This document discusses various methods of microencapsulation. It describes three main techniques: mechanical, chemical, and physicochemical. The mechanical methods discussed are pan coating and Wurster coating, which use mechanical processes to apply coatings. The chemical methods include polymerization, which forms coatings through chemical reactions. Physicochemical methods use phase separation and coacervation to deposit coatings. Specific processes within each method like emulsion polymerization and temperature-induced coacervation are also outlined. Key processing steps and variables are identified for various microencapsulation techniques.

1. VARIOUS METHODS OF
MICROENCAPSULATION.
PRESENTED BY: KABIR NAJEEB
B.PHARM 2012 -16 (Jamia Hamdard University)
New Delhi, India.

2. Introduction:
• Microencapsulation is a process whereby a
relatively thin coatings are applied on to the
surface of solid particles or droplets of liquids and
dispersions. This coatings are made into a thin
layer of film over the particles to which they are
intended to be applied. A good coating on a
substance is that which can not be differentiated
with an uncoated substance by visualizing with
the naked eye. There are different types of
coatings depending on its intended use on a
material.

3. REASONS FOR COATING
• Taste masking: As in the case of drugs with a
bitter or unpleasant taste.
• Target site: For example as in the case of
enteric coated tablets which are meant to
release their content in the intestine.
• Controlled or sustained release drugs: As in
the case of drugs which intended use is to
release drugs over a prolong period of time at
a specific rate.

4. TECHNIQUES USED IN
MICROENCAPSULATION
There are 3 types of different techniques which
are employed for this purpose. They are as
follows:
• MECHANICAL METHOD
• CHEMICAL METHOD
• PHYSICOCHEMICAL METHOD.

5. MECHANICAL METHOD OF
MICROENCAPSULATION
1. PAN COATING:
• ASSEMBLY:
• PAN: The pan in which the particle to be coated
are poured. It’s usually of different sizes ranging
from 4, 6 or even 36 inches, depending on the
quantity of material to be coated. It’s made
from stainless steel.

6. • SPRAY GUN: It’s a pump which delievers the
coating solution into the pan. Pressure is
required to send the coating solution onto the
core material (material to be coated). Solution
will flow out of the gun depending on its
viscosity. Therefore if a solution is too viscous
then it tends to resist from been properly
spread out of the gun, thus solution should
not be too viscous.

7. • HOT AIR BLOWER PIPE: The core material
becomes moist due to coating solution, thus
the hot air blower pipe helps in drying it. The
air should neither be too hot nor too cold.
• EXHAUST PIPE: To remove the excess heat
that is been generated from the hot air blower
as well as the rotating pan, an exhaust is used
in the construction of a coating pan.

8. • WORKING AND OPERATION OF THE COATING PAN
The core material is filled into the coating pan upto 2/3rd
of the pan, the spray solution filled into the spray gun
which is directed into the mouth of the pan at a height
sufficient to provide even distribution of the spray
solution onto the core. The hot air blower pipe also
directed into the pan at a sufficient height to provide
the core material with adequate air supply to dry the
material. Also an exhaust pipe is connected to the
mouth of the pan so as to evacuate excess heat which
may degrade the coating or the core material. The pan
is then made to rotate at an average speed of 18-40
rpm for a sufficient time to complete the coating.

9. • PROCESSING VARIABLES:
• Speed of the pan should be in such a way that
the core materials are evenly sprayed, it
should neither be too high nor too slow.
• Air supply should not be too high to evaporate
the coating substance and not be too hot to
degrade the coating material as well as the
core material.

10. • The viscosity of the spray solution should not
be too viscous to prevent its flow and get
sprayed onto the core.
• The exhaust pipe should serve the purpose of
removing excess heat out of the pan to avoid
degradation of materials.

11. • MERITS/ADVANTAGES OF COATING PAN
METHOD:
• Operation is easy i.e does not require a
technically sound person.
• Only one person can carry out the general
operation.

12. • DEMERITS/DISADVANTAGES:
• Relatively small amount of materials are
coated at a time.
• Sometimes there is the need for further drying
in the oven
• It’s a traditional means of coating

13. 2. WURSTER/AIR SUSPENTION METHOD
• ASSEMBLY:
• CONTROL PANEL: This comprises of the switches
and buttons for the control and regulation of the
moving parts on the coating chamber.
• COATING CHAMBER: This is the part of wurster
apparatus that carries out the coating processes.
The core materials are fed into this chamber. In
the chamber there is an air distribution plate as
well as nozzle for the application of film coating.

