Characterization - Lipid Nanoparticles: Production, Characterization and Stability - page 52

Fig. 4.3 Cryo-TEM images of nanoemulsions ( a ), solid lipid nanoparticles ( b ) and nanostructured
lipid carriers ( c and d ). (Composition: Nanoemulsion—10 % Miglyol 812; SLN—10 % Compritol
888 ATO; NLC—Compritol 888 ATO: Miglyol (9:1 or 7:3); all stabilized with 10 % Poloxamer
188). Nanoemulsions appeared as droplets, SLN appear as needles ( side view ) or circles ( top view ),
NLC appear as platelets or nanospoons ( side view ) or circles with Miglyol sticking to surface ( top
view ). Reprinted from J Control Rel, Jores et al. ( 2004 ), with permission from Elsevier
or without praziquantel. The particles are usually dried by freeze drying, and their
surface is coated with a conducting material such as gold by sputtering.
A major drawback to the technique is that the sample preparation procedures,
specifically application of vacuum, may affect the nature of the particles, leading to
uncertainty in the experimental observations. This is particularly true in the case of
cryo-SEM techniques (as in Fig. 4.6 ) where freezing must be very quick if artefacts
such as salting out of electrolyte during the freezing process are to be avoided.
Cryo-field emission SEM (cryo-FESEM) is another imaging technique used to
investigate the ultrastructure of the solid dispersions. Solid particles can be viewed