Stability of Niosomes
The factors affecting the stability of niosomes can be classified into
the three categories-
• Physical stability
• Chemical stability
• Stability in biological fluids.
Physical stability
The niosomes can change their physical characteristics in several
ways.
a. The particle size may change because of aggregate formation
and fusion.
a. Occurrence of phase separation of bilayer components, upon
storage.
b. Leakage of encapsulated material from niosomes.
The changes in particle upon storage of phosphatidyl choline
containing niosomes over pharmaceutically relevant time intervals
can be minimized by the selection of proper charge inducing agents.
Mostly, negatively charged phospholipids (phosphatidyl glycerol)
are used to stabilize the niosomes.
The phase separation may occur when the bilayer composition
changes due to chemical degradation reactions or when the bilayer
goes through temperature cycles (Lichtenberg and Bahrenholz,
1988). Sometimes, phase separation occurs in vivo, when bilayer
components are selectively drawn from the bilayer plasma
components (Scherphof, 1984). If this effect is undesired, the
components that form more rigid bilayers are preferred. In other
cases, one might wish to deliberately destabilize the niosomes in
vivo so that a rapid release of the encapsulated drug is induced. An
example of plasma destabilized niosomes is niosomes composed of
phosphatidyl ethanolamine and oleic acid (New, 1990).
Stability of Niosomes
The factors affecting the stability of niosomes can be classified into
the three categories-
• Physical stability
• Chemical stability
• Stability in biological fluids.
Physical stability
The niosomes can change their physical characteristics in several
ways.
a. The particle size may change because of aggregate formation
and fusion.
a. Occurrence of phase separation of bilayer components, upon
storage.
b. Leakage of encapsulated material from niosomes.
The changes in particle upon storage of phosphatidyl choline
containing niosomes over pharmaceutically relevant time intervals
can be minimized by the selection of proper charge inducing agents.
Mostly, negatively charged phospholipids (phosphatidyl glycerol)
are used to stabilize the niosomes.
The phase separation may occur when the bilayer composition
changes due to chemical degradation reactions or when the bilayer
goes through temperature cycles (Lichtenberg and Bahrenholz,
1988). Sometimes, phase separation occurs in vivo, when bilayer
components are selectively drawn from the bilayer plasma
components (Scherphof, 1984). If this effect is undesired, the
components that form more rigid bilayers are preferred. In other
cases, one might wish to deliberately destabilize the niosomes in
vivo so that a rapid release of the encapsulated drug is induced. An
example of plasma destabilized niosomes is niosomes composed of
phosphatidyl ethanolamine and oleic acid (New, 1990).
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