multiple emulsions ppt

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ASSIGNMENT ON TOPIC: MULTIPLE EMULSIONS SUBMITTED TO: PROFESSOR Dr. NAZAR MOHAMMAD RANJHA BY AQSA AFZAL PHP -15 2010 JAVARIA SAEED PHP – 20-2010

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CONTENTS INTRODUCTION TYPES OF MULTIPLE EMULSIONS PREPARATION OF MULTIPLE EMULSIONS FORMULATION OF MULTIPLE EMULSIONS EVALUATION OF MULTIPLE EMULSIONS STABILITY OF MULTIPLE EMULSIONS APPLICATIONS CONCLUSION REFERENCES

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INTRODUCTION: Emulsions may be described as heterogeneous systems, where one immiscible liquid is dispersed in another in the form of droplets and stabilized by a third component called emulsifying agent The emulsions can be divided up into two Types : Oil in water (O/W) emulsions Water in Oil (W/O) emulsions.

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TYPES OF EMULSION: 1).simple emulsions (macro emulsions) Oil-in-water (o/w) water-in-oil (w/o) 2).multiple emulsions oil-in-water-in-oil (o/w/o) water-in-oil-in-water (w/o/w) 3).micro emulsions

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A . Macro emulsions (Simple Emulsions) 1).Oil in water (o/w) : Oil droplets are dispersed in a continuous aqueous phase. This emulsion is generally formed if the aqueous phase constitutes more than 45 % of the total weight and a hydrophilic emulsifier is used. These are [referred for oral administration and cosmetics . these are useful as water washable drug bases .The globule size is 0.25 to 10 microns. aqueous phase oil drop

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ii. Water in oil (w/o) : Aqueous droplets are dispersed in continuous oily phase. . This emulsion is generally formed if the oily phase constitutes more than 45 % of the total weight and a lipophilic emulsifier is used. These are used for cosmetics. The are employed for treatment of dry skin and emollient applications. Oil phase Aqueous phase

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MULTIPLE EMULSIONS Multiple emulsions are complex systems in which the dispersed phase contain smaller droplets inside. They are a type of poly dispersed systems where both oil-in-water & water-in-oil emulsions exist simultaneously. This is made possible by double emulsification hence the systems are also called as “Double emulsions ”.

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Multiple emulsions are thermodynamically unstable. They are often stabilized by using a combination of hydrophilic & hydrophobic surfactants. The ratio of these surfactants is important in achieving stable multiple emulsions These are also called as “Liquid membrane systems” as the liquid film which separates the liquid phases acts as a thin semipermeable film through which solute must diffuse in order to transverse from one phase to another .

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CLASSIFICATION: With optical microscopy method, multiple emulsions are classified as , 1 . coarse: (>3 micrometer in diameter ) 2 . Fine: (1-3 micrometer in diameter) 3 . Micro-multiple emulsions: (<1 micrometer in diameter)

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TYPES OF MULTIPLE EMULSIONS: 1).Water/Oil/Water (w/o/w) 2).Oil/Water/Oil (o/w/o)

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Water/Oil/Water (w/o/w) multiple emulsions consist of dispersed oil globules containing smaller aqueous droplets; each inner aqueous droplet is separated from the outer aqueous phase by an oil phase layer. The presence of at least two surfactants is required. One of them is predominantly Lipophilic for stabilizing the primary w/o emulsion & the other is Hydrophilic for the secondary o/w emulsion. 1).WATER/OIL/WATER (W/O/W ):

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2).OIL/WATER/OIL(O/W/O): Oil-in-water-in-oil (o/w/o) multiple emulsions contain an inner oil phase, a water phase, and outer oil phase. The inner oil phase is first dispersed in water to form an oil-in-water (o/w) emulsion. Then the o/w emulsion is further dispersed in the outer oil phase to form the o/w/o type multiple emulsion.

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Advantages : 1). A remarkable degree of Biocompatibility 2).Complete biodegradability 3).hydrophilic as well as Hydrophobic drugs can be entrapped 4 ).protection from inactivation by the endogenous factors 5)Increase in drug dosing intervals Masking the bitter taste of drugs

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Disadvantages : 1 ).Emulsion have short shelf life 2).These dosage forms are packed in a plastic or glass container So care should be taken in handling and storage

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Methods of Preparation : Multiple emulsions can be prepared by any of the numerous methods for the preparation of conventional emulsion system including sonication, agitation, and phase inversion. For the preparation of multiple emulsions two different surfactants of opposite nature are used. One surfactant stabilize the w/o(lipophilic) emulsion while the other stabilize the o/w hydrophilic emulsion. Emulsifying agents are adsorbed at the surface of droplets during emulsion formulation and prevent them from drawing close enough to aggregate.

