Microencapsulation involves coating tiny particles or droplets of active ingredients with a thin polymeric film. There are two main types: microcapsules, which have a reservoir structure, and microspheres, which have a matrix structure. Various methods can be used for microencapsulation including pan coating, spray drying, solvent evaporation, coacervation, and centrifugal extrusion. The choice of coating material and method depends on the properties of the core ingredient and desired release characteristics. Microencapsulation provides benefits such as masking tastes, sustained release of ingredients, and protection from moisture, oxygen, and light.

1. MICROENCAPSULATION

2. INTRODUCTION TO
MICROENCAPSULATION
2
▶ Microencapsulation is defined as the application of a
thin polymeric coating to individual core materials (tiny
particles or droplets of liquids and dispersions) that
have an particle size range from 1-1000 μm to give small
capsules with many useful properties.
▶ Generally, capsules can be classified according to their
size: macrocapsules (>1,000 µm), microcapsules (1 to
1,000 µm),and nanocapsules(<1 µm).

3. INTRODUCTION TO
MICROENCAPSULATION
3
▶ Microspheres: micrometric matrix systems.
▶ Microencapsulation is a process by which very tiny
droplets or particles of liquid or solid material are
surrounded or coated with a continuous film of polymeric
material.
▶ Microencapsulated products (microparticles or
microcapsules) are small entities that have an active
agent known as the core material surrounded by a shell
known as the coating material or embedded in a matrix
structure.
▶ Microcapsules: micrometric reservoir systems

4. .
Drug Core
Polymer Coat
= Polymer Matrix
} = Entrapped Drug
MICROCAPSULES MICROSPHERES
•According to some authors, microspheres are essentially spherical
in shape, whereas, microcapsules may be spherical or non-spherical
in shape.
•Also, some authors classify microparticles, either microcapsules
or microspheres, as the same: ‘microcapsules’.

5. INTRODUCTION TO
MICROENCAPSULATION
▶ In terms of their shape and construction, capsules can be divided
into two groups: microcapsules and microspheres. Microcapsules
are particles consisting of an inner core, substantially central,
containing the active substance, which is covered with a polymer
layer constituting the capsule membrane.
▶ However, microspheres are matrix systems in which the core is
uniformly dispersed and/or dissolved in a polymer network.
5

6. COMPOSITION OF
MICROCAPSULE
▶ Core Materials: The ingredients to be coated are referred to as
the core, internal phase (IP), encapsulate, or fill, whereas
terms applied to the coating of the microcapsules include the
wall, shell, external phase or membrane.
▶ All three states i.e., solid, liquid, and gases, may be
encapsulated and affect the size and shape of the capsules.
▶ If core material is a solid or a crystalline material, the
resultant capsule may be irregularly shaped. However, if the
core material is a liquid, the resultant capsule may be
spherical, containing a single droplet of encapsulate. 6

7. COMPOSITION OF
MICROCAPSULE
▶ Coating Materials/Wall Materials/Polymer: The correct choice
of the wall material/polymer is very important because it
influences the encapsulation efficiency and stability of the
microcapsule.
▶ The polymer should be capable of forming a film that is
cohesive with the core material.
▶ It should be chemically compatible, non-reactive with the core
material, and provide the desired coating properties such as
strength, flexibility, impermeability, optical properties, and
stability. 7

8. COMPOSITION OF
MICROCAPSULE
▶ Generally, hydrophilic polymers, hydrophobic polymers, or a
combination of both are used for the microencapsulation
process.
▶ A number of coating materials have been used successfully;
examples of these include gelatin, polyvinyl
ethylcellulose, cellulose acetate phthalate, and
alcohol,
styrene-
maleic anhydride.
▶ The film thickness can be varied considerably depending on
the surface area of the material to be coated and other
physical characteristics of the system. 8

9. COMPOSITION OF
MICROCAPSULE
9
Water-soluble
Water-
insoluble
Waxes and
resins
Enteric
Gelatin
Starch
Hydroxyethylcell
ulose
Polyvinyl
pyrrolidone
Ethyl
Cellulose
Polyamide
Polymethacry
late
Polyethylene
Paraffin
Stearic acid
Beeswax
Stearyl alcohol
Shellac
Zein
Cellulose acetate
phthalate
Examples of coating polymers

