Emulsions, Microemulsions, and Nanoemulsions

Done By: Hussein Talal & Sarmad Usama

ID NO.201117011 & 201127022

Supervised by: Dr. Israa’ Al-Ani

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Microemulsions

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Micro emulsions

• Modern colloidal drug delivery system

• Micro emulsions are clear, transparent, thermodynamically stable dispersions of oil and water, stabilized by an interfacial film of surfactant frequently in combination with a co-surfactant.

• Diameter - 5 nm-200 nm

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Alternative names for Micro emulsions

• Transparent emulsion

• Swollen micelle

• Micellar solution

• Solubilized oil

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Goal of micro emulsions

• To deliver hydrophilic as well as lipophilic drug as drug carriers because of its

1. improved drug solubilization capacity,

2. long shelf life,

3. easy of preparation and

4. improvement of bioavailability.

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Micro emulsions vs. Macr oemulsions

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Micro emultions vs. Macro emultions

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FEATURES MACRO EMULSION MICRO EMULSION

DEFINITION Emulsions consist of roughly spherical droplets of one phase dispersed into the other

They constantly evolve between various structures ranging from droplet like swollen micelles to bi continuous structure.

DROPLET SIZE

1 – 20 mm. 10 – 100 nm.

APPEARANCE

Most emulsions are opaque (white) because bulk of their droplets is greater than wavelength of light and most oils have higher refractive indices than water.

Microemulsions are transparent or translucent

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FEATURES MACRO EMULSION MICRO EMULSION

PHASES Two One

STABILITY Stable but coalesce finally More thermodynamically stable than macroemulsions

PREPARATION Require intense agitation for their formation.

Generally obtained by gentle mixing of ingredients.

SURFACTANT CONCENTRATION

2-3 % Weight 6-8% by weight

Micro emulsions vs. Macro emulsions

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Advantages of micro emulsions

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1. These are thermodynamically stable and require minimum energy for formation.

2. Ease of manufacturing and scale-up

3. Improved drug solubilization and bioavailability.

4. This system is reckoned advantageous because of its wide applications in colloidal drug delivery systems for the purpose of drug targeting and controlled release

5. The formation of micro emulsion is reversible.  They may become unstable at low or high temperature but when the temperature returns to the stability range, the micro emulsion reforms.

6. The use of microemulsion as delivery systems can improve the efficacy of a drug, allowing the total dose to be reduced and thus minimizing side effects.

Formation of micro emulsion

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• Micro emulsion is formed

when:

1. the interfacial tension at the O/W interphase are brought very low level.

2. The interfacial tension is kept highly flexible and fluid.

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Applications of micro emulsions

1. Oral drug delivery: e.g. Atorvastatin

2. Ocular drug delivery

3. Pulmonary drug delivery

4. Transdermal drug delivery

5. Parenteral drug delivery

6. For solubilization of drug

7. In biotechnlogy

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Applications of micro emulsions

Topical drug delivery

• Microemulsions may enhance transdermal drug delivery primarily by the following effects:

1. Micro emulsions can exhibit a high solubilization capacity for both lipophilic and hydrophilic drugs, thus more drug can be loaded into the microemulsion, which increases the concentration gradient across the skin without depletion.

2. The reservoir effect of the internal phase maintains a constant driving force of drug from the external phase to the skin and prolongs absorption.

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Applications of micro emulsions

Topical drug delivery

3. The formulation components may affect skin permeability, i.e. surfactants, cosurfactants, and oils may act as permeation enhancers by increasing the partition of the drug in the skin.

4. Chemical enhancers may be incorporated in the microemulsion, which will also improve dermal and transdermal delivery of drugs.

5. The very low interfacial tension required for microemulsion formation is also responsible for the excellent wetting properties, which ensures excellent surface contact between the membrane and the vehicle.

6. There is no clear consensus in the literature regarding the influence of droplet size of the microemulsion on drug permeation.

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Nanoemulsions

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Nanoemulsion

• The term "Nanoemulsion" refers to a thermodynamically stable isotropically clear dispersion of two immiscible liquids, such as oil and water, stabilized by an interfacial film of surfactant molecules.

• The dispersed phase typically comprises small particles or droplets, with a size range of 5 nm-200 nm, and has very low oil/water interfacial tension. Because the droplet size is less than 25% of the wavelength of visible light, Nanoemulsions are transparent.

• The Nanoemulsion is formed readily and sometimes spontaneously, generally without high-energy input.

• In many cases a cosurfactant or cosolvent is used in addition to the surfactant, the oil phase and the water phase.

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Types of Nanoemulsion

Three types of Nanoemulsions are most likely to be formed depending on the composition:

 

• Oil in water Nanoemulsions wherein oil droplets are dispersed in the continuous aqueous phase

 

• Water in oil Nanoemulsions wherein water droplets are dispersed in the continuous oil phase;

• Bi-continuous Nanoemulsions wherein microdomains of oil and water are interdispersed within the system.

