|
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:
- 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.
- 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.
- 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.
The following images related to this document are available:
Photo images
[pr07007t1.jpg]
|
