multivalent cations under stable formulation conditions at room temperature. It is inexpensive, widely available as food or medical grade material and biocompatible in nature. Alginate also has several unique properties that made it as the most widely used matrix-forming material for entrapment and/or delivery of a variety of proteins and cells.

Relative to its concentration, almost no spherical particles were formed with sodium alginate concentration below 1.0%, probably due to the lack of enough carboxyl groups for gelation. If the Na alginate concentration is higher the viscosity of the aqueous phase is increased larger droplets with wide distribution can be attained. It is essential to maintain the concentration of alginate with respect to particle shape, its adistribution and particle

Calcium is the main cation employed as it is considered as clinically safe, economical and easily accessible. Structurally, calcium ions are located in electronegative cavities, which were described as an egg-box model in the literature. Ionic interactions between guluronate blocks and calcium ions lead to the formation of a strong thermostable gel with properties that depend largely on the preparation method and characteristics of the