sarada mec 2.pptx

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By

SARADA ANEPU



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.

Particles having diameter between 3 - 800µm are known as micro particles or

microcapsules or microspheres.

Particles larger than 1000µm are known as Macroparticles .



To mask the bitter taste of drugs

To reduce gastric irritations

A liquid can be converted to a pseudo-solid for easy handling and storage

Hygroscopic properties of core materials may be reduced bymicroencapsulation

To reduce their odor and volatility.

Protection to the core materials against atmospheric effects

Separation of incompatible substance



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.

Microcapsules have well defined core and well defined envelope

2.Microspheres: The active agent is dispersed or dissolved in an inert polymer



RELEASE MECHANISMSDisruption of the coating by pressure, shear or abrasive force

Permeability change brought about by enzymatic fluid

The wall melts away from the core releasing the core in an environment such as

that occurring during baking

The core diffuses through the wall at a slow rate due to the influence of an

exterior fluid such as water or by an elevated temperature

Rate of release depends on

Permeability of coating material to extraction fluid

Dissolution rate of core

Coating thickness

Concentration across the membranes



o The material to be coatedo It may be liquid or solid or gas.

o Liquid core may be dissolved or dispersed

materialCOMPOSITION OF CORE MATERIAL:

o Drug or active constituent

o Additive like diluentso Stabilizers

o Release rate enhancers or retardants



Inert substance which coats on core with desired

thickness

IDEAL CHARACTERISTICS:o Capable of forming a film cohesive with core

materialo Chemically compatible with the core materialo Should be stable, non reactive & cheapo Provide desired coating properties like strength,

flexibility& impermeability

COMPOSITION OF COATINGo Inert polymer o Plasticizer o Coloring agent



Non biodegradable

Acrolein

Epoxy polymers

Biodegradable

Polyesters

Poly ortho esters

Poly anhydrides

Polyphosphazenes

SyntheticProteins

Albumin

Gelatin

collagen

Carbohydrates

Starch

AgaroseCarragreen

Chitosan

Natural



Physical

• Pan Coating• Fluidized bed

• Multi orifice-centrifugalprocess

• Spinning disc• Spray drying

Physicochemical

• Coacervation• Single

emulsion

• Doubleemulsion

• RESS method• SAS method

Chemical

• SolventEvaporation

• Interfacialpolymerisation

• Matrix

Polymerisation



Pan Coating

Air suspension

Centrifugalextrusion

Spinning disc

Spray drying



Two steps;

Preparation of core Coating procedure



Air suspension process:



Multiorifice-centrifugal process, developed by the SouthwestResearch Institute as a mechanical process for producingmicro-capsules that utilizes centrifugal forces to hurl a corematerial particle trough an enveloping microencapsulationmembrane thereby affecting mechanical microencapsulation.

The factors that affect process include the rotational speed of the cylinder, the flow rate of the coating and core materials andthe concentration, viscosity and surface tension of the corematerial.

This process is capable of producing the microencapsulation of the liquids and solids of varied size ranges, by applying thedifferent coating materials.

The encapsulated product can be supplied as slurry in thehardening media



In rotational suspension separation, or thespinning disk method internal phase is dispersedinto the liquid wall material and the mixture isadvanced onto a turning disk.

Droplets of pure shell material are thrown off of the rim of the disk along with discrete particles of core material enclosed in a skin of shell material.

After having been solidified by cooling, themicrocapsules are collected separately from theparticles of shell material



An emulsion is prepared by dispersing thecore material, immiscible with water, intoa concentrated solution of wall materialuntil the desired size of oil droplets areattained.

The resultant emulsion is atomized into aspray of droplets by pumping the slurrythrough a rotating disc into the heatedcompartment of a spray drier.

There the water portion of the emulsion isevaporated, yielding dried capsules of variable shape containing scattered drops

of core material. The capsules are collected through

continuous discharge from the spraydrying chamber



Coacervation

Single emulsionDouble emulsion

RESS method

SAS method



Polymeric

Membrane

DropletsHomogeneous

Polymer SolutionCoacervate

Droplets

PHASE

SEPARATION

MEMBRANE

FORMATION

1.Formation of three immiscible phases

2.Deposition of coating

3.Rigidization of coating.



Deposition of coating

This step consits of depositing liqudpolymer on core

Deposition ocuurs onthe interface which ispromoted by decrease

in interfacial energy

Rigidization of coating

Rigidisation of coatingoccurs by

thermal cross linking or desolvation technique



Natural polymers are

dissolved in aqueous

medium followed by

dispersion in aqueousnon aqueous medium

For dispersion cross

linking is carried out byheat or chemical

agents



Involves preperation of

multiple emulsions,

water soluble drugs

Primary emulsionprepared subjected to

homogenisation

Aq. Solution of polyvinyl alcohol added

At reduced pressure

solvent is removed



Pressurized supercritical

solvent containing the shellmaterial and the active

ingredient is released througha small nozzle

The abrupt pressure drop

causes the desolvation of the

shell material and theformation of a coating layer

around the active ingredient.