14. • AIR DISTRIBUTION PLATE: This plate carries
out the distribution of air in the chamber. The
plate has many tiny holes which distributes air
as it flows into the chamber, there by
providing for even distribution of air.
• SPRAY NOZZLE: Just like a spray gun, the
nozzle has the ability to release spray solution
based on pressure.

15. • WORKING AND OPERATION OF WURSTER
APPARARUS
• Just as the name sounds air suspension
apparatus, the working of this apparatus
depends on air. The core materials (material to
be coated), are fed into the coating chamber,
in a quantity which is not more than 2/3rd of
the chamber (75% of the chambers capacity).

16. • The control panel is used to set the speed of the air
that flows into the chamber as well as the amount of
coating materials (solution) coming out of the spray
nozzle. After the material have been fed into the
coating chamber and the air as well as the spray nozzle
are set, and the operation began, the materials are
seen suspended in the coating chamber due to the
blowing action of the air, as the coating material oozing
out of the spray nozzle gets them coated randomly.
After sometimes the whole materials gets coated as
well as dry due to the effect of the hot air from the air
distribution plate. The machine is stopped and the
coated materials are taken out.

17. • PROCESSING VARIABLES:
• Density, surface area, melting point, and
flowability of the core materials.
• Viscosity/concentration of the coating
material (solution).
• Volume of air sufficient to suspend the core.
• Amount of coating materials.

18. • MERITS/ADVANTAGES
• Cheap process in comparison to spray dryer
method.
• Fast method of encapsulation.
• One person is required to carry out the
process.
• Method for both micro as well as macro sized
particles encapsulation.

19. • DEMERITS/DISADVANTAGES
• Core materials of micron/submicron can be
encapsulated effectively by this process but
agglomeration into larger particles can occur.
• The size of the particle must be within the
range that the air can suspend.
• More costly than pan coating.

20. • The particle is embedded as in the figure
below:

21. 3. SPRAY DRYER METHOD
• ASSEMBLY:
• FEED TANK/MIXING TANK: The core materials and
the coating solution are mixed together to form
slurry.
• ATOMIZER: It’s at the top of drying chamber
through which the slurry enters into the chamber.
It breaks the slurry into droplets as it spins at the
rate of 3000-50000 rpm (rounds per minute). Here
centrifugal or spinning disc atomizer is been used.

22. • DRYING CHAMBER: This is the largest part of
the spray dryer. It consists of the atomizer, the
adjustable air dispenser. It carries out the
whole process of spray drying.
• AIR HEATER: Supplies the hot air that enters
into the drying chamber.
• ADJUSTABLE AIR DISPENSER: It spreads the air
in the chamber as it comes in contact with the
droplets from the atomizer.

23. • CYCLONE PRODUCT COLLECTION: The
microencapsulated product/powders are
carried by the dry air into the cyclone and thus
final products are collected.
• CHAMBER PRODUCT COLLECTION: Materials
that are not carried into the cyclone by the air
or those that sticks to the wall of the drying
chamber are collected at the bottom of the
drying chamber.

25. • WORKING AND OPERATION OF SPRAY DRYER:
• The core material and the coating materials
are mixed together into a solution or slurry in
the mixing tank/feed tank, and introduced into
the drying chamber. The slurry is then passed
into the drying chamber via the spinning disc
or centrifugal atomizer from the top. At the
same time the dry air is heated by air heater to
high temperature and introduced into the
drying chamber via an air dispenser which is
mounted around the atomizer.

26. • As the slurry enters into the drying chamber, its
broken down into droplets by the spinning disc
atomizer or centrifugal atomizer at 3000-50000
rpm and dispersed into the heating chamber.
Atomization at this point increases liquid surface
area for minimum contact between air and liquid
droplets.
• As the hot air flows in a rotational movement and
thus gets evenly distributed in the whole chamber,
when the hot air is in contact with the liquid mist,
fast evaporation of the solvent begins, as the
solvents evaporates from the droplets surface, solid
particles are formed, which falls to the bottom of
the chamber.

