LinkedIn emplea cookies para mejorar la funcionalidad y el rendimiento de nuestro sitio web, así como para ofrecer publicidad relevante. Si continúas navegando por ese sitio web, aceptas el uso de cookies. Consulta nuestras Condiciones de uso y nuestra Política de privacidad para más información.
LinkedIn emplea cookies para mejorar la funcionalidad y el rendimiento de nuestro sitio web, así como para ofrecer publicidad relevante. Si continúas navegando por ese sitio web, aceptas el uso de cookies. Consulta nuestra Política de privacidad y nuestras Condiciones de uso para más información.
Saran Kumar Das
Department Of Pharmaceutics
Al-Ameen College Of Pharmacy
Definition of Micro encapsulation
Reasons for Micro encapsulation
Core and Coating Materials
Mechanism of Drug Release
Core and Coating Materials
Microencapsulation may be defined as the process of surrounding
or enveloping one substance within another substance on a very
small scale, yielding capsules ranging from less than one micron
to several hundred microns in size.
Microencapsulation is the process by which tiny solid particles or
droplets of liquid are surrounded or coated with a continuous film
of polymeric material to produce capsules in the micrometer to
millimetre range. The product obtained by this process is called as
It is mean of applying thin coating to small particle of solid or
droplet of liquid & dispersion.
Particle size: 50-5000 micron.
It has 2 main phases: a) Core material b) Coating material
Also known as microcapsule, microsphere, coated granules,
For sustained or prolonged drug release.
For masking taste and odour of many drugs to improve patient
For converting liquid drugs in a free flowing powder.
To reduce toxicity and GI irritation
Incompatibility among the drugs can be prevented by
The drugs, which are sensitive to oxygen, moisture or light, can
be stabilized by microencapsulation 6
The material to be coated :-
It may be liquid or solid
Liquid core may be dissolved or dispersed material
Composition of coating material:
Drug or active constituent
Additive like diluents
Release rate enhancers
Inert substance which coats on core with desired thickness
Compatible with the core material
Stabilization of core material.
Inert toward active ingredients.
Controlled release under specific conditions.
The coating can be flexible, brittle, hard, thin etc.
Abundantly and cheaply available
Composition of coating :-
Colouring agent 8
Mechanism of Drug Release
1)Degradation controlled monolithic system- Drug releases on
degradation of matrix.
2)Diffusion controlled monolithic system- Drug released by
diffusion then degradation of matrix occurs.
3)Diffusion controlled reservoir system- Drug from capsule
diffuses then rate controlling membrane erodes.
4)Erosion-Due to pH and enzymatic hydrolysis.
To improve the flow properties. e.g. Thiamine, Riboflavine
To enhance the stability. e.g. Vitamins
To reduce the volatility of materials. e.g. Peppermint oil,
To avoid incompatibilities. e.g. Aspirin and Chloramphenicol
To mask the unpleasant taste and odour. e.g. Aminophylline,
To convert liquids into solids. e.g. Castor oil, Eprazinone,
To reduce gastric irritation. e.g. Nitrofurantoin, Indomethacin
Possible cross reaction between core and shell material.
Difficult to achieve continuous and uniform film.
Shelf life of hygroscopic drugs is reduced.
More production costs.
More skill and knowledge is required
Microcapsule is a tiny capsule , containing material such as
medicine, that is released when the capsule is broken , melted
Microcapsules contain an active agent and surrounded
polymeric shell or dispersed in polymeric matrix.
Microcapsule size : 1 to 1000 micron
Microcapsules can be of different structures
Category of Coating
Water soluble resins Gelatin,
Water insoluble resins Ethyl cellulose, Polyethylene
Waxes and lipids Paraffin, Carnauba, Beeswax
Enteric resins Shellac, Zein
Physical Methods Chemical
A) Air Suspension Solvent Evaporation
B) Pan Coating Polymerization
C) Coarcervation Phase Separation
D) Multi-orifice Centrifugal Process
E) Spray Drying & Spray Congealing
F) Fluidized Bed Technology
1 Air Suspension Solid 35-5000 Pilot Scale High High
2 Pan Coating Solid 600-
Pilot Scale High High
2-5000 Lab Scale Less Less
1-5000 Pilot Scale High High
5-5000 Lab Scale Less Less
6 Spray Drying
liquid 600 Pilot Scale High High
Within the coating chamber, particles are suspended on an upward
moving air stream.
Spraying of coating material on the air suspended particles.
The cyclic process is repeated depending upon purpose of
Air stream serves to dry the product.
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
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.
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
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. 29
Concentration of Coating materials
Solubility , Surface area, density, melting point and Volatility.
Application rate of coating materials
Temperature of air stream.
The amount of required to fluidized the core materials.
The particles are tumbled in a pan while the coating
material is applied slowly as solution or atomized spray to
To remove the coating solvent, warm air is passed over the
Medicaments are usually coated onto nonpareil sugar
seeds and then coated with polymers
Solid particles are mixed with a dry coating material.
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.
Suitable to larger
High material loss
Simple coacervation Complex coacervation
A desolvation agent is added for
It involves complexation
between two oppositely
Steps involved in this process are:-
1)Formation of three immiscible phases.
2)Deposition of liquid coating material upon the core material.
3) Rigidization of coating.
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.
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.
Various methods to obtain three immiscible phases
1) Temperature change
2) Incompatible Polymer Addition
3) Non-Solvent Addition
4) Salt Addition
5) Polymer-Polymer Interaction(Complex Coacervation)
Temperature Change:- Changing temperature of polymer
solution, Example:- Ethyl cellulose in cyclohexane.