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Different techniques used for the preparation of Multiple Emulsions: Two step emulsification technique, Modified two step emulsification Phase inversion technique, (One Step Technique) Membrane Emulsification Technique ,

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1).Two Steps Emulsification (Double Emulsification ): It is the most common method because it is very easy and gives high yield with reproducibility . This method involve re-emulsification of primary W/O or O/W emulsion using a suitable emulsifying agents. The first step involves the preparation of primary emulsions either o/w or w/o type which is then re-emulsified with an excess of aqueous phase or oil phase in the presence of second emulsifier. The finally prepared emulsion could be W/O /W or O/W/O respectively.

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Generally two emulsifier are used in the preparation of multiple emulsions. One is the lipophilic surfactant and other is hydrophilic surfactant. The first step-that is, the preparation of the primary emulsion-is usually carried out in a high-shear device to produce a very fine droplets. The second emulsification step is carried out in a low- shear device to avoid rupturing the multiple droplets.

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The primary W/O emulsion was prepared by adding an aqueous solution containing sodium salicylate to a Span 83 solution in light mineral oil at an equal volume ratio and stirring with a magnetic mixer (1000 rpm) for 15 minutes. The concentration of Span 83( sorbiton sesquioleate ) in light mineral oil varied from 0.1% to 40% wt /vol. In second step, the W/O primary emulsion was re-emulsified in a Tween 80 solution containing concentrations of Tween 80 from 0.1% to 10% wt / vol at an equal volume ratio and stirred for 5 minutes at 600 rpm to produce the W/O/W multiple emulsion. EXAMPLE:

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2).Modified Two Steps Emulsification : This method is different from conventional two step technique in two points Sonication and stirring are used to obtain fine, homogenous and stable o/w emulsion. Continuous phase is poured into a dispersed phase for preparing w/o/w emulsion. This method gives high yield and stable emulsion .

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3). Phase Inversion Technique (One Step Technique ): An increase in volume concentration of dispersed phase may cause an increase in the phase volume ratio, which subsequently leads the formation of multiple emulsions. The method typically involves the addition of an aqueous phase contains the hydrophilic emulsifier to an oil phase consisted of liquid paraffin and containing lipophilic emulsifier (Span 80). A well-defined volume of oil phase is placed in a vessel of pin mixer .

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An aqueous solution of emulsifier is then introduced successively to the oil phase in the vessel at a rate of 5 ml/min, while the pin mixer rotates steadily at 88 rpm at room temperature. When volume fraction of the aqueous solution of hydrophilic emulsifier exceeds 0.7, the continuous oil phase is substituted by the aqueous phase containing a number of the vesicular globules among the simple oil droplets, leading to phase inversion and formation of W/O/W multiple emulsion.

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MEMBRANE EMULSIFICATION TECHNIQUE This method uses low shear forces to produce emulsions. A porous glass membrane with controlled and homogenous pores is used in this method. Particle size of the emulsion can be controlled with the proper selection of the porous glass membrane. This is based on the use of microspores with a very narrow pore size distribution on the membrane. The phase which is to be dispersed is pressed through membrane pores

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The droplets formed at the membrane surface are detached by the continuous external aqueous phase flowing across the membrane surface. To support the emulsification and prevent coalescence of droplets, a surface active compound must be added to the continuous phase It can be successfully applied to make multiple emulsions as drug delivery systems

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The relation between membrane pore size and particle size of W/O/W emulsion exhibits good correlation as described by the following equation : Y = 5.03 X + 0.19 Where X is the pore size and Y is the mean particle size of the multiple prepared using membrane emulsifier technique

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FORMULATION OF MULTIPLE EMULSIONS: HLB OIL SURFACTANTS PHASE VOLUME NATURE OF ENTRAPED MATERIAL SHEAR/ AGITATION TEMPRATURE RHEOLOGY

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HLB: General procedure for the preparation of w/o/w multiple emulsion may involve the formation of primary emulsion of water in oil using lipophilic surfactant with a low HLB (2- 8) suitable for stabilization of such w/o system. Primary emulsion will then be emulsified in a second aqueous solution containing a second hydrophilic surfactant HLB (6- 16) to promote w/o emulsification.

