Production Techniques - Lipid Nanoparticles: Production, Characterization and Stability - page 29

Lipid phase
(Lipid + Drug)

Solid lipid-drug
mixture

Lipid
Microparticles

Solid lipid microparticle
dispersion

Step 1: Heating
lipid phase

Step 2: Rapid
cooling

Step 3: Milling into a
fine powder

Step 4: Dispersion of
fine powder Step 5: Homogenization

Solid lipid
nanoparticles

Fig. 3.2 Schematic steps involved in the cold homogenization technique

energy input which in turn requires harsh homogenization conditions. Thus
homogenisation itself is more effective for the hot case, and smaller particles
which are more monodisperse result (Mäder and Mehnert 2005 ).

3.2.2 Microemulsion Technique

The preparation of SLN dispersions by precipitation from a hot microemulsion
was described by Gasco ( 1993 ). A microemulsion is a thermodynamically stable
system comprising of water and oil, stabilized by surfactant (and a co-surfactant, if
required) and is optically isotropic.
Figure 3.3 depicts the preparation of lipid nanoparticle dispersion by pre-
cipitation from a hot microemulsion. The lipid phase and aqueous surfactant/

Lipid phase
(Lipid + Drug)

Solid lipid
nanoparticles

Hot microemulsion

Aq. phase

Step 2: Dispersing lipid
melt in aq. phase

Step 3: Dispersion in
cold water

Step 1: Heating lipid
and aqueous phase

Fig. 3.3 Schematic steps involved in the microemulsion technique