MICROENCAPSULATIONFACULTY GUIDE: PRESENTED BY:DR. MARYAM SARWAT ANSH DEV A4513309001
“ Micro encapsulation is at crossroadsof art, science and technology. Theright choice between process andchemistry, defining the processingconditions and parameters at a widerange of machines, is possible only forthose with a sound scientificbackground, combined with a longtime experience of trial and error.”
• It is the process of enclosing a core material inside a miniature capsule called microcapsules• It is a physic-chemical process, total surface area determines most of the time the wall thickness and as such the resistance of the micro capsule in its final application.
1. CORE MATERIAL: The substance that is encapsulated.2. COATING: The material encapsulating the core3. SHELLS: Microcapsules may have one wall or multiple shells arranged in strata of varying thicknesses around the core.
• In some cases to isolate the core from its surroundings isolating vitamins from the deteriorating effects of oxygen retarding evaporation of a volatile core improving the handling properties of a sticky material isolating a reactive core from chemical attack• Others not to isolate the core completely but to control the rate at which it leaves the microcapsule increasing the selectivity of an adsorption or extraction process
• CHEMICAL METHODS Coecervation Interfacial polymerization Phase separation In situ polymerization Centrifugal force processes• PHYSICAL METHODS Spray drying Fluid bed coating Centrifugal extrusion processes Spinning disk method
APPLICATION : Capsules for carbonless paper and for many other applications are producedSTEPS1. takes advantage of the reaction of aqueous solutions of cationic and anionic polymers such as gelatin and gum arabic.2. polymers form a concentrated phase called the complex coacervate. The coacervate exists in equilibrium with a dilute supernatant phase.
This technique is characterized by wall formation via therapid polymerization of monomers at the surface of thedroplets or particles core material, and this solution isdispersed in an aqueous phase.
This method utilizes two polymers that are soluble in acommon solvent; yet do not mix with one another in thesolution. FIGURE: PHASE SEPARATOR
In situ polymerization is a chemical encapsulation technique very similar to interfacial polymerization. The distinguishing characteristic of in situ polymerization is that no reactants areincluded in the core material.
Centrifugal force processes were developed in the 1940s to encapsulate fish oils and vitamins, protecting them from oxidation. This techniques is common for both chemical and physical techniques.
An emulsion is preparedby dispersing the corematerial, usually an oil oractive ingredientimmiscible with water;into a concentratedsolution of wall materialuntil the desired size of oildroplets are attained. Theresultant emulsion isatomized into a spray ofdroplets by pumping theslurry through a rotatingdisc into the heatedcompartment of a spraydrier.
Fluid bed coating, another mechanical encapsulation method,is restricted to encapsulation of solid core materials, includingliquids absorbed into porous solids. This technique is usedextensively to encapsulate pharmaceuticals.
The internal phase is dispersed into the liquid wallmaterial and the mixture is advanced onto a turningdisk. Droplets of pure shell material are thrown off ofthe rim of the disk along with discrete particles ofcore material enclosed in a skin of shell material.After having been solidified by cooling, themicrocapsules are collected separately from theparticles of shell material.
• Microorganism and enzyme immobilization• Protection against UV, heat, oxidation, acids, bases (e.g. colorants and vitamins).• Improved shelf life due to preventing degradative reactions (dehydration, oxidation)• Masking of taste or odours.• Improved processing, texture and less wastage of ingredients.• Handling liquids as solids• Enhance visual aspect and marketing concept.
• Microencapsulation is the packaging of small droplets of liquid or particles with a thin film.• The lowest particle size of microcapsules is 1µm and the largest size is 1mm.• Microcapsules consist of a core and a wall (or shell). The configuration of the core can be a spherical or irregular particle, liquid-phase suspended solid, solid matrix, dispersed solid and aggregates of solids or liquid forms.
APPLICATION OF MICROENCAPSULATION• To mask the bitter taste of drugs like Paracetamol, Nitrofurantoin etc.• To reduce gastric and other gastro intestinal (G.I) tract irritations, For eg., sustained release Aspirin preparations have been reported to cause significantly less G.I. bleeding than conventional preparations• A liquid can be converted to a pseudo-solid for easy handling and storage, eg. Eprazinone.• Hygroscopic properties of core materials may be reduced by microencapsulation eg. Sodium chloride.• Carbon tetra chlorides and a number of other substances have been microencapsulated to reduce their odor and volatility.
CONCLUSIONMicroencapsulation system offers potentialadvantages over conventional drug deliverysystems and also established as unique carriersystems for many pharmaceuticals (targeted drugdelivery systems). Although significant advanceshave been made in the field ofmicroencapsulation, still many challenges need to be rectified during the appropriateselection of core materials, coating materials and process techniques.