This process is also called supercriticalfluid anti-solvent (SAS) method. Wheresupercritical fluid is added to a solutionof shell material and the activeingredients and maintained at highpressure.

This leads to a volume expansion of thesolution that causes super saturationsuch that precipitation of the soluteoccurs.

Thus, the solute must be soluble in the

liquid solvent, but should not dissolve inthe mixture of solvent and supercriticalfluid.

On the other hand, the liquid solventmust be miscible with the supercriticalfluid.



Solvent Evaporation

Interfacial polymerization

Matrix Polymerization



Polymer

+ Volatile organic solvent

Organic Polymeric Phase

Formation of Oil-in-Water

Emulsion

Solvent Evaporation

Particle Formation by

Polymer Precipitation

RECOVERY OF POLYMERIC

MICROPARTICLES

Temperature increase

Active

Ingredient

Addition into an aqueous

phase (+o/w stabilizer)

SOLVENT EVAPORATIONS

Step 1:

Formation of a solution/dispersion of

the drug into an organic polymer

phase.

Step 2:

Emulsification of the

polymer phase into an aqueous phase

containing a suitable stabilizer, thus,forming a o/w emulsion.

Step 3:

Removal of the organic

solvent from the dispersed phase by

extraction or evaporation leading to

polymer precipitation and formationof the microspheres.



Reaction of monomeric

units

Drug is dispersed in thepolymeristion mixture

Alcoholic solution isused as initiator

Polymers precipitate

Microparticles

recovered

Drug

Addition of the alcoholic solution

of the initiator (e.g., AIBN)

8 hrs Reaction time

Monomer(s) (e.g. acrylamide, methacrylic acid)

+ Cross-linker (e.g. methylenebisacrylamide)

Alcohol

T (reaction) = 60 °C

Nitrogen Atmosphere

Preparation of the

Polymerization Mixture

Initiation of

Polymerization

Monodisperse Latex

Formation by Polymer

Precipitation

RECOVERY OF POLYMERIC

MICROPARTICLES



Proceeds with reaction of monomers at theinterface between two immisible liqud phases toform a film of polymer which envelops dispersedphase

One monomer is dissolved and other is dispersedContinuous phase is usually aqueous in which 2nd

monomer is emulsified

Monomers at either phase diffuse rapidly andpolymerise at interface of core particles



In a number of processes, a core material isimbedded in a polymeric matrix duringformation of the particles.

A simple method of this type is spray-drying, inwhich the particle is formed by evaporation of the solvent from the matrix material.

The solidification of the matrix also can becaused by a chemical change.



Process Coating material Suspended medium

Interfacial polymerisation Water-soluble andinsoluble monomers

Aqueous/organic solvent

Complex coacervation Water-solublepolyelectrolyte

Water

Coacervation Hydrophobic polymers Organic solvent

Solvent evaporation Hydrophilic orhydrophobic polymers

Organic or water

Spray drying Hydrophilic orhydrophobic polymers

Air, nitrogen



Stability testing

Size of microcapsules- Sieving Method

Amount of drug present In microcapsules

Viscosity of polymer solutions

Dissolution test- In vitro drug release



Separation of the microspheres into various sizefractions can be determined by using amechanical sieve shaker

The sieves (20, 30, 45, 60 and 80 mesh) arearranged in the order of decreasing aperturesizere shaken for a period of about 10 min, and

then the particles on the screen are weighed



The surface morphologies of microspheresare examined by a scanning electronmicroscope

Nature of the microspere is examinedThe microspheres are mounted onto a copper

Cylinder by using a double-sided adhesive

tape.



Bulk density tapped density are determined

The Hausner ratio of the microcapsules is

determined by the following relationshiphr = ρ tapped/ρ bulk

Where ρ tapped is tapped density

ρ bulk is bulk density.



The absolute viscosity, kinematic viscosity,and the intrinsic viscosity of the polymersolutions in different solvents can be

measured by a U-tube viscometerThe polymer solutions are allowed to stand

for 24 h prior to measurement to ensure

complete polymer dissolution



Standard USP or BP dissolution apparatus areused to study in vitro release profiles

Dissolution medium used for the study varied

from 100-500 ml and speed of rotation from50-100 rpm.

Dissolution medium is decided from the drug

being encapsulated



Targeted drug delivery to Peyer’s patch

Live cell encapsulation

Bioadhesive microparticles show enhanced oralbio availability of insulin, dicumarol

DNA vaccines with prolonged immunoresponses



Ansel,H.C., Pharmaceutical dosage form anddrug delivery system.

Lehman Leon, Lieberman A. Herbert and

KanigL.Josep. The Theory and Practice of IndustrialPharmacy

S.P.Vyas and R.K.Khar, Targeted

andControlled drug delivery

sarada mec 2.pptx

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