Microencapsulation
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Transcript of Microencapsulation
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Presented by: SAMIKSHA SAWANT M.Pharm (IP) 2nd SemGuided by: Dr. (Mrs.) INDIRA PARAB
MICROENCAPSULATION AND PARTICLE COATING
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History
Mr. Green made first gelatin microcapsules in 1940
It then took 9 years of research to make available marketed products
Technique of microencapsulation is adapted from nature itself
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What is microencapsulation?
Microencapsulation is a process by which individual particles or droplets of an active material are isolated by being surrounded with a coating to produce a microcapsule.
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Advantages of microencapsulatio
n
sustained/prolonged
drug releaseTaste/odour
masking
Stabilization to drugs
Preventing incompatibilit
y
Free flowing powder
form
Reduce toxicity/ GI irritation
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Reliable means to deliver the drug to the target site with specificity, if modified, and to maintain the desired concentration at the site of interest
without untoward effects.Solid biodegradable microspheres have the
potential throughout the particle matrix for the controlled release of drug.
Microspheres received much attention not only for prolonged release, but also for targeting of
anticancer drugs to the tumour.The size, surface charge and surface
hydrophilicity of microspheres have been found to be important in determining the fate of
particles in vivo.
Studies on the macrophage uptake of microspheres have demonstrated their
potential in targeting drugs to pathogens residing intracellularly
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It is an expensive process
Requires skill
Difficult to obtain continuous and uniform film
Disadvantages
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Formulation considerations• The solid core can be mixture of active
constituents, stabilizers, diluents, excipients and release-rate retardants or accelerators.
Core materials
• Compatible, non reactive with core material
• Provide desired coating properties like strength, flexibility, impermeability, optical properties, non hygroscopicity, tasteless and stable
Coating materials
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Water soluble resins – Gelatin, Gum Arabic,
Starch, Polyvinylpyrrolidone,
Carboxymethylcellulose,
Hydroxyethylcellulose, Methylcellulose,
Arabinogalactan, PVA etc.
Water insoluble resins – Ethylcellulose, Polyethylene,
Polymethacrylate, Polyamide (Nylon), Poly
(Ethylene Vinyl acetate),cellulose
nitrate, Silicones, etc.
Waxes and lipids – Paraffin, Carnauba,
Spermaceti, Beeswax, Stearic acid, Stearyl
alcohol, Glyceryl stearates.
Enteric resins – Shellac, Cellulose acetate phthalate, Zein.
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MICROENCAP-SULATION
TECHNIQUES
Chemical processes:
PolymerizationPolycondensation
Solvent evaporation
Physico-chemical processes:Coacervation
Supercritical CO2 assisted microencapsulationAnti gas solvency
Partial gas saturated solution
Physico-mechanical processes:
Spray drying and congealing
Air suspensionSpinning disc
technique jet cutter Vibrational nozzle
Extrusion technique
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Polymerization
A relatively new microencapsulation method utilizes polymerization techniques to form protective
microcapsule
The methods involve the reaction of monomeric units located at the interface
existing between a core material substance and a continuous phase in
which the core material is dispersed.
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Interfacial polymerisation
In- situ polymerisation
The multifunctional monomer dissolved in liquid core material which will be then dispersed in aqueous phase containing dispersing agent.
A co reactant multifunctional amine will be added to the mixture.
This results in rapid polymerization at interface and generation of capsule shell takes place.
A polyurea shell will be formed when isocyanate reacts with amine,
polynylon or polyamide shell will be formed when acid chloride reacts with amine.
In this process no reactive agents are added to the core material.
polymerization occurs exclusively in the continuous phase and on the continuous phase side of the interface formed by the dispersed core material and continuous phase.
Initially a low molecular weight prepolymer will be formed, as time goes on the prepolymer grows in size.
it deposits on the surface of the dispersed core material thereby generating solid capsule shell.
