THE EFFECT OF THE COMPONENTS OF MICROEMULSIONS ON BOTH SIZE AND CRYSTALLINE-STRUCTURE OF SOLID LIPID NANOPARTICLES (SLN) CONTAINING A SERIES OF MODEL MOLECULES

Solid lipid nanoparticles (SLN) were prepared by dispersing warm oil-i n-water microemulsions in cold water. This study evaluates the influen ce of the microemulsion components on size and crystalline structure o f SLN. Two microemulsion formulations containing stearic acid and wate r were prepared and using different surfactants and cosurfactants. For one, two nonionic molecules, Tween 20 and butanol, were used, and for thr other, two ionic molecules, taurodeoxycholate and monooctylphosph ate as cosurfactants and Epikuron 200 as surfactant were used. Model m olecules incorporated into SLN were a series of polycyclic aromatic hy drocarbons and some derivatives (naphthalene, 2-methylnaphthalene, phe nanthrene 2-methylphenanthrene, 2-hydroxynaphthalene, 9-hydroxyphenant hrene, 1,2-naphthoquinone, 1,4-naphthoquinone). The size of SLN varied with microemulsion composition and the molecules incorporated. The cr ystalline structure was examined by means of thermal analysis; SLN obt ained from the first microemulsion contained only one polymorph of ste aric acid (form C); moreover all model molecules were dispersed in SLN in amorphous state. The SLN obtained from the second microemulsion co ntained the form C of stearic acid and no crystalline features of the model molecules; but in the case of the derivatives containing oxygena ted functions, the B form of stearic acid was present alongside the C form, and the incorporated molecules were crystallized to some extent.