concept of micelle & cmc
TRANSCRIPT
Presented by
Akshay A. Pawar
M. Pharm 1st Sem
Department of Pharmaceutics
R. C. Patel Institute of Pharmaceutical Education & Research, Shirpur
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CONTENT
Introduction
Surfactant
Concept of Micelle
Micelle formation
Critical micelle concentration (CMC)
Determination of the CMC
Factors affecting CMC
Micelle Solubilization
Conclusion
Introduction
In dilute solution Amphiphiles tend to reduce Surface
tension
As concentration molecules of amphiphiles goes on
increasing they disturb hydrogen structure, to
minimize the disturbance molecules tend to form
aggregate into a structure
Structure called as micelle and Amphiphilic molecule
Surface Active Agent 3
Surfactant• A micelle is an aggregates of Surfactant molecules
dispersed in liquid collide
• Surfactants (amphiphilic
molecules) composed of a
hydrophilic moiety known
as head and a hydrophobic
moiety known as tail.4
PHYSICOCHEMICAL BACKGROUND
cohesive forces between molecules down into liquid
the intermolecular attractive forces is called surface
tension5
• A micelle is an aggregate of monomer surfactant
molecules dispersed in a liquid colloid.
• Hydrophilic "head" regions in contact with
surrounding solvent, sequestering the hydrophobic tail
regions in the micelle centre. (oil-in-water micelle).
• Inverse micelles have the head groups at the centre with
the tails extending out (water-in-oil micelle).
Micelle
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Micelle formation•The process of forming micelle is known as
micellization.
•Typical micelle is Spherical in structure which contain
50-100 monomers
•Number of monomers to form micelle is called as
aggregation number
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SAA bulk Concentration
Surface excess
Surface saturated with SAA
Excess in the bulk
Micelles( colloidal aggregates)
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Oil in Water TypeBecause of arrangement monomers micelle is capable to hold lipidicnature drug at centre
Water in oil typeIn Reversed micelle at middle able to hold relatively large amounts of water in their interior. In that way, a "pocket" is formed which is particularly suited for the dissolution and transportation of polar solutes through a non polar solvent. 9
Critical micelle concentration (CMC)
The lowest concentration at which micelles first
appear is called the critical concentration for micelle
formation
The critical micelle concentration is the point at
which surfactant molecules aggregate together in
the liquid to form groups known as micelles.
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The critical micelle concentration of a surfactant
indicates the point at which surface active properties
are at an optimum and performance is maximised.
The CMC is the concentration above surfactant when
micelles will form spontaneously.
Increase in concentration of surfactant beyond CMC
change number size or shape but not provide increase
in concentration of monomeric species 11
Micelles are formed at the critical micelle
concentration (CMC), which is detected as an
inflection point in physical properties which are
plotted as a function of concentration.
• surface tension,
• Conductivity,
• Turbidity,
• Osmotic Pressure
Determination of the CMC
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1. At very low concentrations of surfactant only slight change in surface tension is detected.
2. Additional surfactant decreases surface tension
3.Surface becomes fully loaded, no further change in surface tension.
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Factors Affecting CMC
Structure of hydrophobic group. –
length of hydrocarbon chain is
Micelle size CMC
Addition of Electrolyte
Micelle Size CMC
Effect of Temperature
up to cloud point
Micelle Size CMC
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Thermodynamic aspect
The formation of micelle can be understood using
thermodynamics: micelles can form spontaneously
because of balance between entropy and enthalpy
For ionic surfactants, the solubility of a material will
often be observed to undergo a sharp, discontinuous
increase at some characteristic temperature,
commonly referred to as the Krafft temperature, Tk.
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A surfactant, when present at low concentrations in a
system, adsorbs onto surfaces or interfaces
significantly changing the surface or interfacial free
energy
Primary reason of micelle formation is attainment of
minimal free energy
Free energy change ∆G depend upon both Etropy,S
and Enthlpy H at temperature T
∆G= ∆H-T∆S (T∆S is 90-95% value of ∆G)17
SolubilizationMicelle can be used to increase the solubility of
material that are normally insoluble or poorly soluble
in dispersed medium phenomenon called as
solubilization
Importance
Hydrophilic drugs can be adsorbed on the surface of
the micelle.
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Drugs with intermediate Solubility should be located
in intermediate positions within the micelle such as
between the hydrophilic head group of Peo Micelles
In the Palisade Layer between the hydrophilic group
and the first few carbon atoms of the hydrophobic
group , that is the outer core.
Completely insoluble hydrophobic drugs may be
located in the Inner Core of the micelle.
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Conclusion
By using Phenomenon of micellization we improve
solubility of API
Considering factor of CMC we modify micelle size
Shape & release profile
Applying this knowledge in field of Pharmacy
Improve API stability
Maintain Bioavailability long period
Research is continue in Targeted DDS (Cancer)20
References
A. N. Martin, Martin's Physical Pharmacy and Pharmaceutical Sciences, 6th edition, p.
M.E. Aulton, Pharmaceutics science of dosage form design, 2nd Edition, p. 88-89
Leon Lachman, The Theory and Practice of Industrial Pharmacy, 3rd edition, p. 106
H.A. Liebereman, M.M. Rieger, G.S. Banker, Pharmaceutical Dosage Forms: Disperse Systems,2nd Edition, Vol.3, p. 216-220
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Sanjay K. Jain, Vandana Soni, Benley’s Text Book of Pharmaceutics, p.68-74
Ram I. Mahato Pharmaceutical Dosage Forms and Drug Delivery,CRC press pharmacy education series, p.111-119
Nita K. Pandit & Robert R. Soltis, Introduction to the Pharmacetical Sciences 2nd Edition, p.54-55
Online Reference
http://www.biolinscientific.com/attension/applications/?card=AA8
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