Microencapsulation is a process in which tiny particles or droplets are surrounded by a coating to give small capsules, of many useful properties. In general, it is used to incorporate food ingredients, enzymes, cells or other materials on a micro metric scale.

1. By Ms. Gauri. R. Kaphare
(Department of Pharmaceutics)
Microencapsulation

2. Microencapsulation is a means of applying thin uniform coatings to
micro particles of solids dispersion or droplets of liquids.
• Microcapsules are small particles that contain an active agent (core material)
surrounded by a shell or coating.
• Their diameters generally range from a few microns to a few millimeters.
• Microcapsules can have many different types and structures:
A. Simple droplets of liquid core material surrounded by a spherical shell
(Microcapsules)
B. Irregularly-shaped particles containing small particles of solid core
material dispersed in a continuous polymer shell matrix (microspheres).
Microencapsulation
• Introduction

3. Types Of Microencapsulation :

4. Fundamentals : • .
Microencapsulation
Core
Material
Solid Liquid
Coating
Material
Polymer
Resins
Polysaccharide
Proteins
Waxes
Vehicle
Aqueous Non Aqueous

5.  The core material is the material to be coated, which may be liquid or solid in
nature.
 The composition of the core material can be varied:
 The liquid core can include dispersed and/or dissolved material.
 The solid core can be a mixture of active constituents, stabilizers, diluents,
excipients , and release-rate retardants or accelerators.

6.  Be capable of forming a film that is cohesive with the core material
 Be chemically compatible and non-reactive with the core material
 Provide the desired coating properties, such as strength, flexibility,
impermeability, optical properties, and stability.
 Coating material selected from natural and synthetic film-forming polymers
like:
- carboxy methyl cellulose - ethyl cellulose
- cellulose acetate phthalate - poly vinyl alcohol
- gelatin, gelatin- gum arabic - poly hydroxy cellulose
- waxes - chitosan

7. Microencapsulation Method :

9. Coacervation-Phase Separation :
 Coacervation is Colloidal phenomenon.
 It is coacervate is tiny spherical droplet.
 Coacervate means aggregation.
Coacervation Phase
Simple Coaservation
Uses one or two which
is pipette out by salt or
non solvent or by
increase or decrease in
temperature
Complex Coaservaion
Uses of two or more
colloidal and salting out is
carried out by oppositely
charged polymer . Eg.
Acalatia & Gelatin

11. Step 1 : Formation of three phases

12. Step 2 : Coating of Polymer Around Core
 As soon as Polymer gets coaservated from solution it forms coating around
core material and then it is rigidized with Physical OR Chemical means.
 The coaservation deposits around core particle by :
a) Coalescence of many inviduals droplets around core.
b) Single coaservate droplet may encompass ore or more particles.

13. Step 3 : Rigidization of Coat
 Essential to impart stability and protection from drug leaching from
microcapsule.
Methods
Cross
linking
polymer
Thermal
process
Desolvation
Aqueous
Vehicle
Non-Aq.
Vehicle
Salting
Agent

14. Polymer-polymer incompatibility :
 This method utilizes two polymers that are soluble in a common solvent, yet
do not mix with one another in the solution
 Polymer form two separate phases, one rich in polymer intended to form the
capsules walls, the other rich in the incompability polymer meant to induce
separation of the incompatible polymer meant to induce separation of the
two phases.
 The second polymer is not intended to be part of the finished microcapsules
wall.

16. Interfacial Polymerization :
 The process is based on formation by interfacial polymerization reaction of
two monomer dissolve in an aqueous or organic phase.
 Two monomers in a polycondensation or polyaddition meet at interface and
condensed polymer wall form instantaneously at the interface of the emulsion
droplets.
 The degree of polymerization can be controlled by :
a) Temperation
b) Monomer concentration
c) Composition of either phase
 Example of wall material : Polyamide, polyuria, polyurethane epoxy resin.

19. In-Situ Polymerization :
 In this process direct polymerization of single monomer unit is carried out on
particle surface.
 E.g. : Cellulose fiber are encapsulated in polyethylene while immersed in dry
toluene.
 Usual deposition rate are about 0.5 micro meter / min.
 Coating thickness ranges 0.2 to 0.75 micro meter
 Matrix is uniform even over sharp projections.

21. Air Suspension :
Microencapsulation by air suspension techniques using Wurster
Air Suspension Apparatus
A. control panel
B. coating chamber
C. particles being treated
D. process airflow
E. air distribution plate
F. nozzle for applying film coatings

22. Principle :
 The Wurster process consists of the dispersing of solid particulate core materials in
a supporting air stream and the spray-coating of the air suspended particles.
 Within the coating chamber, particles are suspended on an upward moving air
stream as indicated in the drawing.
 The design of the chamber and its operating parameters provide 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 several times during processing, depending on the
purpose of microencapsulation, the coating thickness desired.
 The air stream also serves to dry the product while it is being encapsulated.

23. Capability of air suspension :
 The process has the capability of applying coatings in the form of solvent
solutions, aqueous solutions, emulsions, dispersions, or hot melts
 The coating material selection appears to be limited only in that the coating
must form a cohesive bond with the core material.
 The process generally is applicable only to the encapsulation of solid core
materials
 Particle size, The air suspension technique is applicable to both
microencapsulation and macroencapsulation coating processes with particle
size range 35-5000 µm

24. Fluidized bed coater solvent extraction :
 Fluidized bed coater has become more popular.
 They are used for encapsulating solid or porous particle with optimum heat
exchange.
 The coating is spread on particle and the rapid evaporation helps in formation
of an outer layer on the particles.

25. Types of fluid bed
coaters
3.
Tangential
spray
2. Top
Spray
1. Bottom
spray

26.  Top Spray : In this the Coating Material is sprayed downwards on the fkuid
such that as the solid or porous particle move to the coating region become
encapsulated. Increased encapsulation efficiency and prevention oil cluster
formation.
 Bottom spray : This is also known as “ Wurster’s coater “. This technique uses
coating chamber that having cylindrical nozzles and perforated bottom plate.
The cylindrical nozzle is used for spraying coating material. As particle move
upward through the perforated bottom plate and pass though nozzle area, they
are encapsulated by coating material.
 Tangential Spray : It consist of rotating disc at the bottom of the coating
chamber with same diameter as the chamber. During process the disc is raised
to create gap between edge of chamber and disc. The tangential nozzle is
placed above the rotating disc through which the coating material is released.
The particle move through the gap into the spraying zone and are
encapsulated.

28. Rotational Suspension Separation :

29. Extrusion and Spheronization :
 Dispersion of core material in molten carbohydrate mass.
 Extruded in dehydrating liquid for hardening.
 Spheronization.
 Separation & dyeing.

31. Spray Drying and Spray Congealing :
The Spray dryer equipment components include :
1 •Air heater
2 •Atomizer spray chamber
3 •Cyclone
4 •Product Collector
5 •Fan

32. Spray Drying and Spray Congealing :
 Microencapsulation is conducted by dispersing a core material in a coating
solution, in which the coating substance is dissolved and in which the core
material is insoluble, and then by atomizing the mixture into a heated air stream.
 Microencapsulation by spray-congealing can be accomplished with spray drying
equipment when the coating is applied as a melt .
 General process variables and conditions are quite similar to those spray drying ,
except that the core material is dispersed in a coating material melt rather than a
coating solution.
 Waxes, fatty acids polymers , alcohols, and sugars, which are solids at room
temperature but meltable at reasonable temperatures, are applicable to spray-
congealing techniques.
 Coating solidification (microencapsulation) is accomplished by spraying the hot
mixture into a cool air stream

33. Solvent evaporation :
This methodof microencapsulation is the most
widely used due to :
Simple technique.
This method allow encapsulation of hydrophobic and hydrophilic drug
This method allow encapsulation of solid and liquid drug
Microcapsule produced have wide size rang (5-5000µm)

34. Solvent Evaporation Diagram :

35. Pan Coating :
 Pan Coating process is used for 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 as the coatings are being
applied in the coating pans to remove the coating solvent.
 Final solvent removal is accomplished in a drying oven.
 The coating operation is repeated three times. Then coating followed by
dusting with talc the microcapsules are rolled until drying, and the excess
talc is removed by vacuum.
 The product is then screened through a 12mesh screen

36. Pan Coating Diagram :

38. Evaluation of Micro capsule :
•Particle size varies from 0.001-2000 micron. Method used
are Optical microscopy, Sieve analysis etc.
1.Particle size and distribution :
•Shape is determined by Phase contrast microscopy &
Surface morphology is determined by scanning electron
microscopy.
2. Shape and Surface
Morphology :
•Dilute Solution viscometry & Gel permeation viscometry
are methods used for Mol. Wt. distribution.
3. Molecular weight and
molecular weight distribution :
•Mercury intrusion is used for pore size and density of
microcapsule. Helium compression pycnometry is another
method used to determine pore density.
4. Porosimetry :
•Differential scanning calorimetry is used for
determination of drug performance after encapsulation in
term of change in drug behavior.
5. Thermal Analysis :
•Zetasizer and tensiometry are used for determining
Surface property and hydrophobicity.
6. Surface property :
•X-ray diffraction used to determine crystallinity.7. Crystallainity :

39. Merits of microencapsulation :
Merits
Food
production
have
increased
health
benefits.
Do not
interfere
with other
ingredients
Can be
added
anytime in
processing
& remains
unaltered
Shelf life
may be
Increased
Sensory
properties
remain
unaltered
Consumer
would not
get taste of
added
capsules
Wider range
of products
for
consumer to
choose from

40. Demerits of Microencapsulation :
Demerits
Due to
Foreign
ingredient
customer
with allergies
may face
problems
More skill and
knowledge is
required to use
this technology
Production
Cost is High
Shelf life of
hygroscopic
drug is
reduced
Difficult to
achieve
continuous
and uniform
film
Possible cross
reaction may
occur in wall
and material
selected

41. Application of Microencapsulation :

48. Conclusion :