Microencapsulation

Microencapsulation brings together all the technologies used to prepare individualized microparticles, consisting of a coating material containing an active ingredient.

Microparticles are between 1 μm and 1 mm in size, and typically contain between 5 and 90% (by mass) of active ingredient. Active ingredients come from a wide variety of sources: active pharmaceutical ingredients, active cosmetic ingredients, food additives, phytosanitary products, perfume essences, micro-organisms, cells, or even chemical reaction catalysts... The coating materials are polymers of natural or synthetic origin, or lipids. The resulting microparticles have two types of morphology:

• or a microcapsule, i.e. a reservoir particle comprising a core of liquid (more or less viscous) or solid active ingredient, surrounded by a continuous solid membrane of coating material;

• or a microsphere, i.e. a particle made up of a continuous macromolecular or lipid network forming a matrix in which the active ingredient is finely dispersed, in the form of molecules, fine solid particles or solution droplets.

From an industrial standpoint, microencapsulation is used to meet the following objectives:

• ensure the protection, compatibility and stabilization of an active ingredient in a formulation;

• create a suitable layout ;

• improve product presentation ;

• masking a taste or smell ;

• modify and control the release profile of an active ingredient to obtain, for example, a prolonged or triggered effect.

This article does not cover molecular encapsulation (cyclodextrins, etc.), soft phases (micelles, liposomes, spherulites, microemulsions, emulsions, etc.) or nanotechnologies.