1. Colloid An Introduction
Physical Pharmacy 2
4/16/2017
Colloid An Introduction
Kausar Ahmad
Kulliyyah of Pharmacy
Physical Pharmacy 2
KBA

2. Lecture 1: Lecture 2: Contents Types of colloids Types of dispersions
Physical Pharmacy 2
4/16/2017
Contents
Lecture 1:
Types of colloids
Types of dispersions
Lecture 2:
Types of emulsions
Emulsification factors
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3. Colloidal System Discrete particles dispersed in a different medium
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Colloidal System
Particle size below 1 mm
High specific surface area
Discrete particles dispersed in a different medium
In pharmaceutical emulsions or suspensions, particle size ranges from colloidal to visible or coarse.
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4. Multiple emulsion: w/o/w, o/w/o
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Types of Colloids
Type
Dispersed
phase
Continuous phase
Emulsion: o/w
oil
water
Emulsion: w/o
Suspension
solid
water or oil
Aerosol
solid or liquid
air
Others
Multiple emulsion: w/o/w, o/w/o
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5. Classification Based on Size
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Classification Based on Size
Class
Size
Examples
Molecular dispersion
< 1.0 nm
glucose
Colloidal dispersion
1.0 nm mm
Natural rubber latex
Coarse dispersion
> 0.5 mm
red blood cells
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6. Classification of dispersed systems
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Classification of dispersed systems
hydrophilic colloidal dispersion (in water)
surfactant micelles and phospholipid vesicles, also known as association colloids
lyophilic colloids
proteins, gelatin
rubber, gum
lyophobic/hydrophobic colloids
gold, silver and sulfur
emulsion
Sol – refers to any colloidal system in which the dispersion medium is a liquid.
Lyophilic sol – a sol consisting of a dispersed phase which has an affinity for the continuous phase.
This means that the colloid is readily formed e.g. starch in water.
Lyophobic sol – a sol which is solvent-repelling, such that the disperse phase has little or no attraction for the dispersion medium
e.g. gold in water.
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7. Colloidal Phenomena milk detergency coconut milk ice-cream
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Colloidal Phenomena
detergency
milk
coconut milk
ice-cream
Detergency
Most important products using surfactants
Main component is surfactant
Involves in adsorption, wetting, emulsification and dispersion
Wetting of substrate ->soil-removing process ->preventing soil redeposition (PEG)
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8. Pharmaceutical suspensions
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Pharmaceutical suspensions
Coarse dispersions
Solid-in-liquid
Main function
Delivery vehicle for suspended drug particles
Surfactant/dispersant reduces interfacial energy
Stabilisation by electric repulsive force & steric hindrance effect
Examples: Oral suspensions, topical applications, injectables
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9. Preparing a Dispersion
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Preparing a Dispersion
Particle size reduction
surface of each primary particle is available to liquid.
Wetting of powder
wet external surfaces & displace air between internal clusters.
Dispersing by using charged bulky surfactants
Provide strong interfacial layer
Modifying the viscosity
to minimise sedimentation
Dry powders usually consist of aggregates and agglomerates which need to be dispersed in the liquid to produce "individual" units which may be further subdivided into smaller particles.
This requires understanding of various phenomena such as powder wetting, dispersion of aggregates and agglomerates and comminution of the primary particles into smaller units. HOW?
Once a powder is dispersed into a liquid, it is essential to prevent aggregation of the particles and their sedimentation.
Powder wetting, dispersion and subsequent stabilization requires in most cases the use of a dispersing agent, usually a surfactant, a polymer or polyelectrolyte.
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10. Properties of dispersing agents
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Properties of dispersing agents
adsorption of surfactants at the solid/liquid interface.
highly charged
provide steric hindrance
END OF LECTURE 1 OF 2
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11. Pharmaceutical Emulsions
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Pharmaceutical Emulsions
Emulsion
liquid-in-liquid vehicle
o/w or w/o
Main function
provide vehicles for drug delivery and parenteral nutrition.
drug is dissolved in the water or oil phase.
Surfactant/emulsifier reduces interfacial energy
emulsion becomes thermodynamically stable
Examples:
parenterals, creams, lotions
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12. Emulsification emulsifier homogeniser OIL WATER Physical Pharmacy 2
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Emulsification
emulsifier
homogeniser
OIL
WATER
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13. Emulsification Factors
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Emulsification Factors
Concentration of dispersed/oil phase
Types & concentrations of surfactants
Emulsifying temperature especially for non-ionic surfactants
Type of homogeniser
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14. Types of Emulsions Macroemulsion Nanoemulsion Microemulsion
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Types of Emulsions
Macroemulsion
Nanoemulsion
Microemulsion
Multiple emulsion
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15. Nanoemulsion and Microemulsion
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Nanoemulsion and Microemulsion
Nanoemulsions: nm
Microemulsions: 5-50 nm
long term physical stability against creaming, flocculation and coalescence
Due to small size they enhance penetration, spreading and will give uniform distribution on the substrate on which they are applied.
Examples: personal care products and cosmetics, agrochemicals, pharmaceuticals, household products etc.
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16. Methods of Preparation
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Methods of Preparation
Nanoemulsions are easily formulated using high-pressure homogenizers with proper choice of surfactants and/or polymers.
The production of microemulsions may employ the Phase Inversion Temperature (PIT) principle.
These emulsions are stabilised through steric stabilization and by the thickness of the adsorbed layer.
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17. Multiple Emulsion Dispersed phase contains droplets of another phase.
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Multiple Emulsion
Dispersed phase contains droplets of another phase.
o/w/o or w/o/w.
Prepared through a double homogenization process or a one step procedure using the PIT.
Both are important for drug delivery.
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18. Example of w/o/w emulsion for drug delivery by intra-muscular route
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Example of w/o/w emulsion for drug delivery by intra-muscular route
Advantage of w/o:
slow-release because drug has to diffuse through oil
disadvantage: viscosity of medium (oil) is high
solution: to disperse the w/o in aqueous medium.
On injection, the aqueous phase dissipates rapidly leaving behind the w/o.
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19. Multiple Emulsion for Pharmaceuticals Examples
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Multiple Emulsion for Pharmaceuticals Examples
Sandostatin LARTM Depot
Novartis (hypothalamic hormones analogue)
Control of hypersecretion at the site of the tumour where hormone overproduction starts
Human NutropinTM Depot
Alkermes/Genentech (human insulin suspension)
somatropin (rDNA origin) for injectable suspension
long-acting dosage form of recombinant human growth hormone (rhGH).
11/6/2003
J Wang et al, Journal of Controlled Release 82 (2002)
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20. Multiple emulsion Pharmaceutical Problems
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Multiple emulsion Pharmaceutical Problems
typically accounts for 10-80% of the total drug loading.
This ‘initial burst’ poses a toxicity threat & is a major hurdle for the development of microspheres.
Rapid release during the first day
This can last for weeks and is referred to as the ’lag-time’.
During this induction period, the patient is not effectively treated due to lack of drug release.
Very slow release period after the initial burst period.
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21. Physical Pharmacy 2
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References
PC Hiemenz & Raj Rajagopalan, Principles of Colloid and Surface Chemistry, Marcel Dekker, New York (1997)
HA Lieberman, MM Rieger & GS Banker, Pharmaceutical Dosage Forms: Disperse Systems Volume 1, Marcel Dekker, New York (1996)
F Nielloud & G Marti-Mestres, Pharmaceutical Emulsions and Suspensions, Marcel Dekker, New York (2000)
J Kreuter (ed.), Colloidal Drug Delivery Systems, Marcel Dekker, New York (1994)
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