10. ADVANTAGES/ APPLICATIONS
OF MICROENCAPSULATION
the incompatibility between drugs.
▶ The main advantage of microencapsulation is to attain the
sustained or prolonged release of the drug.
▶ This technique has been widely used for masking the taste and
odor of many drugs to improve patient compliance.
▶ This technique can be used for converting liquid drugs into a
free-flowing powder.
▶ The drugs which are sensitive to moisture light and oxygen can
be protected by microencapsulation.
▶ The microencapsulation technique is also helpful to prevent
10

11. ADVANTAGES OF
MICROENCAPSULATION
11
▶ The drugs, which are volatile in nature and vaporize at room
temperature, can be prevented by microencapsulation.
▶ Microencapsulation of drugs helps to reduce toxicity and GI
irritation.
▶ Microencapsulation can be done to change the site of
absorption. This application has been useful for those drugs
which have toxicity at lower pH.
▶ Microencapsulation of vitamin A palmitate provides enhanced
stability by preventing it from oxidation.

12. DISADVANTAGES OF
MICROENCAPSULATION
12
▶ It is very difficult to achieve a continuous and uniform film.
▶ There may be a possibility of cross-reaction between core and
coating material.
▶ The Shelf life of hygroscopic drugs is may get reduced by
microencapsulation.
▶ The microencapsulation technique leads to more production
costs.
▶ The microencapsulation technique requires more skill and
knowledge.

13. METHODS OF
MICROENCAPSULATION
13
▶ Polymerization process
▶ Physical Methods
▶ Air-suspension method
▶ Coacervation method
▶ Centrifugal extrusion method
▶ Pan coating method
▶ Sprays drying - Spray congealing method
▶ Single emulsion method
▶ Chemical Methods
▶ Solvent Evaporation method

14. Air suspension method
▶ Principle: A basic principle of
the method is spray coating the
air suspended particles with a
coating material.
▶ Construction: The apparatus
consists of a coating chamber, in
which particles are suspended
on an upward-moving air stream
(heated or not) as indicated in
the figure. The inner design of
the chamber ensures the
14
circulating flow of particles.

15. Air suspension method
▶ Working: At the base of the
the pneumatic or
nozzle has been
chamber
,
hydraulic
placed, which sprays the
coating material (i.e. polymer).
When particles pass through the
coating area, it gains more and
more coating material, thus by
controlling
movement of
the circulating
a particle, the
desired coating thickness can be
achieved. The upward stream
can also be used to dry the
15
particles by making it hot.

16. Air suspension method
16
Factors that can affect the encapsulation process and the
thickness of the coating.
▶ Properties of core material (i.e. particle): Density, surface
area, melting point, solubility, flowability
▶ Properties of coating material: Concentration, melting
point (if not a solution), amount of coating material
▶ Process Variables: Coating material application rate, the
volume of air, the inlet temperature of the air.

17. Air suspension method
17
Advantages of Air Suspension Method:
▶ Low-cost process
▶ It allows specific capsule
porosities into the product
size distribution and low
Disadvantages of Air Suspension Method:
▶ Degradation of highly temperature-sensitive compounds

18. Coacervation Method
(Coacervation – Phase Separation)
formation of a coacervate phase via anion–cation interactions.
▶ Coacervation is the macromolecular aggregation process brought
about by partial desolvation of fully solvated macromolecules.
▶ Simple coacervation processes: It includes a simple coacervation
process in which microencapsulation is carried out by using
water as the solvent phase and a water-soluble polymer as the
coating material. Coacervation is induced by the addition of a
soluble salt or alcohol, change in temperature, or change in pH.
▶ Complex coacervation: In this method, an oppositely charged
polymer is added to the polymer solution leading to the
18

19. Coacervation Method
(Coacervation – Phase Separation)
that
The coacervation process contains three main steps
should be carried out under continuous agitation.
Step 1: Formation of three immiscible chemical phases
Step 2: Deposition of coating
Step 3: Rigidation of coating
19

20. Coacervation Method
(Coacervation – Phase Separation)
20
Step 1: Formation of three immiscible chemical phases
1) Liquid manufacturing vehicle phase
2) Core material phase
3) Coating material phase.
The coating material solution is prepared using a liquid
manufacturing vehicle phase as a solvent, then core material is
dispersed in that solution.

