When microencapsulating solid particles by polymerization and polycondensation, the polymerization initiator is previously grafted onto the surface of the encapsulated substance.
Crosslinking of polymer chains is carried out by introducing special substances into the system, which, as a result of ion exchange, form bonds between two adjacent chains. In this case, the process proceeds at the phase boundary. It is possible to use oil-in-water systems containing a hydrophilic polymer and, for example, lower aldehydes as crosslinking agents. In this case, the interaction of the polymer with the aldehyde proceeds in the aqueous phase, resulting in the formation of a new phase, deposited on drops of oil, since higher aldehydes dissolve in the non-polar phase.
A modern manufacturer of drugs is constantly developing technologies for producing multicomponent drugs with certain properties, mastering new technologies, the main task of which is to ensure the safety and increase the effectiveness of drugs. One of the most promising methods for controlling the properties of drugs is encapsulation in the shell. It is worth emphasizing that encapsulation technologies have a rich history and are widely used not only in the chemical-pharmaceutical industry, but also in the chemical, food industry, agriculture and other industries. In this chapter, the reader can find an overview of encapsulation technologies, some of which can be used to obtain solid, dosage forms, and others - in the production of soft, liquid and gaseous. Encapsulation (from lat. Capsula - box) - the conclusion of small particles of a solid body, their aggregates (granules) or drops of liquid in a thin enough strong shell or in a matrix with ...
During microencapsulation by extrusion, a thin viscous film of film-forming material is formed on the surface with holes of small diameter, through which the encapsulated substance is pressed. The shell thus formed is then stabilized by cooling or polymerizing the monomers included in its composition. For microencapsulation by extrusion, molding devices are also used, which are two coaxially arranged tubes of different diameters (a pipe-in-pipe device). The encapsulated material is fed into the inner hole of the tube under pressure, and the sheath material is fed into the annulus.
The method of spray drying a dispersion or emulsion of an encapsulated substance containing a polymer and a solvent (both organic and aqueous) consists in dispersing them into a heat-carrier gas stream. As a result of heat and mass transfer, the solvent is removed from the system and the formation of dense particles, the encapsulated substance in which is distributed throughout the volume, and not concentrated in the core of the capsule. The most common groups of substances used for spray drying encapsulation are carbohydrates, including modified and hydrolyzed starches, cellulose derivatives, gums and cyclodextrins; proteins, including whey proteins, casein and gelatin; biopolymers. The type of shell material used affects not only the encapsulation efficiency, but also the morphology of the product particles.