27. • The hot drying gas flows through the spray
drying chamber and carries the product to the
cyclone. The hot drying air is eliminated
through the air outlet into the atmosphere.
Products which do not pass through the
cyclone are collected in the collection
chamber.

28. The set up is shown below:

29. • PROCESSING VARIABLES:
• Quality of the core materials
• Viscosity of the coating materials.
• Balance between speed of atomizer and hot
air.

30. • MERITS/ADVANTAGES:
• The dry particles can be easily controlled.
• Thermo labile products can be spray dried at
relatively high inlet temperatures.
• Short residence time is required.
• Minimum flavor loss as in sweetened particles.
• It ensures high product quality.
• Very fast means of microencapsulation.

31. • DEMERITS/DISAVANTAGES:
• The equipment is very costly.
• Very bulky.
• Requires a technically sound person.
• Cleaning is time consuming.
• A lot of heat is wasted as thermal efficiency is
low.

32. 4. SPRAY CONGEALING:
• This method is same as in the case of spray
dryer, only that in this case the coating
materials are not in the form of solution
instead they are in molten form i.e they can
melt at room temperature. And they are
passed at a temperature of 30-40 degree. And
cool air is passed into the chamber instead of
hot air as in the case of spray dryer.

33. 5.FLUIDIZED BED DRYER:
• This is a system of drying where by particles of
solids are subjected to suspension by passing a
gas onto the bed so the mixture of the duo
behaves like a liquid, they are said to be fluidized.
This method is efficient for drying of granules
because each particle is surrounded by the drying
gas. So in the case of microencapsulation, solid
particles are subjected to fluidization with the
coating materials in the form of gases, thus the
intense mixing between particles and gaseous
(coating) materials, results in uniform conditions
of temperature, composition and particle size
distribution throughout the bed.

34. CHEMICAL METHODS OF
MICROENCAPSULATION
• POLYMERIZATION: This is a process where by
relatively small molecules called monomers combine
chemically to produce a very large chainlike or network
of molecules called POLYMERS. The monomer
molecules may be all alike or they may represent two,
three or more different compounds. Usually at least
100 monomer molecules must be combined to make a
product that has certain unique physical properties
such as elasticity, high tensile strength, or the ability to
form fibres that differentiate polymers from substances
composed of smaller and simpler molecules; often,
many thousands of monomer units are incorporated in
a single molecule of a polymer.

35. • PRINCIPLE OF POLYMERIZATION TECHNIQUE:
In this technique, we use a type chemical reaction
known as PHOTOPOLYMERIZATION REACTION.
Photopolymerization reactions are chain-growth
polymerizations which are initiated by the
absorption of visible or ultraviolet light. The light
may be absorbed either directly by the reactant
monomer (direct photopolymerization), or else by
a photosensitizer which absorbs the light and then
transfers energy to the
monomer. Microencapsulation by this process is
archived when the drug has been enclosed in a
polymer.

36. • SOLUTION POLYMERIZATION:
• In a closed beaker take the core material along
with the monomer.
• Allow the mixture to undergo
photopolymerization by passing UV radiation for
8-10 hours, the UV radiation serves as the
reaction initiator. A stirrer is introduced through a
tiny opening at the top of the beaker. After a hazy
solution develops which means the core material
is enclosed by the coating material in the form of
polymers formed by the reaction of monomers
along with drugs by photopolymerization, thus
microencapsulation is achieved.

37. • EMULSION POLYMERIZATION:
• In this case 2 monomers from organic and
inorganic forms are mixed together to form a
polymer. Polymer is formed at the interphase of
the organic and inorganic layers (oil and water
layers) example of polymer is nylon.
• The core material i.e the drug as well as the
organic phase and inorganic phase (oil and water
monomers) are taken together in a beaker, UV
radiation is used to initiate the polymer formation
with stirring, the polymer is formed at the
interphase with the drug embedded by the
polymer.

38. • PROCESSING VARIABLES:
• Amount of reaction to carry out the process.
• Ratio of drug to monomer.
• Reaction initiator i.e temperature or UV
radiation.