Incompatible polymer addition :- Addition of incompatible
polymer to the polymer solution , e.g. Addition of
polybutadiene to the solution of ethyl cellulose in toluene.
Non Solvent Addition:- e.g. Addition of isopropyl ether to
methyl ethyl ketone solution of cellulose acetate butyrate.
Addition of Salt :- e.g. Addition of Sodium sulphate solution
to gelatin solution in vitamin encapsulation
Polymer-polymer interaction:- e.g. Interaction of gum arabic
and gelatin at their isoelectric point
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 as a dry powder.
Production rates of 50 to 75 pounds per our have been achieved
with the process.
Cylinder Rotating Speed
Core and Coating materials Flow Rate
Concentration of Core material
Encapsulates both solid and liquid materials.
Production rate is more.
Spray Drying : Microencapsulation by spray-drying is a low-
cost commercial process which is mostly used for the
encapsulation of fragrances, oils and flavours.
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.
The coating solidification effected by rapid evaporating of
solvent in which coating material is dissolved.
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
The coating solidification is effected by thermally congealing a
molten coating material. The removal of solvent is done by
sorption, extraction or evaporation technique
The liquid coating is sprayed onto the particles and the rapid
evaporation helps in the formation of an outer layer on the
The thickness and formulations of the coating can be obtained as
desired. Different types of fluid-bed coaters include top spray
,bottom spray, and tangential spray
In the top spray system the coating materials is sprayed
downwards onto the fluid bed such that as the solid or porous
particle move to coating region they become encapsulated.
The bottom spray is also known as “Wurster`s Coater” in
reorganization of its development by Prof. D.E. Wurster.
The tangential spray consists of a rotating disc at the bottom
of the coating chamber , with the same diameter as the
chamber. During the process the disc is raised to create a gap
between edge of the chamber and the disc. The tangential
nozzle is placed above the rotating disc through which coating
material is released . The particle move through the gap into the
spraying zone and are encapsulated. As they travel a minimum
distance there is higher yield of encapsulated particles.
Dissolved Or Dispersed
Coating polymer solution
Liquid Manufacturing Vehicle Phase
Heating (If necessary)
Evaporation of Polymer solvent
This technique has been used by companies including the NCR
Company, Gavert Photo production NV, and Fuji Photo Film Co.
Ltd. To produce microcapsule.
In this, Volatile Solvent is Dissolved in microcapsule coating
material, which is immiscible with the liquid manufacturing
The core material to be encapsulated is dispersed in the solution
of coating polymer .Continuous agitation is carried out, and then
core coating material mixture is dispersed in the liquid
manufacturing vehicle phase to give specific size of microcapsule.
Then the solvent evaporate from the polymer solution after
heating the mixture.
The solvent evaporation technique is used to formulate various
types of microcapsule, for example, evolution of sucrose esters as
an alternative surfactants in microencapsulation of proteins by the
solvent evaporation method.
The method involve the reaction of monomeric unit located at
the interface existing between a core material substance and
continuous phase in which the core material is disperse.
The core material supporting phase is usually a liquid or gas,
and therefore polymerization reaction occur at liquid-liquid,
liquid-gas, solid-liquid, or solid-gas interface.
E.g. In the formation of polyamide (Nylon) polymeric reaction
occurring at liquid-liquid interface existing between aliphatic
diamine & dicarboxylic acid halide.
Preparation of the polymerization
Drug Monomer(s) (e.g. acrylamide)
Initiation of Polymerization
Monodisoerse Latex Formation by
Recovery of Polymeric
Addition of the alcoholic
solution of the initiator
8 hrs reaction
A solid jet of fluid coming out of a nozzle by means of rotating
cutting wires is cut into cylindrical segments which then form
beads due to surface tension on their way to a hardening
1)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.
Percentage yield = Amount of microcapsule obtained / Theoretical
2)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. 78
3)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
4)Encapsulation efficiency:- Encapsulation efficiency was
calculated using the formula.
Encapsulation efficiency = Actual Drug Content /
Theoretical Drug Content ×100
5) Estimation of Drug Content:- Drug content in the microcapsules
was calculated by UV spectrophotometric 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 up to 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 specific wavelength after suitable dilution.
6) Invitro Drug release Studies
Drug release was studied by using USP type II dissolution test
apparatus 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 drug 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 at specific wavelength.
All studies were conducted in triplicate (n=3). The release of drug
from marketed sustained release preparation was also studied to
compare with release from microcapsules.
7) Diffusion:- Diffusion is a common mechanism of drug release
in which dissolution fluid penetrates the shell and then core
material comes in contact with the fluid and leak out through the
interstitial channels or pores.
The kinetic of this release is given by Higuchi`s equation:-
Q= t DCs (2c-Cs)
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
8) Thermal Analysis:- It is use for determination of drug
performance after encapsulation in terms of change of drug
behaviour and studied by DSC.
9) Molecular Weight:- Molecular Weight of the microcapsule is
done by Gel Permeation Chromatography.
SL No. Brand Name Generic Name Category of
1 Lupin Cafedroxil Antibiotic
2 Zorprine CR Aspirin Anti - arthritic
3 Glipizide SR Glucotrol Anti diabetic
Micro encapsulation ppt by – SANA TABASSUM
A Review on Microcapsules :- Azagheswari, Binil Kuriokase,
Sathireddy Padma and S. Padma Priya
Micro-encapsulation : at Crossroads of Art, Science and
MICROENCAPSULATION: A REVIEW JYOTHI SRI.S* ,
A.SEETHADEVI , K.SURIA PRABHA ,
P.MUTHUPRASANNA AND ,P.PAVITRA