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Micro capsules or microspheres

This document provides an in-depth overview of microspheres, which are small spherical particles made from biodegradable materials and used in drug delivery systems. It discusses various types of microspheres, their advantages and disadvantages, classification, preparation methods, and applications including ocular, oral, and transdermal drug delivery. Additionally, it explains the evaluation of microspheres through various analyses to assess particle attributes and drug entrapment efficiency.

Education◦
Presented by P.Pavazhaviji M.Pharm I Year (II Sem) Dept. of Pharmaceutics MTPG & RIHS Puducherry 1
MICROSPHERES  Microspheres are small spherical particles, ranging in size from 1 μm to 1000 μm.  They are spherical free flowing particles consisting of proteins or synthetic polymers which are biodegradable in nature. 2
CLASSIFICATION Microspheres Microcapsules Micromatrices  Microcapsules consisting of an encapsulated core particle .  Micromatrices in which entrapped substance is dispersed throughout the matrix. 3
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ADVANTAGES  Improve bioavailability  Provide prolonged therapeutic effect.  Provide constant drug concentration in blood .  Decrease toxicity.  Protect the drug from enzymatic and photolytic cleavage  Reduce the dosing frequency and thereby improve the patient compliance 5
DISADVANTAGES  The cost is more.  Process conditions like change in temperature, pH, solvent addition, and evaporation/agitation may influence the stability of core particles.  Degradation of product due to heat, hydrolysis, oxidation, solar radiation or biological agents. 6
TYPES OF MICROSPHERES  Bioadhesive microspheres  Floating microspheres  Radioactive microspheres  Magnetic microspheres  Polymeric microspheres a) Biodegradable polymeric microspheres b) Synthetic polymeric microspheres 7
Bio-adhesive microspheres:  Adhesion of drug delivery device to the mucosal membrane such as buccal, ocular, rectal, nasal etc can be termed as Bioadhesive microspheres . 8 TYPES OF MICROSPHERES
Magnetic microspheres:  This kind of delivery system is very much important which localises the drug to the disease site.  Magnetic carriers receive magnetic responses to a magnetic field from incorporated materials that are used for magnetic microspheres. 9 TYPES OF MICROSPHERES
Floating microspheres:  In floating types the bulk density is less than the gastric fluid and so remains buoyant in stomach. 10 TYPES OF MICROSPHERES
Radioactive microspheres:  radioactive microspheres deliver high radiation dose to the targeted areas without damaging the normal surrounding tissues. 11 TYPES OF MICROSPHERES
Polymeric microspheres:  The different types of polymeric microspheres can be classified as follows: a) Biodegradable polymeric microspheres b) Synthetic polymeric microspheres 12 TYPES OF MICROSPHERES
METHOD OF PREPARATION  Single emulsion technique  Double emulsion technique  Solvent evaporation  Phase separation coacervation technique  Spray drying and spray congealing  Solvent extraction  Polymerization 13
 SINGLE EMULSION TECHNIQUE 14 Polymer in aqueous solution+ drug Disperse in organic phase (oil/ chloroform) Microspheres Microspheres in organic phase stir or sonicate Chemical cross linking or heat denaturation Centrifugation , Wash, separation
 DOUBLE EMULSION TECHNIQUE 15 Polymer in aq. solution + Drug Disperse in organic phase First emulsion ( W/O) Multiple emulsion(W/O/W) Microspheres in solution Microspheres Homogenization or sonication Addition of aq. sol of PVA Addition to large aq. Phase Separation, wash, dry
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 SOLVENT EVAPORATION 17 Coating polymer solution Core material disperse in liquid manufacturing vehicle phase Evaporation of polymer solvent Microspheres Core material Dissolved or dispersed Agitation Heating (if need)
 PHASE SEPARATION COACERVATION TECHNIQUE 18 Aq/ organic solution of polymer Drug dispersed or dissolved in the polymer solution Polymer rich globules Microspheres in aq/ organic phase microspheres Add drug Phase separation induced by different means solidify Separate, wash and dry
Steps of coacervation Formation of three immiscible chemical phases Deposition of the coating Rigidization of the coating 19
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Techniques used for coacervation  Change in temperature  Incompatible polymer addition  Non solvent addition  Salt addition  Polymer – polymer interaction 21
 SPRAY DRYING AND SPRAY CONGEALING 22 Polymer dissolved in organic phase (acetone) Drug is dispersed in polymer solution under high speed homogenization/ Atomized in a stream of hot air Separated by cyclone separator and traces of solvent is removed by vacuum drying microspheres Solvent evaporation Formation of small droplets
23  SOLVENT EXTRACTION