39. PHYSICOCHEMICAL
MICROENCAPSULATION
This method of microencapsulation is carried
out by coacervation-phase separation which
consists of three steps as follows:
1. Formation of 3 immiscible chemical phases.
2. Deposition of coating over the core material.
3. Stabilizing the coating material on the core.

40. STEP 1: FORMATION OF 3 IMMISCIBLE CHEMICAL
PHASES:
• The 3 immiscible chemical phases are: Solvent
(liquid manufacturing vehicle phase), a core
material phase and a coating material phase.
• The 3 phases are formed thus: The core (drug) is
dispersed in the polymer (coating material) which
is containing the solvent (liquid manufacturing
phase). The coating material phase (an immiscible
polymer in a liquid state) is formed by any method
of phase-separation coacervation which includes:
temperature change, by salt addition, by polymer-
polymer interaction.

41. STEP 2: DEPOSITION OF COATING OVER THE
CORE MATERIALS:
• This is achieved by controlled or physical
mixing of core and coating materials (while
liquid). The deposition of polymer over the
core material is easy when the interfacial
energy of the system is low, there by enabling
proper and easy embedding of the core in the
coating material.

42. STEP 3: STABILIZING THE COATING MATERIAL
ON THE CORE:
• The coating material is made to get rigid on
the surface of the core by thermal, cross
linking or desolvation technique.

43. METHODS OF PHASE SEPARATION
COACERVATION
1. TEMPRATURE CHANGE:
• In this method, the solvent along with the polymer is
taking and the temperature is raised to form a solution.
• The solution is allowed to cool and then gradually the
core material is added slowly by continuous stirring
with a stirrer.
• The temperature therefore becomes the dissolubilizing
agent.
• Example: - Solvent: Cyclohexane
• Polymer: Ethyl cellulose
• Drug: Ascorbic acid
• Dessolubilizing agent: Temperature.

44. 2. INCOMPATIBLE POLYMER ADDITION:
• Example: - Polymer: Ethyl cellulose
• Core: Methyl blue
• Solvent: Toluene
• Dissolubilizing agent: Polymethylene.
• The polymer is dissolved in the solvent to form a
solution.
• Polymethylene which is incompatible with the
previous polymer is then added so as to
dissolubilize the polymer i.e ethylcellulose.
• The core i.e drug is the added with stirring using a
stirrer to form acervates.
• Thus the drug is embedded in the polymer.

45. 3. NON SOLVENT ADDITION:
• Example: - Solvent: Methyl ethyl ketone
• Polymer: Cellulose acetate butyrate (CAB)
• Core: Methylscopolamine
• Dissolubilizing agent: Isopropyl alcohol.
• The polymer is dissolved in the solvent to form a
solution.
• Dissolubilizing agent is added drop wise to the
solution.
• The drug is added by stirring continuously.
• Accervates are formed there by embedding the
drugs.
• Hardening of the coated drug by oven drying.

46. 4. BY SALT ADDITION:
• This is based upon emulsion technique.
Sodium sulfate is commonly used.
• Example: - Solvent: oil + water
• Polymer: Gelatin
• Core: Vitamin A ( Fat soluble vitamins A,D,E,K)

47. • Gelatin in water solution (10%) to form a
monophasic solution by heating at 37 degree
and allow it to cool.
• To the solution, add oil with continuous
stirring and thus water in oil emulsion is
formed.
• The core (vitamin A) is added to the solution
by stirring.
• The salt (Sod. sulfate) is added to the solution
which causes the hardening of the solution at
a certain concentration, thus the vitamin gets
embedded.

48. 5. COMPLEX COACERVATION:
• In this method we form a coating on the drug
using two polymers.
• Example: - Coating material: Acacia + gelatin
• Core: Methyl salicylate
• Solvent: Water
• Dissolubilizing agent: Ph/isoelectric point.

49. • Positive and negative charges from acacia and
gelatin will form a complex which will form a
layer on the drug.
• At a particular Ph they both have a neutral
charge, but at ph 4.5 they have an opposite
charge which will make them form a complex by
hardening.
• Core (methyl salicylate) is added by continues
stirring.
• PROCEDURE:
• Gelatin + Acacia + water @ ph 4.5
• Drug is added gradually with continuous stirring
and thus drug gets embedded.