Microencapsulation Technologies IN NDDS.

UNIT II Microencapsulation Technologies.pdf

1. MICROENCAPSULATION
TECHNIQUES

2. Aprocessbywhichverytinydropletsor
particlesofliquidorsolidmaterialare
surroundedorcoatedwithacontinuous
filmofpolymericmaterial.
➢Particleshavingdiameterbetween3–800µmare
knownasmicro-particles.
➢Particleslargerthan1000µmareknownasMacro
particles.
Definition

3. Generallyconsistoftwocomponents
a)Core,internalphaseorfill
b)Shell,Coatormembrane.
Core material
Shell material

4. CLASSIFICATION:
1.Microcapsules:Theactiveagentformsacoresurroundedbyaninert
diffusionbarrier.
2.Microspheres:Theactiveagentisdispersedordissolvedinaninertpolymer.

5. ADVANTAGES:
✓ToIncreaseofbioavailability
✓Toalterthedrugrelease
✓Toimprovethepatient’scompliance
✓Toproduceatargeteddrugdelivery
✓Toreducethereactivityofthecoreinrelation
totheoutsideenvironment
✓Todecreaseevaporationrateofthecore
material.
✓Toconvertliquidtosolidform&
✓Tomaskthecoretaste.

6. FUNDAMENTAL CONSIDERATION :
Corematerial Coatingmaterial Vehicle
Solid Liquid
Microencapsulation
Polymers
Waxes
Resins
Proteins
Polysaccharides
Aqueous Non-aqueous

7. MICROENCAPSULATION TECHNIQUES:
Physical Methods:
➢Air suspension techniques (Wurster)
➢Coacervation Process
➢Spray Drying & Congealing
➢Pan Coating
➢Solvent Evaporation
➢Polymerization
➢Extrusion
➢Single & Double Emulsion Techniques
➢Supercritical fluid Anti Solvent method (SAS)
➢Nozzle Vibration Technology
Chemical Methods:
➢Interfacialpolymerization
➢In-situpolymerization
➢Matrixpolymerization

8. AIR SUSPENSION TECHNIQUES (WURSTER) PROCESS:
Inthisprocess,thedrugparticlesarecoatedand
driedwhilesuspendedinanupwardlymoving
currentofair.
Solutionsandsuspensionsofcoatingmaterialsin
bothwaterandvolatileorganicsolventsare
employed.
Thedryingofthecoatedparticlesisaccomplished
ateitherroomorelevatedtemperatures,
dependingonthesolventused.

10. COACERVATION / PHASE SEPARATION
Threestepsprocess.
Step1:Formationofthreeimmisciblechemicalphases
(i)aliquidmanufacturingvehiclephase,(ii)acorematerialphase
and(iii)acoatingmaterialphase.
Thecorematerialisdispersedinasolutionofthecoatingpolymer,
thesolventforthepolymerbeingtheliquidmanufacturingvehicle
phase.Thecoatingmaterialphase,animmisciblepolymerina
liquidstate,isformedbyutilizingoneofthemethodsofphase
separationcoacervation,thatis,
➢Bychangingthetemperatureofthepolymersolution
➢Byaddingasalt
➢Byaddinganon-solvent
➢Byaddingincompatiblepolymertothepolymersolution
➢Byinducingapolymer-polymerinteraction.

11. COACERVATION / PHASE SEPARATION
Step2:Depositingtheliquidpolymercoatinguponthe
corematerial
Thisisaccomplishedbycontrolled,physicalmixingofthecoating
material(whileliquid)andthecorematerialinthemanufacturing
vehicle.
Depositionoftheliquidpolymercoatingaroundthecorematerial
occursifthepolymerisadsorbedattheinterfaceformedbetween
thecorematerialandtheliquidvehiclephase.
Step3:Rigidizingthecoating
Thisisusuallydonebythermal,crosslinkingordesolvation
techniques,toformaselfsustainingmicrocapsule.

12. Polymeric
Membrane
Droplets
Homogeneous
Polymer Solution
Coacervate
Droplets
PHASE
SEPARATION
MEMBRANE
FORMATION
1.Formationofthreeimmisciblephase2.Depositionofcoating
3.Rigidizationofcoating.

