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Tropical Journal of Pharmaceutical Research
Pharmacotherapy Group, Faculty of Pharmacy, University of Benin, Benin City, Nigeria
ISSN: 1596-5996 EISSN: 1596-9827
Vol. 6, Num. 2, 2007, pp. 685-686
Untitled Document

Tropical Journal of Pharmaceutical Research, Vol. 6, No. 2, June 2007, pp. 685-686

Editorial

Life is based on a combination of biochemistry and bioencapsulation

Denis Poncelet

President of the Bioencapsulation Research Group, and Professor, ENITIAA, Rue de la géraudière, BP82225, 44322 Nantes Cedex, France. Email: poncelet@enitiaa-nantes.fr

Code Number: pr07007

A long time ago, it was nothing. Then, a big bang dispersed energy over the universe. Some of this energy compacted to form atoms, which combined to form molecules. The molecules became more and more complex, resulting in biochemistry, but life was still not there.

Somebody, let us call Him God, said, let's try a new thing. Let's put a microcapsule (membrane) around this biochemistry. Then, life started! Biological cells multiplied, and colonized the earth. They organized themselves to give pluricellular organisms, which evolved to finally become an exceptional structure of more than 1012 microcapsules called a human being.

Bioencapsulation essentially mimicks this very ancient process, i.e.

  • immobilizing bioactive material ('actives'), thus avoiding its dispersion in water.
  • protecting it (against pH, oxygen, etc,.
  • controlling mass transfer (exchange with the surrounding).
  • structuring it (change from liquid state to an apparent solid form), and
  • creating new functions (such as ATP production over mitochondrial membrane).

The challenge of bioencapsulation researchers and engineers is to obtain microcapsules presenting powerful properties and functions like biological cells.

The initial microcapsule concept referred to a liquid core surrounded by a membrane; however, biocapsules may take many different forms such as solid beads, hydrogel beads, liposomes, etc. The core could be a solid, a liquid, an emulsion, or a liquid dispersion in a solid matrix. Some companies even develop small capsules integrated inside larger capsules

There are a number of methods (and combinations of methods) for producing microcapsules. One simple approach is to classify them as shown in Table 1 based on the assumption that an encapsulation process comprises of three steps:

  1. Incorporation of the 'actives' in the future core of the capsules; if the core is liquid, the ‘actives’ may be dissolved, dispersed, or emulsified in this liquid. If the core is solid (particles), the ‘actives’may be incorporated by absorption during or after production of the core particles.
  2. Dispersion of the core; either by production of air droplets or liquid dispersion (in the case of a liquid core) or by agitation of a powder and deposition of the coating material on it.
  3. Stabilisation of the capsules; liquid droplets or particles surrounded by a liquid are stabilized by solidifying the external surface (membrane) or the core (beads) via solidification, gellation, polymerization, precipitation, drying or any other physical, physicochemical or chemical process.

Table 1: Classification of the microencapsulation methods

Encapsulation steps

Initially, the core phase is liquid

(solution, melt, …)

Initially, the core is solid (particles, beads …)

1) Incorporation

Dissolution, dispersion or emulsification

of the active ingredient in the core phase

Absorption of the active ingredient during or after production of the particles

2) Dispersion / agitation

Production of droplets in air or liquid

Particles in fluid bed or rotating pan

+ spray coating

Suspension of particles or beads in coating solution

Dripping/

dropping in air or a stabilizing solution

Spraying of fine droplets in air

Emulsion / dispersion of the core in a continuous phase

3) Stabilisation

Solidification

Prilling

Spray cooling

 

Spray coating

 

Drying

Evaporation

 

Spray drying

Solvent evaporation

Spray coating

 

Gelation

Hydrogel beads

Spray chilling

Thermal gelation

 

 

Polymerisation

 

 

Interfacial or in situ polymerisation

 

 

Coacervation

Precipitation

 

 

Simple or complex coacervation

 

 

Molecular interaction

Interfacial coacervation

 

liposome

 

Ionic coating

Biocapsules may be used for many purposes; specifically, in the medical domain, one could cite:

  • Taste and odor masking of unflavored drug

  • Protection of actives against water or oxygen during storage

  • Enhancement of flow properties of powders in tablet production

  • Protection of drug against gastric juice and colon delivery of medicines

  • Formulation of injectable drug form with controlled release profile

  • Targeting of drug to a specific body site (in cancer therapy)

  • Chondrocyte immobilization for bone reconstruction

  • Langerhans islet protection against immune system following implantation for treatment of diabetes.

This is only a short list of potential applications. The domain of applicability is very broad and is likely to expand in the next few years. For additional information, you may connect to the Bioencapsulation Research Group website (http://bioencapsulation.net) where you will find listed relevant books and reviews.

Copyright 2007. Pharmacotherapy Group, Faculty of Pharmacy, University of Benin, Benin City, Nigeria.


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