21. Coacervation Method
(Coacervation – Phase Separation)
Step 3: Rigidation of coating
It can be achieved by thermal, cross-linking, or non-solvent
addition techniques.
21
Step 2: Deposition of coating
It is achieved by controlled, physical mixing of coating material
(in liquid state) and core material in the liquid manufacturing
vehicle. The coating material adsorbs on the surface of the
core material.

22. Coacervation Method
(Coacervation – Phase Separation)
Step 3: Rigidation of coating
It can be achieved by thermal, cross-linking, or non-solvent
addition techniques.
22
Step 2: Deposition of coating
It is achieved by controlled, physical mixing of coating material
(in liquid state) and core material in the liquid manufacturing
vehicle. The coating material adsorbs on the surface of the
core material.

23. Coacervation Method
(Coacervation – Phase Separation)
▶ Thermal change: When the temperature of the mixture is
reduced at a definite rate, the coating material phase from the
deposited coating around the core material loses solvent (i.e.
liquid manufacturing vehicle phase) and hence rigidization or
solidification of coating material around microcapsule occurs.
▶ Non-solvent addition: A liquid that is non-solvent for the given
coating polymer can be added to the polymer solution to induce
phase separation. The resulting immiscible liquid coating
polymer can be utilized to form a coat around the core
material. The microencapsulated particles can be centrifuged
and separated from the vehicle phase.
▶ Cross-linking (Polymer addition): When any other polymer
having a solubility in the Liquid manufacturing vehicle phase is
added to the mixture, the polymer that has more strongly
adsorbed to the surface to the core material (normally earlier
selected coating material phase) becomes the coating
23 material
and solidifies.

24. Coacervation Method
(Coacervation – Phase Separation)
Advantages of Coacervation method:
can be used to encapsulate heat-sensitive
as the procedure is carried out at room
▶ Coacervation
ingredients
temperature.
Disadvantages of Coacervation method:
▶ Toxic chemical agents are used
▶ The complex coacervates are highly unstable
▶ There are residual solvents and coacervating agents on the
capsules surfaces
▶ Spheres obtained by the technique are of a low size range
▶ An expensive and complex method 24

25. Centrifugal extrusion method
When the two-liquid column emerges
from the nozzle, it spontaneously breaks
up into a stream of small droplets with
liquid cores surrounded by liquid coats.
coating or shell material gets solidify
Formation of Microcapsule
25
Centrifugal extrusion process requires two immiscible liquids that are
pumped into a spinning two-fluid nozzle.
The core liquid is fed into the center
fluid channel and the coating or shell
liquid is fed into the peripheral fluid
channel.

26. Centrifugal extrusion method
26
▶ The coating or shell material can solidify by various means.
▶ If coating material is a melt it can be rapidly cooled as the
droplets fall away from the nozzle.
▶ If the coating material is formed in a solution form the solvent
can be evaporated by applying heat and forming a solid coat.
▶ Alternatively, the droplets may fall into a gelling bath where
the aqueous shell is converted to a gel-like capsule. The
method of solidification depends on the properties of the
polymer used as shell material.

27. Centrifugal extrusion method
27
Advantages of Centrifugal extrusion method:
▶ The material is totally surrounded by the wall material
▶ Any residual core is washed from the outside
▶ It is a relatively low-temperature entrapping method
Disadvantages of Centrifugal extrusion method:
▶ The capsule must be separated from the liquid bath and dried;
▶ It is difficult to obtain capsules in extremely viscous carrier
material melts

28. Pan Coating Method
▶ The particles are tumbled in a pan or other device while
the coating material is applied slowly.
28

29. Pan Coating Method
29
The particles are tumbled in
a pan (solid particles greater
than 600 microns in size)
The coating is applied as a
solution or as an atomized
spray to the desired solid core
material in the coating pan.
Warm air is passed over the
coated materials to remove
the coating solvent

30. SPRAYS DRYING - SPRAY
CONGEALING METHOD
30
Spray drying and spray congealing processes are similar in that
both involve dispersion of the core material in a liquefied
coating substance and spraying or introducing the core-coating
mixture into some environmental condition, whereby,
relatively rapid solidification and formation of the coating is
affected.

31. SPRAYS DRYING - SPRAY
CONGEALING METHOD
31
Spray drying (Spray – aqueous solution, Hot air)
and spray congealing (Spray – Hot melt, Cold air)

32. SPRAYS DRYING - SPRAY
CONGEALING METHOD
32
▶ The principal difference between the two methods is the
means by which coating solidification is accomplished.
▶ Coating solidification in the case of spray drying is effected by
rapid evaporation of a solvent in which the coating material is
dissolved.
▶ While in spray congealing (cooling) coating solidification is
accomplished by thermally congealing a molten coating
material or by solidifying a dissolved coating by introducing
the coating - core material mixture into a non-solvent.

33. SPRAYS DRYING - SPRAY
CONGEALING METHOD
33
Advantages of Spray drying method:
▶ Low process cost
▶ Wide choice of coating material
▶ Good encapsulation efficiency
▶ Good stability of the finished product
▶ Possibility of large-scale production in continuous mode
Disadvantages of Spray drying method:
▶ It can degrade highly temperature-sensitive compounds
▶ Control of the particle size is difficult
▶ Yields for small batches are moderate

34. SPRAYS DRYING - SPRAY
CONGEALING METHOD
34
Advantages of Spray congealing method:
▶ Temperature-sensitive compounds can be encapsulated
Disadvantages of Spray congealing method:
▶ Control of the particle size is difficult
▶ Yields for small batches are moderate
▶ Special handling and storage conditions can be required

35. Single Emulsion Method
resulting in the formation of compact micro particles.35
The solvent in the emulsion is removed by either evaporation
at elevated temperatures
The polymer is dissolved in a water-immiscible, volatile
organic solvent such as dichloromethane and
the drug is dissolved or suspended in the polymer solution.
The resulting mixture is emulsified in a large volume of water
in the presence of an emulsifier.

36. Single Emulsion method
Advantages of Single Emulsion method:
▶ Polar, non-polar (apolar), and amphiphilic can be incorporated
▶ Emulsions can either be used directly in their “wet” state
Disadvantages of Single Emulsion method:
▶ Instable when exposed to environmental stresses, such as
heating, drying, etc
▶ A limited number of emulsifiers that can be used
Applications Single Emulsion method
▶ This method has been primarily used to encapsulate
hydrophobic drugs through the oil-in-water (o/w) emulsification
process.
▶ In an attempt to encapsulate hydrophilic drugs (e.g. Peptides
and proteins), an oil-in-oil (o/o) emulsification method 3
i6
s used.

37. Solvent Evaporation Method
The mixture is heated (if necessary) to evaporate the solvent of the
polymer
Once all the solvent of the polymer is evaporated, the liquid vehicle
temperature is reduced to ambient temperature (if required) with
continued agitation
if the core material is dispersed in the polymer solution, polymer shrinks
around the core and if the core material is dissolved in the coa37ting polymer
solution, a matrix - type microcapsule is formed.
A core material is dissolved or dispersed in the coating polymer solution.
The coating material is dissolved in a volatile solvent, which is immiscible
with the liquid manufacturing vehicle phase and

38. Polymerization Process
38
Polymerization has the following three types:
▶ In situ polymerization:
▶ Interfacial polymerization
▶ Matrix polymerization

39. Polymerization Process
39
In situ polymerization:
the direct
out on the
▶ In certain microencapsulation processes,
polymerization of a single monomer is carried
particle surface
▶ e.g. Cellulose fibers are encapsulated in polyethylene while
immersed in dry toluene.
▶ The usual deposition rate is about 0.5μm/min.
▶ Coating thickness ranges from 0.2 to 75μm.
▶ The coating is uniform, even over sharp projections.

40. Polymerization Process
40
Interfacial polymerization:
interface and
two reactants in a
react
▶ In interfacial polymerization, the
polycondensation process meet at an
rapidly.
▶ Under proper conditions, thin flexible walls form rapidly at the
interface.
▶ Condensed polymer walls form instantaneously at the interface
of the emulsion droplets.

41. Polymerization Process
41
phase.
Matrix polymerization:
▶ In the number of processes a core material is embedded in a
polymeric matrix during the formation of the particles.
▶ A simple example of this type is spray-drying, in which the
particle is formed by evaporation of the solvent from the matrix
material.
▶ However, the solidification of the matrix can also be done by a
chemical change.
▶ Using this phenomenon prepares microcapsules containing
protein by incorporating the protein in the aqueous diamine

42. Polymerization Process
42
Advantages of polymerization process:
▶ Micro-nanocapsules with narrow size distribution can be
obtained
Disadvantages of polymerization process :
▶ Difficult control of the capsule formation (polymerization)