Evaporative drying of aqueous dispersions of solid lipid nanoparticles

Solid lipid nanoparticles (SLNs) have been proposed as alternative colloida l drug carriers. SLNs are obtained by dispersing warm oil-in-water microemu lsions into cold water. The aim of this research was to investigate an evap orative drying process for aqueous dispersions of SLNs. For this purpose, a special apparatus, namely, a thermostatic minidesiccator having alumina as the drying medium, was designed to carry out the evaporative drying at a c ontrolled temperature. Besides the water removal kinetics, the mean particl e size and the size distribution of SLNs were measured during the drying wi th the aim of detecting the highest temperature at which the drying process can be carried out without significantly affecting the SLN average diamete r. The SLN dispersions were evaluated with and without a hydrophilic excipi ent, commonly used as a cryoprotector (trehalose). The drying temperature o f 10 degreesC was found to be the most suitable for obtaining SLNs as a pow der, maintaining almost the same size as that of the SLNs in dispersion.