At the end of the
session, student will be able to:

• Identify mutiparticulate drug delivery systems

• Differentiate between microparticles and macroparticles

• Differentiate between microspheres and microcapsules

• Enlist the methods for microencapsulation

• Describe air suspension technique for microencapsulation

• Discuss the steps in microencapsulation by coacervation
phase separation technique

• Analyze the differences between spray drying and spray
congealing procedures

• Explain microencapsulation by pan coating method

• Discuss solvent evaporation technique for

• Outline interfacial polymerization technique

• Classify coating materials used in microencapsulation with

• Outline the applications of microencapsulation techniques
in pharmaceutical and other fields

to multiparticulate drug delivery system

The active substance is
present in a number of small independent units

To deliver the required dose,
these unites can be filled into sachets, capsules or compressed into tablet

and Macroparticles

Particles having diameter
between 3 – 800µm are known as microparticles or microcapsules or microspheres

Particles   larger  
than   1000µm   are known as Macroparticles



1. Microcapsule           

2. Microsphere


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


• In the encapsulate, the active portion is termed the core,
internal phase, or fill

• The encapsulating material is called the shell, coating,
or wall material and may range in both its thickness and number of layers

• Microcapsules can release their contents at controlled
rates at specific conditions

• Shape – ideally spherical; however, their shape is heavily
influenced by the structure of the unencapsulated material

of Microencapsulation

To Increase of bioavailability

To alter the drug release

To improve the patient’s

To produce a targeted drug

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

To mask the core taste


of Microencapsulation


Printing & recording

Carbonless paper,


Pigments and

Fillers Catalysts

Food & feed

Aromas, Probiotics

Unsaturated oil,

Enzyme food processing amino acid for cows


Fungicide – herbicide,

Insect repellent,


Pigments and fillers

Artificial insemination

Biotechnology & environment

Continuous reactor,

Shear protection,

Reactor oxygenation

Consumer &

Cosmetics, detergents (enzymes), sanitary (active, aromas)

Carbonless copy paper

Mechanisms of Microencapsulation

1. Degradation controlled monolithic system

2. Diffusion controlled monolithic system

3. Diffusion controlled reservoir system

4. Erosion


Air suspension technique

Single & double emulsion

Pan coating


Solvent evaporation

Spray drying and spray Congealing



Air Suspension
Techniques (Wurster)

Wurster Process

Microencapsulation by air suspension technique consist of:

• Dispersing of solid, particulate core materials in a
supporting air stream

• Spray coating the air suspended particles

• Within the coating chamber, particles are suspended on an
upward moving air stream

– The air may be heated or cooled

• 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

– The coating, which may be in a molten state or dissolved
in an evaporable solvent

• 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

– Whether the core material particles are thoroughly

   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.

• The coating is atomised through nozzles into the chamber
and deposits as a thin layer on the surface of suspended particles

• The turbulence of the column of air is sufficient to
maintain suspension of the coated particles, allowing them to tumble and
thereby become uniformly coated.

• Upon reaching the top of the air steam, the particles move
into the outer, downward-moving column of air, which returns them to the
fluidised bed with their coating nearly, dried and hardened

• The particles pass through the coating cycle many times
per minute

• With  each  successive 
pass,  the  random 
orientation  of  the 
particles  further ensures their
uniform coating

• The process typically takes from 2 to 12 hours to complete
and achieves exceptionally good coverage, leaving only about 0.2-1.5% of the
particles uncoated

• Air suspension coating can be used with core particles
ranging from 50 to 500 µm

Various variables to
be considered during this process are:

• Volume of the air required to fluidize and support the

• Coating material application rate and its concentration

• Amount of coating material required

• Temperatures of the inlets and outlets

• Various parameters of core material such as its melting
point, density, surface area, friability, volatility, crystallinity, flow
ability and solubility.



• Bungenberg and colleagues defined as, partial desolvation
of a homogeneous polymer solution into a polymer-rich phase (coacervate) and
the poor polymer phase (coacervation medium)

• The term originated from the Latin ‘coacervate’, meaning “heap”

• This was the first reported process to be adapted for the
industrial production of microcapsules

– Methods

Simple coacervation –
A desolvation agent is added for phase separation

Complex coacervation –
Involves complexation between two oppositely charged polymers.