13. COMPLEX COACERVATION :

14. Polymer
+ Volatile organic solvent
Organic Polymeric Phase
Formation of Oil-in-Water
Emulsion
Solvent Evaporation
Particle Formation by
Polymer
Precipitation
RECOVERY OF POLYMERIC
MICROPARTICLES
Temperatureincrease
Active
Ingredient
Addition into an aqueous
phase (+o/w stabilizer)
SOLVENT EVAPORATIONS
Step1:
Formationofasolution/dispersion
ofthedrugintoanorganicpolymer
phase.
Step2:
Emulsificationofthepolymerphase
intoanaqueousphasecontaininga
suitablestabilizer,thus,forminga
o/wemulsion.
Step3:
Removaloftheorganicsolventfrom
thedispersedphasebyextraction
orevaporationleadingtopolymer
precipitationandformationofthe
microspheres.

15. SPRAY DRYING & CONGEALING ( COOLING)
Spray drying : Spray = Aqueous Solution/ Hot Air
Spray congealing : Spray = Hot Melt / Cold Air

16. 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
Monodisoerse Latex
Formation by Polymer
Precipitation
RECOVERY OF POLYMERIC
MICROPARTICLES
➢Mono-dispersemicro-gelsin
themicronorsubmicronsize
range.
➢Precipitationpolymerization
startsfromahomogeneous
monomersolutioninwhichthe
synthesized polymer is
insoluble.
➢Theparticlesizeofthe
resultingmicrospheresdepends
on the polymerization
conditions,includingthe
monomer /comonomer
composition,theamountof
initiatorandthetotalmonomer
concentration.
POLYMERIZATION:

17. EXTRUSION:
➢Thismethodwasfirstpatentedin1957.
➢Theadvantageofextrusionisthatitcompletely
surroundsthecorematerialwithwallmaterial.
➢Theprocessinvolvesforcingacorematerialdispersed
inamoltencarbohydratemassthroughaseriesof
dies,intoabathofdehydratingliquid.
➢Whencontactwiththeliquidismade,the
carbohydratecasehardenstoentrapthecore
material.
➢Theextrudedfilamentsareseparatedfromtheliquid
bath,driedusingananti-cakingagentsuchascalcium
tri-polyphosphateandsized.
➢Thisprocessisparticularlyusefulforheatlabile
substancessuchasflavours,vitamin-Candcolours.

18. SINGLE EMULSION TECHNIQUE :

19. DOUBLE EMULSION TECHNIQUES :

20. NOZZLE VIBRATION TECHNOLOGY :

21. Thesolidisdissolvedinaconventionalsolvent.The
solutionisintroducedintoasupercriticalfluid(mostly
CO
2andwater(anti-solvent)leadingtoarapidvolume
expansionofthesolution.Asaresult,thesolvent
poweroftheconventionalsolventdecreasesandsuper-
saturationtriggersofftheprecipitationofparticles.
Afterthesolidhasprecipitatedoutfreshanti-solventis
addedtoflushawaythesolvent.
SAS METHOD :

22. SAS METHOD :

23. Interfacialpolymerization
Apolymerizationreactionthatoccursatornear
theinterfacialboundaryoftwoimmiscible
solutions.Thisinvolvesdispersinganorganic
phase(containingpoly-functionalmonomers
and/oroligomers)intoanaqueousphase
(containingamixtureofemulsifiersandprotective
colloidstabilizers)alongwiththematerialtobe
encapsulated.
Theresultingoil-in-wateremulsionundergoes
interfacialpolymerization,withthemonomers/
oligomersreactingspontaneouslyatthephase
boundarytoformmicrocapsulepolymerwalls.

24. Microcapsule manufacture by interfacial polymerisation.

25. In-situpolymerization
Inthisprocessdirectpolymerizationofasinglemonomeriscarriedouton
theparticlesurface.Inoneprocess,e.g.Cellulosefibersareencapsulatedin
polyethylenewhileimmersedindrytoluene.Usualdepositionratesare
about0.5μm/min.Coatingthicknessranges0.2-75μm.Thecoatingis
uniform,evenoversharpprojections.
Matrixpolymerization
Thecorematerialisimbeddedinapolymericmatrixduringformationofthe
particles.Asimplemethodofthistypeisspray-drying,inwhichtheparticle
isformedbyevaporationofthesolventfromthematrixmaterial.However,
thesolidificationofthematrixalsocanbecausedbyachemicalchange.

26. APPLICATION OF MICROENCAPSULATION TECHNIQUES: