Studies on Solid Lipid Nanoparticles (SLN) of Stearic Acid-Effect of Particle Size and Degree of Dispersion on Ultrasonic Velocity

In view of the importance of solid lipid nanoparticles (SLN) as novel delivery systems for pharmaceutical and cosmetic active ingredients, ultrasonic velocimetry was used to study nano suspensions of SLN. The propagation of sound through colloidal systems can probe new properties that characterize both structure and the dynamics of the suspension. Stearic acid (SA) a biocompatible fatty acid was made into SLN by nano precipitation method. In order to have solid lipid nanoparticles of varied sizes, two stabilizer systems, a mixture of cetyl trimethylammonium bromide (CTAB) and 0.3% solution of poly (vinylpyrrolidone) (PVP) (Mw 40 k Da) (stabilizer-I) and a mixture of polyoxyethylene sorbitan fatty acid ester (TWEEN-80) and anionic surfactant sodium dodecyl sulphate (SDS) (stabilizer-II) were used. A correlation between crystallinity of the SLN, particle size and ultrasonic velocity was realized. Dispersion stability was found to be related to certain acoustic parameters. A comparison of effective density and velocity computed according to three theoretical models viz. Urick, Kuster and Toksöz and Urick and Ament was made with experimental values.