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PolymerizationSingle emulsion method
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Double emulsion method
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Solvent evaporation The process involves dissolving microcapsule coating
(polymer) in a volatile solvent A core material (drug) to be microencapsulated is
dissolved or dispersed in the coating polymer solution. With agitation, the core – coating material mixture is
dispersed in the liquid manufacturing vehicle phase to obtain appropriate size microcapsules.
Agitation of system is continued until the solvent partitions into the aqueous phase and is removed by evaporation.
This process results in hardened microspheres which contain the active moiety.
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Solvent evaporation
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Coacervation
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Pan coatingSuitable for large particles of size
greater than 600 microns.The particles are tumbled in a pan or
other device while the coating material is applied slowly
The coating is applied as a solution or as an atomized spray to the desired solid core material in the coating pan
Usually, to remove the coating solvent, warm air is passed over the coated materials as the coatings are being applied in the coating pans.
In some cases, final solvent removal is accomplished in drying oven.
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Air suspension technique• In this, the fine core
materials are suspended in a vertical current of air and sprayed with the coating material
• After evaporation of solvent, a layer of encapsulating material is deposited on core
• Gives improved control and flexibility as compared to pan coating
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Rapid expansion of Supercritical fluid
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Anti gas solvency Mix core and shell materials a
solvent which is miscible in supercritical fluid
Now add this to supercritical fluid at high pressure and agitation
This leads to super saturation such that precipitation of the solute occurs . Thus, the solute must be soluble in the liquid solvent, but should not dissolve in the mixture of solvent and supercritical fluid
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Particles from a gas-saturated solution • This process is carried out by mixing core and
shell materials in supercritical fluid at high pressure.
• During this process supercritical fluid penetrates the shell material, causing swelling.
• When the mixture is heated above the glass transition temperature the polymer liquefies.
• Upon releasing the pressure, the shell material is allowed to deposit onto the active ingredient.
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Spray drying and congealingDispersing the core material in a liquefied coating Substance /spraying or introducing the coating mixture on to core material.Coating solidification in spray drying is effected by rapid evaporation of a solvent in which the coating material is dissolved. Coating solidification in spray congealing method is accomplished by thermally congealing a molten coating material or by solidifying a dissolved coating by introducing the coating core material mixture into a non-solvent.
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Spinning disc methodSuspensions of core particles in liquid shell material are poured into a rotating disc.Due to the spinning action of the disc, the core particles become coated with the shell material.The coated particles are then cast from the edge of the disc by centrifugal force.After that the shell material is solidified by external means (usually cooling).This technology is rapid, cost-effective, relatively simple and has high production efficiencies.
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Vibration technologyThis is based on Rayleigh instability
A fluid stream of liquid core and shell materials is pumped through concentric tubes and forms droplets under the influence of vibration.
To guarantee production of uniform beads and to avoid large size distributions due to coalescence effects during the flight, the droplets pass through an electrostatic field to be charged
As a result these droplets do not hit each other during the flight
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Jet cutter technology• This is a simple technology for bead production that
meets the requirement of producing monodisperse beads originating from low up to viscous fluids with a high throughput
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Particle size
Capture efficiency
Density and bulk density
Viscosity of
polymeric solution
Angle of repose
Polymer solubility
in solvents
In vitro methods
Morphology
CHARACTERIZATION
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Applications Microencapsulation has been employed to provide
protection to the core materials against atmospheric effects, e.g., Vitamin A Palmitate.
Separation of incompatible substance has been achieved by encapsulation
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.
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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 e.g. Sodium chloride.
Carbon tetra chlorides and a number of other substances have been microencapsulated to reduce their odour and volatility
To reduce volatality of liquids like peppermint oil Helps to prepare SRDF and enteric coated products,
controlled release products Used to improve flow properties before compression
into tablets
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INJECTABLES:Smaller molecules can stay in the blood stream
longer with fewer side effectsLess frequent injectionMore sophisticated site targettingDecreased toxicity
BIOLOGICS:The harsh condition in the stomach denatures most
proteins and peptides hence they require some sort of depot or extended release can be done by microencapsulation.