 POLYMERIZATION 24 polymerization normal interfacial Emulsion polymerization Suspension polymerization Bulk polymerization
i. a ) BULK POLYMERIZATION 25 Monomer / mixture of monomer + initiator Microspheres Heated to initiate polymerization Polymer obtained is moulded / fragmented
i. b ) SUSPENSION POLYMERIZATION 26 Monomer or composition of monomers are heated and dispersed in water Microspheres Droplets (vigorous agitation)
i. c) EMULSION POLYMERIZATION 27 Monomer + aq. Solution of NaOH + initiator ( stir) Polymerization occurs , microspheres are formed Micelles solution of polymer in aq. medium
ii. INTERFACIAL POLYMERIZATION 28 Monomer A + water Oil phase W/O emulsion Add monomer B Microspheres in aq. Medium Microspheres High pressure homogenization polymerization
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EVALUATION OF MICROSPHERES 1 .Particle size and shape:  The most widely used procedures to visualize microparticles are conventional light microscopy (LM) and scanning electron microscopy (SEM). 2. surface chemistry :  The surface chemistry of the microspheres can be determined using the electron spectroscopy for chemical analysis(ESCA). 30
3) Drug entrapment efficiency:  Drug entrapment efficiency can be calculated using following equation, % Entrapment = Actual content / Theoretical content x 100 31
4) Swelling index : Swelling index can be calculated by using Swelling index= (mass of swollen microspheres –mass of dry microspheres) 100/mass of dried microspheres 32
5 )In vitro methods:  Release studies for different type of microspheres are carried out by using phosphate buffer pH 6.8, mostly by rotating paddle apparatus. 6) Adhesion property:  Freshly cut piece of pig intestine is used (5 cm long) to determine the adhesion property of Bio-adhesive microspheres. 33
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APPLICATIONS Ophthalmic Drug Delivery Oral drug delivery  Gene delivery Nasal drug delivery  Buccal drug delivery  Gastrointestinal drug delivery  Transdermal drug delivery Colonic drug delivery 35
MICROCAPSULES Microcapsules : Microcapsules consisting of an encapsulated core particle . Entrapped substance completely surrounded by a capsule distance wall. 36
MICROENCAPSULATION  “Microencapsulation may be defined as the process of surrounding or enveloping one substance within another substance on a very small scale, yielding capsules ranging from less than one micron to several hundred microns in size.”  It is mean of applying thin coating to small particle of solid or droplet of liquid & dispersion.  Particle size: 50-5000 micron. 2 phases:  a) Core material  b) Coating material 37
TECHNIQUES TO MANUFACTURE Physical methods  Air-suspension coating  Multiorifice centrifugal process  Pan coating  Coacervation Process  Spray–drying Chemical process  Solvent Evaporation  Polymerization 38
AIR SUSPENSION (WURSTER METHOD) 39 Within the coating chamber, particles are suspended on an upward moving air stream. Spraying of coating material on the air suspended particles. The cyclic process is repeated depending upon purpose of microencapsulation. Air stream serves to dry the product the core material receives an increment of coating material
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B) Pan Coating 41 The particles are tumbled in a pan while the coating material is applied slowly as solution or atomized spray to the core To remove the coating solvent, warm air is passed over the coated materials
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43 the rotating disc flings the particulate core material ( liquid) droplets or solid particles towards orifices The counter rotating disc mounted within the cylinder , atomizes or disperses the core material fed through the centrally located inlet . When the core material arrives at the orifices & encounters the coating material membrane The impact & centrifugal force , generated by the rotating cylinder , hurls the core material through the enveloping coating membrane. MULTIORIFICE CENTRIFUGAL PROCESS
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APPLICATION  For sustained or prolonged drug release.  For masking taste and odor of many drugs to improve patient compliance.  For converting liquid drugs in a free flowing powder.  To reduce toxicity and GI irritation  Incompatibility among the drugs can be prevented by microencapsulation.  The drugs, which are sensitive to oxygen, moisture or light, can be stabilized by microencapsulation 45
REFERENCE  Theory and practice in novel drug delivery system by S.P. VYAS.  MICROSPHERES: A BRIEF REVIEW Kadam N. R. and Suvarna V Department of Quality Assurance, SVKM’s Dr. Bhanuben Nanavati College of Pharmacy,Vile Parle, Maharashtra.  Leon, Lachman, Herbert A. L., Joseph, L. K; “ The Theory And Practice Of Industrial Pharmacy”, 3rd edition, 1990, Varghese Publishing House,412, 428. 46
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