Acta Pharm. 48 (1998) 259-267
Solid lipid nanoparticles (SLN) are an alternative particulate drug carrier
system to polymeric nanoparticles, liposomes and fat emulsions. The aim of our study was to
prepare SLN of different lipids by the melt-emulsification process and estimate their
stability. In order to find the optimal procedure, several dynamic parameters were varied,
including emulsification (time, stirring rate) and cooling conditions. Additionally, the effect
of phospholipid concentration on the mean diameter and zeta potential of SLN was examined.
Particles were characterised by mean size, polydispersity index and zeta potential measurements.
The mean size of the lipid nanoparticles determined by photon correlation spectroscopy varied
from 120 to 220 nm depending on the procedure parameters and composition of the lipid matrix.
We have found that the viscosity of lipid melts affects the SLN size less than procedure
parameters. The optimum procedure parameters need to be assessed for each nanoparticle system
separately. The obtained results indicate that Witepsol® and Dynasan®
SLN remain stable at 4 °C since no pronounced particle growth could be detected over the
monitored period. On the contrary, Compritol® SLN dispersions are remarkably
unstable since the mean particle size increased from 155 nm to 3 mm within one-week incubation
period.
Phospholipids have a specific influence on the formation of SLN. In 1–2%
(m/m) concentration, the stable SLN dispersion is formed, and at higher
phospholipid concentration the liposome formation was stated as well.
Keywords: solid lipid nanoparticles, colloidal drug carrier, phospholipids, viscosity, triglycerides