Microencapsulation

from Wikipedia, the free encyclopedia

Microencapsulation is a technique with which small portions of solid, liquid or gaseous substances are surrounded with a shell and thus immobilized . Microencapsulation is thus a form of inclusion immobilization . There are many areas of application for microencapsulation: in chemistry , in biotechnology , in pharmacy , in food technology , in cosmetics , in electronics and in environmental technology . Basically, microencapsulation is understood to mean the embedding of at least one substance (active ingredient) with the help of at least a second one (shell material). The former can often not be used directly for various reasons (solubility, reactivity, stability, etc.), or certain effects should be achieved through microencapsulation (e.g. release curves for controlled release, unique selling points, etc.).

  • Matrix encapsulation: Here the active component (s) is mixed homogeneously with the shell component ("matrix") and a particle is created in which the active component (s) is evenly distributed. The release usually determines either the diffusion of the active component (s) into the environment or the rate of degradation of the matrix
  • Core-shell encapsulation: The active substances (“core”) are encased with a shell material. The result is a real capsule with one or more shells, e.g. B. a polymersome . The shell rupture usually produces a complete release of the core material in a short time (“burst”). However, it is also possible to produce an extremely slow release by choosing the right shell

The microencapsulation offers the possibilities:

  • convert liquid substances into powder
  • encapsulate volatile substances
  • Substances before the reaction z. B. protect with air, light or liquids
  • Release active substances within a certain period of time (e.g. medication)
  • Fix poisons
  • Keep reactive substances separate from each other
  • improve the tolerability of drugs
  • improve physical properties of powders
  • Change the electrostatic properties of substances

The first industrial application was a carbonless paper based on a patent from the NCR company from 1953. It was launched in the USA by the Appleton company in 1954. There are now a number of companies on the market that offer commercial microencapsulation using different processes such as dropletization, Emulsion processes, spray processes and the like v. m. to offer.

Procedure

Dropping process When a vibration is applied to a thin jet of liquid (with solution, sol, suspension or melt), regular drops are created which can possibly be charged with the help of a high voltage. Due to the physical repulsion of the particles, almost "round drops" are created. These can be cooled (e.g. wax), dried (e.g. sugar) or exposed to chemical reactions in free fall. For systems that do not show internal gelling (e.g. solidified by cooling), binders are usually used. These solidify the drops and can introduce other properties, such as B. separate defined release profiles, additional protection against environmental influences or reactive components from each other (e.g. oxygen from probiotics, etc.).

literature

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