27-11-2012, 04:59 PM
Micelle
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what is micelle?
Micelle is an aggregate of amphipathic molecules in water, with the nonpolar portions in the interior and the polar portions at the exterior surface, exposed to water
It differ from lipid bilayer by having single hydrophilic heads
Micelle exibhit anisotrophic distribution in water within structure – water concentration decreases from the surface towards the core.
Normal phase miscille – forms by exposing hydrophilic head outside with hydrophobic tails inside as core. ( oil in water)
Reverse phase miscille- forms by exposing hydrophobic tail outside with hydrophilic heads inside ( water in oil)
How are micelles formed?
Micelles are formed when the surfectant concentration exceeds critical micellar concentration (CMC).
Temperature of the system should also be greater than CMC temperature.
Due to the balance between entropy and enthalpy, micelles are formed spontaneously.
Factors affecting size of micelles and CMC
It is clear that micelle formation depend upon critical micellar concentration (CMC)
Effect of hydrophobic group: If the hydrophobic group is aromatic, then micelles does not formed.
Length of the hydrocarbon chain is directly proportional to the size of the micelles and inversely proportional to the CMC.
SHAPE & STRUCTURE OF MICELLES
Micelles exibhit following shapes
Spherical
Prolate
Oblate
Disk
Invered
Variation in shapes mainly depends upon the type of surfectants used.
Structure of micelles are of ionic micelles and non ionic micelles.
Micelles in pharmaceutical biotechnology
Micelles are having crucial applications in pharmaceutical biotechnology.
Due to the presence of hydrophobic core, hydrophobic drugs can be solubilized with the core of micelles and used for delivery.
The spatial position of the solubilized drug in in micelles depends upon the polarity of the drug.
Polymeric micelle is used to target the tumor site by passive as well as active mechanism
Micelle is used in ophthalmic drug delivery system, that effectively delivers the drug to posterior tissue of eyeball
Micelle is used to encapsulate the antibiotic & anticancer drugs.