Microencapsulation is a process where core materials are surrounded by a continuous film of polymeric material to form microparticles or microcapsules between 3-800μm in size. There are various techniques to microencapsulate such as spray drying, pan coating, and polymerization. Microencapsulation can increase bioavailability, alter drug release, and provide targeted drug delivery. Evaluation of the microcapsules involves measuring yield percentage, particle size, drug content, encapsulation efficiency, and in vitro drug release.

1. MICROENCAPSULATION
shivakumar
B.pharmacy
kottam institute of pharmacy, A.P

2. INTRODUCTION
 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.
 The product obtained by this process is called as micro particles,
microcapsules.
 Particles having diameter between 3 - 800µm are known as micro particles or
microcapsules or microspheres.

3. CLASSIFICATION OF MICROPARTICLE
Generally Micro particles consist of two components
a) Core material
b) Coat or wall or shell material.
1.Microcapsules: The active agent forms a core surrounded by an inert diffusion barrier.
2.Microspheres: The active agent is dispersed or dissolved in an inert polymer.

5. ADVANTAGES:
 To Increase of bioavailability
 To alter the drug release
 To improve the patient’s compliance
 To produce a targeted drug delivery
 To reduce the reactivity of the core in relation to the outside environment
 To decrease evaporation rate of the core material.
 To convert liquid to solid form & To mask the core taste.

6. FUNDAMENTAL CONSIDERATION:
Microencapsulation
Core material Coating material Vehicle
Solid Liquid
Polymers Aqueous Nonaqueous
Waxes
Resins
Proteins
Polysaccharides

7. APPLICATION OF MICROENCAPSULATION TECHNIQUES:

8. Microencapsulation : Applications
Chemistry Medicine & Pharmacy &
Printing & recording vetinary
Carbonless paper,
Adhesives
Control release, Taste masking
Pigments and Vectorisation
Fillers Catalysts Artificial organs
single dose treatment
Food & feed
Aromas, Probiotics Agriculture
Unsaturated oil, Fungicide – herbicide, Insect
Enzyme food processing repellent, Biopesticide
amino acid for cows Pigments and fillers
Artificial insemination
Biotechnology &
environment Consumer & diversified
Continuous reactor, Cosmetics,
Shear protection, detergents (enzymes),
Reactor oxygenation sanitary (active, aromas)

9. MICROENCAPSULATION TECHNIQUES:

10. MICROENCAPSULATION TECHNIQUES:
1. Air suspension techniques( Wurster)
2. Coacervation process
3. Spray drying & congealing
4. Pan coating
5. Solvent evaporation
6. Polymerization
7. Extrusion
8. Single & double emulsion techniques
9. Supercritical fluid anti solvent method (SAS)
10. Nozzle vibration technology

11. Air Suspension Techniques( Wurster)
Microencapsulation by air suspension technique consist
of the dispersing of solid, particulate core materials in a
supporting air stream and the spray coating on the air
suspended particles. Within the coating chamber,
particles are suspended on an upward moving air stream.
The design of the chamber and its operating parameters
effect a recalculating 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.

12. 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 or whether 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.

13. Air suspension techniques
(WURSTER PROCESS):

14. Coacervation process
Formation of three immiscible phases; a liquid manufacturing
phase, a core material phase and a coating material phase.
 Deposition of the liquid polymer coating on the core material.
 Rigidizing the coating usually by thermal, cross linking or
desolvation techniques to form a microcapsule.
In step 2, the deposition of the liquid polymer around the interface
formed between the core material and the liquid vehicle phase. In
many cases physical or chemical changes in the coating polymer
solution can be induced so that phase separation of the polymer
will occur.

15. Droplets of concentrated polymer solution will form and coalesce to
yield a two phase liquid-liquid system. In cases in which the coating
material is an immiscible polymer of insoluble liquid polymer it may
be added directly. Also monomers can be dissolved in the liquid
vehicle phase and subsequently polymerized at interface.
Equipment required for microencapsulation this method is relatively
simple; it consists mainly of jacketed tank with variable speed
agitator.

16. COACERVATION / PHASE SEPARATION
Coacervate
Droplets
SEPARATION
FORMATION
PHASE
MEMBRANE
Droplets
Polymer Solution
1.Formation of three immiscible phase
Membrane
Polymeric
Homogeneous
2.Deposition of coating
3.Rigidization of coating.

17. COMPLEX COACERVATION :

18. Spray-Drying & spray-congealing
Spray-Drying & spray-congealing :
- Microencapsulation by spray-drying is a low-cost commercial
process which is mostly used for the encapsulation of fragrances,
oils and flavors.
Steps:
1- Core particles are dispersed in a polymer solution and sprayed into
a hot chamber.
2- The shell material solidifies onto the core particles as the solvent
evaporates.
- The microcapsules obtained are of polynuclear or matrix type.

19. Spray-congealing
Spray-congealing:
-This technique can be accomplished with spray drying
equipment when the protective coating is applied as a melt.
1- the core material is dispersed in a coating material melt.
2- Coating solidification (and microencapsulation) is
accomplished by spraying the hot mixture into a cool air
stream.
- e.g. microencapsulation of vitamins with digestible
waxes for taste masking.

20. Spray-Drying

21. SPRAY DRYING & CONGEALING ( COOLING)
Spray drying : spray = aqueous solution / Hot air
Spray congealing : spray = hot melt/cold air

22. PAN COATING
1- Solid particles are mixed with a dry coating
material.
2- The temperature is raised so that the coating
material melts and encloses the core particles, and
then is solidified by cooling.
Or, the coating material can be gradually applied to
core particles tumbling in a vessel rather than being
wholly mixed with the core particles from the start of
encapsulation.