 

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Difference between emulsions and Nanoemultion

The key difference between emulsions and Nanoemulsions are:

• That the former, whilst they may exhibit excellent kinetic stability, are fundamentally thermodynamically unstable and will eventually phase separate.

• Another important difference concerns their appearance; emulsions are cloudy while Nanoemulsions are clear or translucent.

• In addition, there are distinct differences in their method of preparation, since emulsions require a large input of energy while Nanoemulsions do not.

• The latter point has obvious implications when considering the relative cost of commercial production of the two types of system.

 

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Advantages of Nanoemulsions over other dosage forms

1. Increase the rate of absorption.

2. Eliminates variability in absorption.

3. Helps solublize lipophilic drug.

4. Provides aqueous dosage form for water insoluble drugs.  

5. Increases bioavailability.  

6. Various routes like tropical, oral and intravenous can be used to deliver the product.

7. Rapid and efficient penetration of the drug moiety.

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Advantages of Nanoemulsions over other dosage forms

8. Less amount of energy requirement.

9. Nanoemulsions are thermodynamically stable system and the stability allows self-emulsification of the system

10. Helpful in taste masking.

11.  Provides protection from hydrolysis and oxidation as drug in oil phase in O/W Nanoemulsion is not exposed to attack by water and air.

12. Liquid dosage form increases patient compliance.

13.  Less amount of energy requirement.

14. Same Nanoemulsions can carry both lipophilic and hydrophilic drugs.

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Disadvantages of Nanoemulsions over other dosage forms

• Use of a large concentration of surfactant and co-surfactant necessary for stabilizing the nanodroplets.

• Limited solubilizing capacity for high-melting substances. 

• The surfactant must be nontoxic for using pharmaceutical applications.

 

• Nanoemulsion stability is influenced by environmental parameters such as temperature and pH.

• These parameters change upon Nanoemulsion delivery to patients.

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Preparation of Nanoemulsions

• The drug is be dissolved in the lipophilic part of the Nanoemulsion i.e. oil and the water phases can be combined with surfactant and a cosurfactant is then added at slow rate with gradual stirring until the system is transparent.

• The amount of surfactant and cosurfactant to be added and the percent of oil phase that can be incorporated shall be determined with the help of pseudo-ternary phase diagram.

• Ultrasonicator can finally be used so to achieve the desired size range for dispersed globules.

• It is then being allowed to equilibrate. Gel may be prepared by adding a gelling agent to the above Nanoemulsion.

• Carbomers (crosslinked polyacrylic acid polymers) are the most widely used gelling agent.

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Factors to be considered during preparation of Nanoemulsions

Three important conditions:

 

• Surfactants must be carefully chosen so that an ultra low interfacial tension (< 10-3 mN/m) can be attained at the oil / water interface which is a prime requirement to produce Nanoemulsions.

• Concentration of surfactant must be high enough to provide the number of surfactant molecules needed to stabilize the microdroplets to be produced by an ultra low interfacial tension.

 

• The interface must be flexible or fluid enough to promote the formation of Nanoemulsions.

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Applications of Nanoemulsion

1. Parenteral delivery

2. Oral drug delivery

3. Topical drug delivery

4.  Ocular and pulmonary delivery

5. Nanoemulsions in biotechnology

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Stability studies

• The physical stability of the Nanoemulsion must be determined under different storage conditions (4, 25 and 40 °C) during 12 months.

• Fresh preparations as well as those that have been kept under various stress conditions for extended period of time are subjected to droplet size distribution analysis.

• Effect of surfactant and their concentration on size of droplet is also being studied.

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Nanoemulsions

Conclusion :

• Conclusion Nanoemulsion formulations offer several advantages for the delivery of drugs, biological or diagnostic agents.

• Nanoemulsions can be formulated in a variety of formulations such as foams, creams, liquids and sprays.

• Recently, nanoemulsions have been used in several drug delivery applications such as targeted drug delivery, mucosal vaccines, In cell culture technology, anti-cancer, anti-HIV therapy and diagnostic agents.

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Thank you

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References1-http://www.ncbi.nlm.nih.gov/pubmed/19958051

2- PHARMACIE GLOBALE

 INTERNATIONAL JOURNAL OF COMPREHENSIVE PHARMACY

NANOEMULSIONS: AS MODIFIED DRUG DELIVERY TOOL

Department of pharmacy, Vels University, Velan Nagar, Pallavaram, Chennai, Tamilnadu, India. Received: 28 December 2010; Revised: 12 January

2011; Accepted: 28 March 2011; Available online: 5 April 2011

online at www.pharmacie-globale.info

3-http://www.slideworld.org/viewslides.aspx/Microemulsions-ppt-220667

4-http://www.authorstream.com/Presentation/aSGuest54570-439278-microemulsion/

5-http://www.firp.ula.ve/archivos/cuadernos/00_Book_Salager_Chap3.pdf

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