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2.OIL: Nature of oil can affect the behavior of the system. Oils used to prepare multiple emulsions include liquid paraffin , vegetable oils like sesame oil, olive oil, isopropyl myristate e.t.c Selection of oil phase can affect various emulsion parameters like yield, release profile, particle size & emulsion stability. Release of drug from multiple emulsions is affected by the nature of oil phase due to difference in partition coefficient . . OIL

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3. SURFACTANTS: Selection of surfactant depends upon the use of multiple emulsions. Conc. Of surfactant also affects the emulsion yield. An excess of lipophilic surfactant can cause the inversion of w/o/w emulsion to simple o/w emulsion. For preparation of multiple emulsions two surfactants are necessary one for primary emulsion & other for dispersion of primary emulsion.

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4. PHASE VOLUME: It is very important to have proper order of phase addition while formulation is dispersed . Phase should be added slowly into the continuous phase for the formulation of a stable multiple emulsion . An optimal (22-50%) internal phase volume can be utilized for the emulsion formulation. Very high phase volume ratio (70- 90%) had also been reported to produce a stable multiple emulsion.

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5. NATURE OF THE ENTRAPED MATERIAL: It affects the stability of the system. Due to nature of multiple emulsion, middle phase act as membrane & osmotic effects may become significant. Entrapped solutions may interact with the surfactant or the surface active drugs may be adsorbed at the inter phase resulting in decreased stability .

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6. SHEAR / AGITATION: Increase shear disrupts the large percentage of multiple oil drops & hence results in the instability of the system due to tremendous increase in effective surface area Therefore with high homogenization time the yield of system falls rapidly . Generally high agitation speed is used for primary & low agitation speed is used for secondary emulsification for preparation of multiple emulsions.

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7. TEMPERATURE: It has only an indirect effect on emulsification that is attributed to its effects on viscosity, surfactant adsorption & interfacial tension . Generally for the primary emulsion formulation temp. is kept at 70 degree c where as for multiple emulsion preparation it is kept at 10 degree c Large temperature variations during manufacturing storage transport and use leads to drastic modification with in emulsion.

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8. RHEOLOGY : Rheological properties of emulsion are influenced by no. of factors including nature of continuous phase, the phase volume ratio, & to lesser extent by particle size distribution. For low internal phase volume emulsions the consistency of emulsion similar to the continuous phase thus o/w/o emulsions are generally thicker than w/o/w emulsions & the consistency of w/o/w system can be increased by the addition of gum clays.

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EVALUATION OF MULTIPLE EMULSIONS: CHARACTERIZATION AVERAGE GLOBULE SIZE & SIZE DISTRIBUTION NO. OF GLOBULES %age OF DRUG ENTRAPMENT RHEOLOGICAL EVALUATION ZETA POTENTIAL IN VITRO STABILITY STUDIES IN VITRO DRUG RELEASE

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CHARACTERIZATION: By size distribution of droplet & other physical properties such as dielectric properties , thermal behavior , rheological properties & other microscopic & macroscopic observation . MACROSCOPIC EXAMINATION: Primary observations like color , consistency & homogeneity are frequently used to ensure the formation of an emulsion . Type of multiple emulsions formed (w/o/w or o/w/o) can be validated by dilution with external phase .

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MICROSCOPIC EXAMINATION: Optical microscopy method stage micrometer can be used for globule size determination of both multiple emulsion droplets as well as droplets of simple emulsions. However this method has two draw backs Simple small drops passes to form large simple drop which gives a false impression of multiple nature. If the internal droplets are very small in size these can not be viewed due to reflection of light from the oil droplets surface.

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Various other techniques used to characterize emulsions like coulter counter , freeze fracture, electron microscopy& scanning electron microscopy are also used to determine average globule size & size distribution of multiple emulsion droplets .

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2. NO. OF GLOBULES: No. of globules per cubic mm can be measured by using a haemocytometer cell after appropriate dilution of multiple emulsions. Globules in 5 groups of 16 small squares ( total 80 small squares) can be counted & the total no. of globules per cubic mm is calculated by this formula :

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3. PERCENTAGE DRUG ENTRAPMENT: Determined by dialysis , centrifugation, filtration & conductivity measurement However recently an internal tracer/ marker was used to evaluate the entrapment of an impermeable marker molecule contained in the inner aqueous phase of w/o/w emulsion. Its formula is:

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4. RHEOLOGICAL EVALUATION: Rheology is an important parameter as it relates to emulsion stability & clinical performance Viscosity & interfacial elasticity are the two major parameters which relate to product R heology Viscosity of multiple emulsions can be measured by brook field rotational viscometer.

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5. ZETA POTENTIAL: Zeta potential & surface charge can be calculated using smoluchowski’s equation from the mobility & electrophoretic velocity of dispersed globules using the zeta potential . The apparatus consist of cylindrical bored micro –electrophoresis cell equiped with platinum irridium electrodes to measure the electrophoretic mobility of diluted w/o/w emulsion Equation here:

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6. IN VITRO STABILITY STUDIES: Phase separation is a phenomenon by which one phase of emulsion gets separated due to coalescence Percentage phase separation is the volume of phase in %age separated from the total volume of emulsion after storage . 20 ml of freshly prepared w/o/w emulsion is kept in 25 ml of graduated cylinder & allowed to stand for defined period at 40 degree c . The volume of separated aqueous phase (V sep) is observed periodically at regular intervals . Percentage phase separation is calculated using formula:

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7. IN VITRO DRUG RELEASE The drug released from the aqueous inner phase of w/o/w emulsion can be estimated using the conventional dialysis method using a cellophane tubing. Typically 5 ml of w/o/w multiple emulsion is placed in dialysis tube which is then tied at both ends by thread & placed in basket ( usually 100 rpm) & dialysed agent specified dissolution media ( usually 200ml ) at 37 +- 1 degree c Aliquots were withdrawn at different time intervals & replaced with fresh dissolution media & estimated drug standard procedure & the data was used to calculate cumulative drug release profile.

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STABILITY OF MULTIPLE EMULSIONS: Emulsion stability is a phenomenon, which depends upon the equilibrium between water, oil and surfactant. Multiple emulsions are thermodynamically unstable. The possible indications of instability include: Leakage of the contents from the inner aqueous phase. Expulsion of internal droplets in external phase. Constriction or distension of the internal droplets due to osmotic gradient across the oil membrane. Flocculation of internal aqueous phase and multiple emulsion droplets. Disruption of oil layer on the surface of internal droplets. Phase separation.

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Methods to Stabilize Multiple Emulsions : The followings are some of the attempt or studies made to restore or strengthen the stability of multiple emulsions : Liquid crystal stabilized multiple emulsion Stabilization in presence of electrolytes Stabilization by forming polymeric gel Stabilization by interfacial complexation between non-ionic surfactant and macromolecules Steric stabilization Phase-inversion stabilization of W/O/W emulsion

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Addition of antioxidant (sodium ascorbate & EDTA) to the o/w/o emulsion improve the stability of retinol upto 77.1% at 50 degree after 4 weeks . So it is concluded that the o/w/o emulsion is a useful formula to stabilize vitamin A.

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In theory, multiple emulsions have significant potential for breakthrough applications in food, agricultural, pharmaceutical, and cosmetic industries in which they can facilitate the sustained release and transport of active material. In cosmetics, these systems can prevent degradation of an active ingredient and release it at a controlled rate. They can also improve dissolutions or solubilization of insoluble materials. APLLICATONS OF MULTIPLE EMULSIONS

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Due to these properties, multiple emulsions find applications related to protecting sensitive and active molecules such as vitamins C and E from the external phase—a process called anti oxidation Water-in-oil-water (w/o/w) multiple emulsions and polymeric nanoparticle formulations containing influenza virus surface antigen haemagglutinin (HA) are thought to be suitable carriers for a vaccine delivery system.

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Vitamin c has been widely used in formulations of skin care products. Some important applications of multiple emulsions include 1).Controlled and sustained drug delivery 2).Drug targeting 3).Vaccine adjuvant 4).Enzyme immobilization 5).As a preparative tool for microencapsulation technology 6).Drug over dosage treatment/detoxification. 7).Protein action 8).Taste masking 9).Cosmetics and health care

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Bioavailability enhancer: Multiple Emulsions has also been used to improve bio-availability of lipophilic drugs which has high first pass metabolism. Multiple emulsion increase bioavailability of drugs either by protecting drugs in physiological, ionic/enzymatic environment in the GIT where otherwise these gets degraded like proteins, peptides or by- passing the hepatic first pass metabolism.