– Coacervation Technique

STEP 1: Formation
of three immiscible phases

• A liquid manufacturing phase

• A core material phase

• 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

STEP 1: Formation of three immiscible phases

1.   Liquid
manufacturing vehicle

2.   Core material

3.   Coating material

• The core material is dispersed in a solution of the
coating polymer

The three phases are formed by;

Simple coacervation

• Temperature change

• Salt addition

• Nonsolvent addition

• Incompatible polymer addition

Complex coacervation

• Polymer – polymer interaction

1.   Changing temperature of polymer solution

e.g. ethyl cellulose in cyclohexane (N-acetyl P-amino phenol
as core)

2.   Addition of salt

e.g. addition of sodium sulphate solution to gelatine solution
in vitamin encapsulation

3.   Addition of non-solvent

e.g. addition of isopropyl ether to methyl ethyl ketone
solution of cellulose acetate butyrate

4.   Addition of incompatible polymer to the
polymer solution

e.g. addition of polybutadiene to the solution of
ethylcellulose in toluene

5.   Inducing polymer – polymer interaction

e.g. interaction of gum Arabic and gelatin at their
iso-electric point

Step 2: Deposition of liquid polymer upon the core material

• Accomplished by controlled, physical mixing of the coating
material (while liquid) and the core material in the manufacturing vehicle

• Polymer should be adsorbed at the interface formed between
the core and the liquid phase

• Adsorption phenomenon is a pre requisite for effective

Step 3: Rigidization of the coating

Carried out by



   Thermal treatment



Dispersing the core
material in a liquefied coating substance


Spraying or
introducing the core coating mixture into suitable environmental condition


Rapid solidification
of the coating

Rapid solidification
of the coating

Spray drying – Rapid
evaporation of a solvent in which the coating material is dissolved à Coating solution
dissolved in a solvent

Spray Congealing –
Thermally congealing a molten coating material or by solidifying a dissolved coating
by introducing the coating core material mixture into a nonsolvent à Coating applied as a
melt of waxes, fatty acids, polymers and sugars that are solids at room
temperature but melt at reasonable temperature

5 to 600 microns

Spray dryer


Spray drier

Process control

Viscosity, uniformity,
concentration of core and coating material

Feed rate

Method of atomization

Drying rate


Pan Coating

• Microencapsulation of relatively large particles

• Particles larger than 600 microns

• Controlled release beads

• Coating solution atomized on the particles in the coating

• Solvent removed by passing warm air over the coated

• Or by drying in an oven


Solvent evaporation

Drug Dissolved or dispersed in Solution of polymer in a
volatile solvent à
Dispersed àLiquid
manufacturing vehicle à
Removal of solvent

Process variables → solvent for the polymer, temperature
cycle, agitation rates



• Reaction of monomeric units located at the interface
existing between a core material and
continuous phase                                                                                                                   


Water soluble resin

 • Gelatin

• Gum Arabic



• Methyl cellulose

• Arabinogalactan

• Polyvinyl acrylate

• Polyacrylic acid

Water insoluble resin

 • Ethyl cellulose

• Polyethylene

• Polymethacrylate

• Cellulose nitrate

• Silicones

Wax & lipid

 • Paraffin

• Carnauba wax

• Bees wax

• Stearic acid

• Stearyl alcohol

Enteric resin



Cellulose acetate phthalate



• 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, Methyl salicylate

• To avoid incompatibilities. e.g. Aspirin and

• To mask the unpleasant taste and odour. e.g.
Aminophylline, castor oil

• To convert liquids into solids. e.g. Castor oil,

• To reduce gastric irritation. e.g. Nitrofurantoin,

Microencapsulation in
paint industry

• Products such as acrylics, powder coatings, urethane
paints, are key product types currently used with microencapsulation

Thermo-chromic &
photo-chromic apparels/fabrics

• These  fabrics  change 
colour  as  an 
effect  of  change 
in  temperature  in  the

• Within the fabric, the microencapsulated colourings are
responsive to thermal changes and light sensitive changes.

Carbonless Paper

• With carbonless paper, the copy is produced by a chemical
reaction between two different coatings (Color producing substance and reacting
substance), which are generally applied to the front and back of a base paper

• This color reaction is caused by pressure (typewriter,
dot-matrix printer, or writing instrument).


• Microcapsules containing fragrances (essential oils) are
applied to paper

• They stay enclosed in the (micro) capsule until pressure
force is applied, under which microcapsule shell ruptures and releases the core

• These microcapsules are mostly used in
“scratch-n-sniff” applications e.g. samples perfume inserts in the
newspapers and magazines, promotional advertising campaigns, etc.

