coacervation-phase separation technique in micro encapsulation

Micro encapsulation

1. COACERVATION- PHASE SEPERATION TECHNIQUE IN MICROENCAPSULATION By: N. Sivanaga Tejaswini Y14PH0505 CLPT

2. CONTENTS… Introduction Microencapsulation techniques Coacervation-phase separation process Steps in coacervation-phase separation Techniques used in coacervation-phase separation Conclusion References

3. INTRODUCTION: Microencapsulation is the packaging of small particles of solid, liquid or gas, also known as core , within a secondary material, also known as shell or coating to form small microparticles.

4. MICROENCAPSULATION TECHNIQUES: Air suspension process Coacervation-phase separation process Pan coating Solvent evaporation process Spray drying or Spray congealing Interfacial polymerization Multi orifice centrifugal process.

5. COACERVATION-PHASE SEPARATION PROCESS: Coacervation means the separation of a liquid or phase when solution of two hydrophilic colloids are mixed under suitable conditions. In this method, the three immiscible phases of core material, solvent and coating material are formed followed by deposition of coating material on the core. The coating material is dissolved in a suitable solvent and the core material is uniformly dispersed in the solution of the coating material. Then the coating material is phased out of its solution which starts getting deposited on the particles of the core material.

6. STEPS IN COACERVATION: Coat formation during coacervation-phase separation process consists of three steps carried out under continues agitation: STEP:1 Formation of three immiscible chemical phases (vehicle, core and liquid coating). STEP:2 Deposition of the coat material STEP:3 Rigidisation of the coat material.

7. STEP:1 Formation of three immiscible phases A Liquid manufacturing vehicle phase, a core material phase and a coat material phase. To form the three phases, the core material is dispersed in a solution of the coating polymer, the solvent for the polymer being the liquid manufacturing vehicle phase. The coating material phase, an immiscible polymer in a liquid state, is formed by utilizing one of the methods of coacervation phase separation.

8. STEP:2 Deposition of the coating material: This is accomplished by controlled, physical mixing of the coating material and the core material is the manufacturing vehicle, Deposition of the liquid polymer coating around the core material occurs if the polymer is adsorbed at the interface formed between the core material and the liquid vehicle phase, and this adsorption phenomenon is a prerequisite for the coating. The continued deposition of the coating material is promoted by a reduction in the total free interfacial energy of the system, by decreasing of the coating material surface area during coalescence of the liquid polymer droplets.

9. STEP:3 Rigidisation of the coating material The process involves rigidizing the coating usually by thermal, crosslinking or desolvation technique to form a self-sustained microcapsule.

10. TECHNIQUES USED IN COACERVATION Temperature change Incompatible polymer addition Non-solvent addition Salt addition Polymer polymer interaction

11. TEMPERATURE CHANGE Under proper polymer concentration, temperature and agitation conditions the liquid polymer droplets coalesce around the dispersed core material particles, thus forming the embryonic microcapsules. EXAMPLE: C ore material : N- amino acetophenol C oating material : Ethyl cellulose S olvent : Cyclohexane

12. INCOMPATABLE POLYMER ADDITION Liquid phase separation of a polymeric coating material and microencapsulation can be accomplished by utilizing the incompatibility dissimilar polymers existing in a common solvent. EXAMPLE: C ore material: Methylene blue HCL C oat material: Ethyl cellulose S olvent : Toulene

13. NON-SOLVENT ADDITION A Liquid that is a non-solvent for a given polymer is added, to a solution of the polymer to induce the phase separation, as indicated by the general phase diagram. The resulting immiscible, liquid polymer can be utilized to microencapsulation of an immiscible core material. EXAMPLE: C ore material: Methylscoplamine Coat material: Cellulose acetate Solvent : Methyl ethyl ketone N on-solvent : Isopropyl ether

14. SALT ADDITION Soluble inorganic salts are added to aqueous solutions of water soluble polymers to cause phase separation. EXAMPLE: Core material: Vitamin A Coat material: Pig gelatin Salt : Sodium sulphate Solvent : Water

15. POLYMER-POLYMER INTERACTION (COMPLEX COACERVATION) The interaction of oppositely charged poly electrolytes can result in the formation of a complex having reduced solubility and phase separation occurs. Complex coacervation process consists of three steps: Formation of an O/W emulsion Formation of the coating Stabilization of the coating. EXAMPLE: Core material: Methyl salicylate Coat material: Gelatin or Gum acacia Solvent : Water

16. CONCLUSION: Microencapsulation process involves basic understanding of the general properties of microcapsules such as nature of the core and the coating material, the stability and the release characteristics of the coated materials and its methods. Microencapsulation technique is employed for the production of: Sustained release or prolonged action of medications. Taste masked chewable tablets, suspensions and powders. Stabilization of oxidation process. Reduction of volatility. Reduced gastric irritation. Also a newer formulation concept of creams, ointments, aerosols and suppositories were employed.

17. REFERENCES: “ The Theory And Practice Of Industrial Pharmacy” , by Leon Lachman and Herbert Liebermann ; 3 rd edition, Indian Edition; Varghese Publishing House, Bombay; 1987; Page No: 412-429 http://www.google.com