24. MULTIORIFIC-CENTRIFUGAL PROCESS
The Southwest Research Institute (SWRI)
has developed a mechanical process for
producing microcapsules that utilizes
centrifugal forces to hurl a core material
particle trough an enveloping
microencapsulation membrane thereby
effecting mechanical microencapsulation.
Processing variables include the rotational
speed of the cylinder, the flow rate of the
core and coating materials, the
concentration and viscosity and surface
tension of the core material. The
multiorifice-centrifugal process is capable
for microencapsulating liquids and solids
of varied size ranges, with diverse coating
materials. The encapsulated product can be
supplied as slurry in the hardening media
or s a dry powder. Production rates of 50
to 75 pounds per our have been achieved
with the process.

25. POLYMERIZATION
A relatively new microencapsulation
method utilizes polymerization techniques
to from protective microcapsule coatings
in situ. The methods involve the reaction
of monomeric units located at the interface
existing between a core material substance
and a continuous phase in which the core
material is dispersed. The continuous or
core material supporting phase is usually a
liquid or gas, and therefore the
polymerization reaction occurs at a liquidliquid,
liquid-gas, solid-liquid, or solid-gas
interface.

26. POLYMERIZATION:
Drug
Monomer(s) (e.g. acrylamide, methacrylic acid) Monodisperse microgels in the micron or
+ Cross-linker (e.g. methylenebisacrylamide)
submicron size range.
Preparation of the
Polymerization Mixture Alcohol
Precipitation polymerization starts from
Addition of the alcoholic solution
a homogeneous monomer solution in
of the initiator (e.g., AIBN) which the synthesized polymer is
insoluble.
Initiation of
Polymerization
The particle size of the resulting
8 hrs Reaction time
microspheres depends on the
polymerization conditions, including the
Monodisoerse Latex
Formation by Polymer monomer/co monomer composition, the
Precipitation
amount of initiator and the total
T (reaction) = 60 °C
monomer concentration.
Nitrogen Atmosphere
RECOVERY OF POLYMERIC
MICROPARTICLES

27. EVALUATION OF MICROCAPSULES
Percentage Yield
The total amount of microcapsules obtained was weighed and
the percentage yield calculated taking into consideration the
weight of the drug and polymer [7].
Percentage yield = Amount of microcapsule obtained /
Theoretical Amount×100
Scanning electron microscopy
Scanning electron photomicrographs of drug loaded ethyl
cellulose microcapsules were taken. A small amount of
microcapsules was spread on gold stub and was placed in the
scanning electron microscopy (SEM) chamber.
The SEM photomicrographs was taken at the
acceleration voltage of 20 KV.

28. Particle size analysis
For size distribution analysis, different sizes in a
batch were separated by sieving by using a set of
standard sieves. The amounts retained on
different sieves were weighed [5].
Encapsulation efficiency [8]
Encapsulation efficiency was calculated using
the formula:
Encapsulation efficiency = Actual Drug Content /
Theoretical Drug Content ×100

29. Estimation of Drug Content
Cefotaxime sodium drug content in the microcapsules was
calculated by UV spectrophotometric (Elico SL159 Mumbai
India) method.
The method was validated for linearity, accuracy and
precision. A sample of microcapsules equivalent to 100 mg
was dissolved in 25 ml ethanol and the volume was
adjusted upto 100 ml using phosphate buffer of pH 7.4. The
solution was filtered through Whatman filter paper. Then the
filtrate was assayed for drug content by measuring the
absorbance at 254 nm after suitable dilution [9].

30. Invitro Drug release Studies
Drug release was studied by using USP type II dissolution test apparatus
(Electrolab TDT 08L) in Phosphate buffer of pH 7.4 (900 ml). The paddle
speed at 100 rpm and bath temperature at 37 ± 0.5°c were maintained
through out the experiment.
A sample of microcapsules equivalent to 100 mg of cefotaxime sodium was
used in each test. Aliquot equal to 5ml of dissolution medium was
withdrawn at specific time interval and replaced with fresh medium to
maintain sink condition. Sample was filtered through Whatman No. 1 filter
paper and after suitable dilution with medium; the absorbance was
determined by UV spectrophotometer (Elico SL159) at 254 nm.
All studies were conducted in triplicate (n=3). The release of drug from
marketed sustained release tablet was also studied to compare with
release from microcapsules.

31. KINETIC ANALYSIS OF DISSOLUTION DATA
To study the mechanism of drug release from the cefotaxime sodium microcapsules,
the release data were fitted to the following equations: (Time in each case was
measured in minutes)
Model 1. Zero order kinetics
Q1==Q0 + Kot
Where,
Q1-amount of drug dissolved in time t
Q0-initial amount of drug in the solution
K0-zero order release constant
Model 2. First order kinetics
Ln Qr = ln Q0K1t
Where,
K1--first order release constant
Q0-initial amount of drug in the solution
Q1-amount of drug dissolved in time t

32. Model 3.Higuchi model
Q= tDCs (2c-Cs)
Where,
Q- Amount of drug release in time t
C- Initial drug concentration
Cs- drug solubility in the matrix
D- Diffusion constant of the drug molecule in that liquid
Model 5.Korsmeyer-Peppas
Mt
M∞ = atn
Where,
a- constant incorporating structural and
geometric characteristics of the drug dosage form
n- the release exponent (indicative of the drug
release mechanism)
Mt/M∞- fractional release of drug.