Microencapsulation

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(Anurag Pandey) B.Pharm
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1. MICROENCAPSULATION PRESENTED BY :_ MR. ANURAG PDY (B.PHARM) SUBMITTED TO :_ MR.VIPIN AGARWAL ASSOCIATE PROFESSOR AT (INVERTIS INSTITUTE OF PHARMACY)

2. INTRODUCTION It is a process by which solids, liquids or gases can be enclosed in microscopic particles by formation of thin coating of wall material (polymer) around the substance. Also known as microcapsule, microsphere, coated granules, pellets. Particle size: 50-5000 micron. 2 phases: a) Core material b) Coating material

3. Core & coating materials CORE MATERIALS :_ The core material is the specific material to be coated. It can be liquid or solid in nature. E.g., acetaminophen, activated charcoal, aspirin, urease, potassium chloride, vitamin palmitate etc. 2. COATING MATERIALS :_ Selection of coating materials decides the physical & chemical properties of the resultant microcapsule/microsphere. E.g., Water soluble resins :- gelatin, starch, polyvinyl alcohol, polyacrylic acid, hydroxymethylcellulose etc. Water Insoluble resins :- ethyl cellulose, polyethylene, polymethcrylate, cellulose nitrate etc. Waxes & lipids :- Paraffin, stearic acid, stearyl alcohol etc. Enteric Resins :- Shellac, cellulose acetate pthalate (CAP) , zein etc .

4. Types of Microcapsule 1- Mononuclear :_ Mononuclear (core-shell) microcapsule contain the shell around the core. 2- Polynuclear:_ Polynuclear capsules have many cores enclosed within the shell. 3- Matrix :_ Matrix encapsulation in which the core materials is distributed homogeneously into the shell material.

5. To obtain maximum therapeutic efficacy drug is to be delivered :- To the target tissue : In the optimal amount : In the right period of time : there, by it causes little toxicity & minimal side effect Microencapsulation overcome some of the problems of conventional therapy & enhance the therapeutic efficacy of a given drug.

6. IMPORATANCE OF MICROENCAPSULATION Isolation of core from it’s surrounding as in isolating vitamins from the deteriorating effect of oxygen. Retarding evaporation of a volatile core. Improving the handling properties of a sticking material. Isolating a reactive core from chemical attack. For controlled release of drugs. Masking the taste or odour of the core like., Paracetamol, Nitrofurantoin etc. To reduce toxicity & G.I irritation. For converting liquid drugs in a free flowing powder. To get targeted release of the drug. Hygroscopic properties of core materials may be reduced by microencapsulation e.g., sodium chloride.

7. Table :_ Microencapsulation Process & their applicable core material   S.no   Microencapsulation Process   Applicable core material Approximate Particle size (µm)  1.  Air Suspension Solids 35-5000  2. Coacervation-phase separation Solids and Liquids 2-5000  3.  Multiorifice centrifugal Solids and Liquids  1-5000  4. Pan Coating Solids  600-5000  5. Solvent Evaporation Solids and Liquids  5-5000  6. Spray Drying and Congealing Solids and Liquids  600

8. Manufacturing techniques of Microencapsulation 1. PHYSICAL METHODS Spray drying Pan Coating Air-Suspension Coating Multi orifice – Centrifugal Process Spray Congealing Solvent Evaporation 2. PHYSIO-CHEMICAL METHODS Coacervation Process Polymerization Complex

9. COACERVATION PHASE INVERSION Coacervate means a cluster of droplets separated out of a lyophilic colloid's . THREE MAJOR STEPS :_ Formation of 3 immiscible chemical phase Deposition of coating Rigidization of coating. Formation of 3 immiscible chemical phase A liquid manufacturing vehicle phase, a core material phase and a coating material phase is formed by dispersing the core material in a solution of coating polymer, Coacervation is done by changing the temperature of the polymer solution; or by addition of a salt, or a non-solvent , or incompatible polymer to polymer solution; or by inducing polymer-polymer interaction. 2. Deposition of coating T he deposition takes place when the polymer is adsorbed at the interface between the liquid polymer and the core material 3. Rigidization of coating . Coating is made rigid by : Temperature Cross-linking D esolvation .

10. Fig., COACERVATION PHASE INVERSION

11. AIR SUSPENSION TECHNIQUE Solid , particulate core materials are dispersed in a supporting air stream. The coating material is sprayed on the air suspended particles. Within the coating chamber, particles are suspended on an upward moving air stream 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 . 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. 7 . Until the core material particles are thoroughly encapsulated. The supporting air stream also serves to dry the product while it is being encapsulated 9 . Drying rates are directly related to the volume temperature of the supporting air stream.

12. Fig., Air Suspension Technique Schematics of a fluid-bed coater. (a) Top spray; (b) bottom spray; (c) tangential spray

13. The coating solidification effected by rapid evaporating of solvent in which coating material is dissolved Approximate particle size :- About 600 micrometer SPRAY DRYING The coating solidification is effected by thermally congealing a molten coating material. The removal of solvent done by sorption extraction or evaporation technique SPRAY CONGEALING

14. MULTIORIFICE-CENTRIFUGAL PROCESS It is a mechanical process for producing microcapsules. Centrifugal forces are used to hurl a core material particle through an enveloping microencapsulation membrane . Processing variables include : The rotational speed of the cylinder , The flow rate of the core and coating materials , The concentration, viscosity, surface tension of the core material. The multi-orifice 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 - dry powder. Production rates of 50 to 75 pounds per hour .

15. Solid particle greater than 600 micron size are generally consider for effective coating. It is used for preparation of controlled- release beads. Coating is applied as solution by atomized spray to desired solid core material in coating pan. Usually warm air is passed over the coated material as the coating are being applied in the coating pan. PAN COATING

16. (Core material) (Dissolved Or Dispersed) Coating polymer solution (With Agitation) Liquid Manufacturing Vehicle Phase Heating (If necessary) Evaporation of Polymer solvent (Microencapsulation) Solvent Evaporation

17. 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. POLYMERIZATION COMPLEX EMULSION

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