Detailed information about Microencapsulation

1. MICROENCAPSULATION
By: Ankita Kanshide
Maratha Mandal’s College of Pharmacy

2. MICROENCAPSULATION
• Microencapsulation is defined as a process of enclosing or enveloping
solids, liquids or even gases with a continuous coating of polymeric
materials yielding microscopic particles for the purposes of providing
environmental protection and controlling the release characteristics.
• The particle size ranges from 1-1000 µm.
• Two general micro morphologies of microparticles are microcapsules
and microspheres.

3. • The term “microcapsule” is used to describe particles in which a drug-
containing core is completely surrounded by a polymer shell.
• While, “microspheres” are defined as microparticles in which the
drug substance is homogenously dispersed in a polymeric matrix.

4. FORMULATION CONSIDERATIONS
1. Core Material:
The material to be coated is known as core material.
It may be liquid or solid or gas.
Liquid core may be dissolved or dispersed material.
Composition of core material:
a. Drug or active constituent
b. Additive like diluents
c. Stabilizers.

5. 2. Coating Material:
Inert substance which coats on core with desired thickness.
Composition of coating:
a. Inert polymer
b. Plasticizer
c. Coloring agent
d. Resins, waxes and lipids
e. Release rate enhancers or retardants.
Example: Gelatin, Ethyl cellulose, cellulose nitrate, Paraffin, bees
wax, Shellac.

6. ADVANTAGES OF MICROENCAPSULATION
1. Formulation of sustained release and controlled release dosage
forms.
2. Providing environmental protection to the encapsulated active
agents or core materials.
3. Liquids and gases can be converted into solid particles in the form
of microcapsules.
4. Masking of bitter taste of the drugs.
5. Reduce hygroscopic nature of the substance.
6. Reduction of vaporization of volatile drugs.

7. DISADVANTAGES OF MICROENCAPSULATION
1. Expensive techniques.
2. Microencapsulation coating may not be uniform and this can
influence the release of encapsulated materials.
3. Cross reaction between core and shell material is possible.
4. More skill and knowledge is required for formulation of dosage
forms by utilizing microencapsulation techniques.

8. METHODS OF MICROENCAPSULATION
1. Air suspension/Fluidized-bed technique
2. Pan coating
3. Coacervation phase separation
4. Spray drying
5. Solvent Evaporation

9. 1. Air suspension/Fluidized bed technique
• Used for solid core particles, which
are greater than 35 μm in size.
• Solid, particulate core materials are
dispersed in a supporting air stream
through a fluidized bed.
• The coating material is sprayed on
the air suspended particles.
• Within the coating chamber,
particles are suspended on an
upward moving air stream.

10. • The design of the chamber and its operating parameters effect a
recirculating flow of the particles through the coating zone portion of
the chamber, where a coating material, usually a polymer solution, is
spray applied to the moving particles.
• During each pass through the coating zone, the core material receives
an increment of coating material.
• The cyclic process is repeated, perhaps several hundred times during
processing, depending on:
The purpose of microencapsulation.
The coating thickness desired.
Until the core material particles are thoroughly encapsulated.
• The supporting air stream also serves to dry the product while it is
being encapsulated. Drying rates are directly related to the volume
temperature of the supporting air stream.

11. 2. Pan coating
• For relatively large solid core particles,
which are greater than 600 μm in size,
microencapsulation can be done by pan
coating method, which is being widely
used in pharmaceutical industry for the
preparation of controlled release
dosage forms.
• The drug particles are tumbled in a pan,
while the coating material is generally
applied slowly with the moving of the
pan.

12. • 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 as the coatings are
being applied in the coating pans to remove the coating solvent. In
some cases, the process of final solvent removal is accomplished in
the drying oven.

13. 3. Coacervation phase separation
Membrane formation
Involves three steps:
i. Formation of 3 immiscible
phases (a core material phase, a
coating material phase, and a
liquid manufacturing phase)
ii. Deposition of coating
iii. Rigidization of coating.

14. • Used for solid/liquid core particles, which are greater than 2 μm in
size.
• Coacervation phase separation technique involves three major steps:
i. Formation of 3 immiscible phases
ii. Deposition of coating
iii. Rigidization of coating.
i. Formation of 3 immiscible phases (a core material phase, a coating
material phase, and a liquid manufacturing phase):
• Initially the core material is dispersed in a homogenous solution
of coating polymer in which solvent for solubilizing the polymer
is the liquid manufacturing vehicle.
• The coating material is separated from the liquid manufacturing
vehicle to form coacervates by application of any one of the
following principles.

15. • Coacervation is done by:
 Changing the temperature of the polymer solution
 Addition of a salt
 Addition of non-solvent
 Addition of incompatible polymer to polymer solution
 Inducing polymer-polymer interaction.
• Because of the application of the above principles, the solubility of
the polymer in the liquid manufacturing vehicle decreases and the
polymer starts separating in the form of small liquid droplets
called as “Coacervates”. Thus, resulting in formation of three
phases: a liquid manufacturing phase, a core material phase and a
coating material phase

16. ii. Deposition of coating: The deposition of coating material takes
place when the coacervates droplets (polymer) starts arranging
themselves and gets adsorbed over the surface of core material
resulting in formation of a coat around the core particles.
iii. Rigidization of coating: Coating is made rigid by:
Temperature rigidization
Cross-linking
Desolvation (evaporation of solvent)

17. 4. Spray drying
• The pharmaceutical, and biochemical industries
for is technique is widely used in food, chemical,
various applications, including
microencapsulation.
• Basically, it is a continuous one-step and close-
system process where drug is dissolved or
dispersed in concentrated polymer solution and
sprayed into hot gaseous medium of the spray
dryer chamber.
• As a consequence of solvent evaporation, the
polymer rapidly solidifies around drug particles,
which results in formation of either microspheres
or polynuclear microparticles.

18. 5. Solvent Evaporation
Addition of drug polymer
solution to Aqueous
phase
Organic phase
evaporation
Encapsulated particles
Polymer dissolved in
organic solvent
Drug
particles
Drug polymer
solution
&

19. • Used for solid/liquid core particles, which are greater than 5 μm in
size.
• In this method, drug is dissolved or dispersed in the polymer solution
in volatile organic solvent.
• The drug polymer solution is then slowly added to the aqueous phase
with constant stirring.
• Once the emulsion is formed, the organic solvent is removed by
evaporation at elevated temperatures.
• As a consequence of solvent evaporation, polymer shrinks around the
drug forming microcapsules.
• Several techniques can be used to achieve dispersion of the oil phase
in the continuous phase. The most common method is the use of a
propeller style blade attached to a variable speed motor.

20. EVALUATIONS OF MICROPARTICULATE DRUG
DELIVERY SYSTEM
1. Microsphere recovery/yield
2. Drug Entrapment Efficiency
3. Surface Morphology
4. Particle Size Analysis
5. In vitro Release Studies
6. Differential Scanning Calorimetry (DSC) Analysis
7. In vivo Tissue Distribution Studies

21. APPLICATIONS
• Microencapsulation can be used to formulate various sustained and
controlled release dosage forms by modifying or delaying release of
encapsulated active agents or core materials.
• Microencapsulation can also be employed to formulate enteric-
coated dosage forms, so that the drugs will be selectively absorbed in
the intestine rather than the stomach.
• Gastric irritant drugs are being microencapsulated to reduce the
chances of gastric irritation.
• The taste of bitter drugs can be masked by employing
microencapsulation techniques.
• Through microencapsulation, liquids and gases can be changed into
solid particles in the form of microcapsules.

22. • Microencapsulation can employed to aid in the addition of oily
medicines to tableted dosage forms to overcome the problems of
tacky granulations and in direct compression.
• Microencapsulation can be used to decrease the volatility. A
microencapsulated volatile substance can be stored for longer times
without any substantial evaporation.
• Microencapsulation provides environmental protection to the
encapsulated active agents from various environmental issues, such
as light, heat, humidity, oxidation, etc.
• Microencapsulation can reduce the hygroscopic characteristics of
many core materials.

23. • The separations of incompatible substances can be achieved by
microencapsulation. For example, pharmaceutical eutectics can be
separated by microencapsulation. This is a case where direct contact
of materials brings about liquid formation. The stability enhancement
of incompatible aspirin-chlorpheniramine maleate mixture is
accomplished by microencapsulating both of them before mixing.
• Microencapsulation is used to lessen the potential danger of toxic
substance handling. The toxicity owing to handling of herbicides,
insecticides, pesticides and fumigants, etc., can be usefully lessened
after microencapsulation.

24. THANK YOU