22-11-2012, 11:40 AM
NANOPARTICLES
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INTRODUCTION
New drug delivery systems provide excellent drug carriers for optimal drug activity.
It is necessary to deliver the drug to the body and its site of action as efficiently as possible and more effectively.
Thus it is possible reduce the total dose of drug which must be administered to achieve a therapeutic response and minimize any unwanted toxic effects.
Such systems include microcapsules, macromolecular complexes, polymeric beads microspheres, liposomes, nanocapsules.
DEFINITION:
Nanoparticles are sub-nanosized colloidal drug delivery systems and the particle size ranges from 10-1000 nm in diameter.
They are composed of synthetic or semi synthetic polymers. The polymeric nanoparticle can carry drugs or proteinaceous substances, i.e. antigens.
They are entrapped in the polymer matrix as particulates or may be bound to the particle surface by physical adsorption or chemically.
The drugs may be added during preparation of nanoparticles or to the previously prepared nanoparticles.
TYPES OF NANOPARTICLES:
Nanospheres:may be defined as solid core spherical particulates, which are nanometric in size. They contain drug embedded within the matrix or adsorbed onto the surface.
Nanocapsules:are vesicular systems in which drug is essentially encapsulated within the central volume surrounded by an embryonic continuous polymeric sheath.
Nanocrystals or nanoparticulates: here the drug is encapsulated in the solution system.
AMPHIPHILIC MACROMOLECULE CROSS-LINKING
Nanoparticles can be prepared from amphiphilic macromolecules, proteins and polysaccharides.
The method involves Aggregation of amphiphiles followed by stabilization either by heat denaturation or chemical cross-linking.
Types:
Cross-linking in W/O emulsion
Emulsion chemical dehydration
Phase separation in aqueous medium (Desolvation)
POLYMERIZATION BASED METHODS
Two different mechanisms were proposed for the emulsion polymerization process based on the site of polymerization.
Micellar nucleation and polymerization.
Homogenous nucleation and polymerization.
Dispersion polymerization
Interfacial condensation polymerization
Interfacial complexation
APPLICATION OF NANOPARTICLES
Cancer therapy
Intracellular targeting
Prolonged systemic circulation
Vaccine adjuvant
Ocular delivery and DNA delivery
Oligo nucleotide delivery
Lymph targeting