Nanoparticles are sub-nano-sized
colloidal structures composed of synthetic or semi-synthetic polymers.
Its size ranges from 1-100nm.
One can distinguish two types of nanoparticles
1.Nanospheres
2.Nanocapsule1.Nanospheres
Nanospheres - matrix systems.
Nanocapsules - which are reservoir
systems composed of a polymer membrane surrounding an oily or aqueous core.
Advantages of Nanoparticles:
Ā·
More
uniform effect of the drug
Ā·
Reduction
in the frequency of the dosages
Ā·
Site
specific targeting
Ā·
Various
routes of administration
Ā·
Better
drug utilization and less side effects
Disadvantages
of Nanoparticles:
⢠High cost
⢠Productivity more difficult
⢠Reduced ability to adjust the dose
⢠Highly sophisticated technology
⢠Requires skills to manufacture
⢠Difficult to maintain stability of
dosage form.
Polymers
used in preparation of nanoparticles:
NATURAL
HYDROPHILIC
Eg:
proteins
Polysaccharides
SYNTHETIC
HYDROPHOBIC
Eg:
polyesters
Polystyrene
Methods of preparation
A: Amphiphilic
Macromolecules Cross Linking
1) Heat
crosslinking.
2) Chemical
crosslinking.
B:
Polymerization Methods
1) Emulsion
polymerization
2)
Dispersion polymerization
3)
Interfacial condensation polymerization
4)
Interfacial complexation
C : Polymer
precipitation methods
1) Solvent
evaporation method
2) Solvent
displacement
3) Salting
out
A :
Molecular crosslinking in emulsion
B :
Polymerization Methods:
Emulsion polymerization :
It consists of
a) Micellar nucleation and polymerization :
Monomer is insoluble in continuous phase.(O/W phase)
Aqueous phase
b)Homogenous nucleation and polymerization :
Monomer is soluble in continuous phase.(W/O phase)
Organic phase.
Dispersion
polymerization:
Interfacial
polymer condensation:
C :
Polymer Precipitation Methods:
The polymer
precipitation occurs as a consequence of solvent evaporation which can be
brought about by increasing solubility of organic solvent in external medium by
adding alcohol (Eg. Isopropanolol)
They are 3 types
- Solvent evaporation method
- Solvent displacement
- Salting out
1.
Solvent
Evaporation Method
2.
Solvent
Displacement Method
3. Salting out of Polymer:
Evaluation of nanoparticles
1.
Paricle size :
Ā·
Photon
correlation spectroscopy(PCS) : For smaller particle.
Ā·
Laser
diffractometric : For larger particle.
Ā·
Electron
microscopy (EM) : Required coating of conductive material such as gold &
limited to dry sample.
Ā·
Transmission
electron microscopy (TEM) : Easier method & Permits differntiation among
nanocapsule & nanoparticle .
Ā·
Atomic
force microscope
Ā·
Laser
force microscope
Ā·
Scanning
electron microscope
2.Density :
Helium or air using a gas pycnometer
Density gradiant centrifugation
3. Molecular
weight :
Gel permeation chromatography using
refractive index detector.
4. Structure & Crystallinity :
X-ray diffraction Thermoanalytical method
such as,
1) Differential scanning calorimetry
2) Differential thermal analysis
3) Thermogravimetry
5. Surface charge:
Surface charge of particle can be
determined by measuring particle velocity in electrical field.
6. Invitro release
:
Diffusion cell
Recently introduced modified
Ultra-filtration tech.
Media used : phosphate buffer
7.
Nanoparticle yield
% yield= (Actual weight of product)
______________________ X 100
(Total
weight of excipient and Drug)
Comments
Post a Comment