Food industry

• Microencapsulated flavors, lipids, and pigments

• Microencapsulation of coffee flavors improves the
protection from light, heat and oxidation when in the dry state, but the core
is released upon contact with water

• Microencapsulated L. acidophilus in cheese

• Microencapsulated probiotics by emulsification in
alginate-chitosan, demonstrating more resistance in simulated gastrointestinal

• Encapsulated aspartame – improving the protection even at


• Controlled Release of Crop Protection Products – a
pesticide product may be most effective at certain humidity or pH levels, or
need to be targeted to the leaves or the roots of the plant

• Sophisticated encapsulation technologies can be designed
with appropriate triggers for maximum efficacy. A pesticide that works on the
leaves of the plant, for example, may be triggered by UV exposure. Another
agrichemical that needs to be applied to the roots in wet conditions may only
be released when rain washes it down into the soil


Encapsys, LLC

• Provides microencapsulation solutions for paints and
coatings, agriculture, oil and gas, adhesives and sealants, personal and household
care, and paper industries.

Reed Pacific Pty

microencapsulation technology for many different applications such as

– Insect repellent

– Healthcare

– Agriculture

– Consumer products (fabric care and personal care)

– Cosmetic & skin care

– Industrial actives

– Defense & aviation

Ronald T. Dodge

• The company offers services such as microencapsulation,
fragrance delivery, controlled release, encapsulated products, coacervation,
scented coatings, and inks

GAT Microencapsulation

• Generic agrochemical products (agro-generics) and biocidal
products such as herbicides, insecticides, acaricides, fungicides, and biocides


• The company offers microencapsulation for human and animal
nutrition, biotechnologies, and chemical industries by using dripping
technology, emulsion- based technology, and coating technology

Laboratories, Inc.

• Microencapsulated materials are utilized in agriculture,
pharmaceuticals, foods, cosmetics and fragrances, textiles, paper, paints,
coatings and adhesives, printing applications, and many other industries

Aveka, Inc.

• It offers custom particle processing, manufacturing,
powder process research and development, consulting, prilling, spheroidization,
dry powder coating, and encapsulation services.

TasteTech Ltd.

• The company offers core-shell encapsulation, matrix
encapsulation, spray drying, power stabilization, flavor development, and
contract manufacturing services. The company serves bakery, chewing gum, confectionery,
and sports nutrition markets.

LycoRed Ltd.

• Develops and supplies premixes and microencapsulated
carotenoids, vitamins, minerals, and specialty ingredients for dietary
supplementation, food fortification, coloring, and flavor enhancement applications

Innobio Limited

• The company provides specialty fatty acids, carotenoids,
and branched- chain amino acids

• It offers its product to health concerning markets such as
sport nutrition, weight management, eye health, cognition, vascular care, and


• Microparticles are a kind of multiparticulate dosage forms

• Microparticles can be in the form of microspheres or

• Microencapsulation if the process of applying polymer
coatings to tiny droplets or particles of liquid or solid material

• Microencasulation has several advantages in biomedical,
pharmaceutical and other fields

• Microencapsulation by air suspension (Wurster) coating
involves application of polymer coat to particles suspended in a stream of air

• Coacervation – Simple and complex

• Steps – Formation of three phases, deposition of coat,
rigidization of coat

• Pan coating – for larger particles

• Solvent evaporation – for organic solvent for polymer

• Spray drying and congealing – by atomizing polymer, core,
solvent mixture in a suitable polymer

• Interfacial polymerization – Reaction of monomeric units
located at the interface existing between a core material and continuous phase

can be applied to all sectors of industrial activity

1. Food & Feed

• Flavouring agents & sweeteners

• Enzymes & micro-organisms

• Vitamins, minerals & amino acids

• Plant extracts, aromas, fragrances

• Unsaturated fatty acids            

2. Agriculture &

• Insecticides and fungicides

• Herbicides and fertilizers

• Repellents and larvicides

• Plant biocontrol & bionutrition

• Water, soil, air treatment

3. Human & Animal

• Vaccination & drug delivery

• Artificial insemination

• Bioartificial organs

• Cell therapy

4. Chemistry

• Adhesives and sealants

• Paints and coatings

• Building & construction materials

• Self-healing materials & PCM

5. Home &
Personal Care

• Cosmetic creams

• Shampoo, toothpaste, soap & shower gels

• Washing powders & washing-up liquids

• Household products

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