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TARGETED DRUG DELIVERY SYSTEM: Drug targeting minimizes the adverse effect of drugs by specifically concentrating drug in desired tissue several micro-particular interest for the cytotoxic drugs (anti-cancer agent).because of high toxicity for non-diseased tissue. Multiple emulsion system has also been prepared for several cytotoxic agents targeting different tumors these can be used as lymphotropic carriers for drug targeting.

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Target( Tissue/ organ) Drug investigated Lymphatic system 5-Fluorouracil ,Isoniazid Tumor Bleomycin Brain Rifampicin Liver 5-fluorouracil

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TASTE MASKING: Multiple emulsions has been employed for taste masking of drugs like chloroquine .it is an anti- malarial agent and has bitter taste Several bio compatible oils had been used for masking taste and improving the masking potential

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TREATMENT OF DRUG OVERDOSE: Multiple emulsion of w/o/w types are used for the treatment of drug overdosing A w/o/w system was designed to remove acidic drugs like barbiturates and salicylates from the gastro intestinal tract by entrapping unionized drug, permeating through the oil membrane into inner basic phase, where it is converted to an oil insoluble anion .

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COSMETIC AND HEALTH CARE: Multiple emulsions are used for moisturizing nutritive and protective action, when applied in the form of sunscreens hand creams, makeup cleanser, perfume preparations In o/w/o emulsion consisted of a primary oil-in –water phase consisting of a viscoplastic gel containing at least one organic UV absorbent in the oil droplets , while the secondary oil phase ( silicone oil ) containing one or more UV absorbents.

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Controlled and sustained Drug delivery: The basic potential of multiple emulsions (both W/O/W and O/W/O) in clinical therapeutics is in the prolonged and controlled release of drug. In both systems drug present in inner most phase has to cross several phases before it is available for absorption for system. The w/o/w emulsions for parenteral delivery are more convenient due to lower viscosity of these systems.

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COSMETIC AND HEALTH CARE: Multiple emulsions are used for moisturizing nutritive and protective action, when applied in the form of sunscreens hand creams, makeup cleanser, perfume preparations

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Various pharmaceutical applications include immobilization of enzymes , red blood cell substitutes, transdermal delivery , bioavailability enhancement, taste masking, drug targeting, prolong delivery of drugs e.t.c .

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Marketed Multiple Emulsions Sandostatin LAR TM Depot – Novartis (hypothalamic hormones analogue) Control of hyper secretion at the site of the tumour where hormone overproduction starts IVY FORMULA 30 Main Treatment Multiple Emulsion- IVY FORMULA 30 was created as a futuristic skin care treatment that is concentrated into four short weeks. A 4-week concentrated treatment that restores the keratinization cycle and awakens and boosts the skin’s “underlying strength.”-marketed by IVY Cosmetics

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Micro-emulsions meter < 100 nm ) of water in oil or oil in water, depending on the nature of the surfactant. Micro-emulsions are thermodynamically stable , optically transparent , isotropic dispersions of aqueous and hydrocarbon liquids stabilized by an interfacial film of surfactant molecules Micro-emulsions are mono-dispersed spherical droplets ( diameter < 100 nm ) of water in oil or oil in water, depending on the nature of the surfactant.

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Micro-emulsion Macro emulsion Thermodynamically Stable Kinetically Stable Droplet size 10 - 100 nm (transparent) 1-10 m (opaque) High surface area: 200 m 2 /g Low surface area: 15 m 2 /g W/O , O/W and Bi-continuous types W/O or O/W types Difference between Micro-emulsions and (Macro) emulsions

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REFRENCES http ://www.authorstream.com/Presentation/bhavanibhaskar04-873291-multiple-emulsions / Pharmaceutical Emulsions and Suspensions, edited by Francoise Nielloud Gilberte Marti- Mestres . Pharmaceutical Dosage Forms: Disperse systems, vol.3, second edition, Edited by Herbert A.Liberman , Martin M. Rieger and Gilbert S. Banker. some studies on Multiple Emulsions by G.Vishwanadham , ( Ph.D thesis, KU) http://www.aapsj.org/view.asp http://www.blackwell-synergy.com http://www.rsc.org/delivery/_ArticleLinking http://cat.inist.fr http://iufost.edpsciences.org

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