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After hydrolysis in in the lower intestine, the polyunsaturated fats is digested and absorbed, thereby resulting in higher amounts of unsaturated fats in milk
and meat.
Polyunsaturated vegetable oil was encapsulated in protein core and reacted with formaldehyde, thus protecting the unsaturated fats from bacteria in
rumen.
Plant fat contains polyunsaturated fatty acids, but milk and meat contains only 2-4% of it
MICROENCAPSULATION FOR DECREASING ATHEROSCLEROSIS
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Recent studies• Hughes provided a method of sustained delivery of an
active drug to a posterior part of an eye of a mammal to treat or prevent a disease or condition affecting mammals. The method is comprised of administering an effective amount of an ester prodrug of the active drug such as tazarotene (prodrug of tazarotenic acid) subconjunctivally or periocularly since a systemic administration requires high systemic concentration of the prodrug. The ester prodrug is contained in biodegradable polymeric microparticle system prepared using the o/w emulsion solvent evaporation methods.
• Encapsulation of nucleotides and growth hormone using simple or double emulsification methods was achieved by Johnson et al
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• A method of encapsulating DNA retaining its ability to induce expression of its coding sequence in a microparticle for oral administration prepared using the w/o/w emulsion and using biodegradable polymers under reduced shear is produced by Jones et al
• Reslow et al. utilized starch to encapsulate vaccines using emulsification method. In process, an immunologically active substance (vaccine) is suspended in an aqueous starch solution with an amylopectin content exceeding 85% by weight. The starch droplets containing the vaccine are allowed to gel as the starch has capacity to gel naturally.
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Brand name API Manufacturer
OROS CT(osmotically active
tablets)
Colon specific drugs Alza corp.
ReGel(oncogel)
Paclitaxel Macro Med Inc.
Clopigrel clopidogrel+ Aspirin Lupin pinnacle
Clobitab clopidogrel+ Aspirin Lupin pinnacle
Atoplus Atorvastatin Triton (calyx)
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References• The Theory and Practice of Industrial Pharmacy,
lachman/lieberman, 4th edition, pg no. 579-596• Microencapsulation- Processes and Applications,
edited by Tan E. Vandegar, pg no. 1-20 and 57-59• Multiparticulate drug delivery, edited by Iisaac
Ghebre- Sellassie, pg no. 51-109• The Design and Manufacture of Medicines,
Michael Aulton and Kevin M.G.Taylor, 4th edition, pg no. 578-581
• Polymeric Drug Delivery- Particulate Drug Carriers, edited by Sonke Svenson, pg no. 242-245
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References• Microencapsulation: a vital technique in novel drug delivery system
P.Venkatesan, R.Manavalan and K.Valliappan (http://jpsr.pharmainfo.in/Documents/Volumes/Vol1Issue4/
jpsr01040903.pdf)• Microencapsulation: Process, Techniques and Applications Hammad
umer*1 , Hemlata Nigam2 , Asif M Tamboli2 , M. Sundara Moorthi Nainar2
(http://www.ijrpbsonline.com/files/R017.pdf) • Microencapsulation: a review jyothi sri.s* 1 , a.seethadevi 1 , k.suria
prabha 1 , p.muthuprasanna 1 and ,p.pavitra2 (http://ijpbs.net/vol-3/issue-1/bio/P%20-%2058.pdf)• Microencapsulation – A Novel Approach in Drug Delivery: A Review Nitika Agnihotri, Ravinesh Mishra*, Chirag Goda, Manu Arora (file:///C:/Users/B%20A%20Sawant/Downloads/IGPS_2_1.-Nitika-
Agnihotri-et-al-2012.pdf)
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References
• Reslow M, Bjorn S, Drustrup J, Gustafsson NO, Jonsson M, Laakso T, inventors. A controlled release, parenterally administrable microparticle preparation. EP1328258. 2008
(http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3093624/)
• Microencapsulation(https://uqu.edu.sa/files2/tiny_mce/plugins/
filemanager/files/4290121/MICROENCAPSULATION.pdf
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Thankyou