The production and characteristics of solid lipid nanoparticles (SLNs)

Abstract

Modified high shear homogenization and ultrasound techniques were employed to produce solid lipid nanoparticles (SLNs). Model drug mifepristone had been incorporated in SLNs. The mean particle size measured by laser diffractometry (LD) was found to be 106 nm with a narrow particle distribution of polydispersity index, 0.278. Differential scanning calorimetry and X-ray diffraction measurements suggested that the majority of the SLNs were less ordered arrangement of crystals, and this was favorable for increasing the drug loading capacity. The drug entrapment efficiency (EE%) of SLNs was more than 87 percent and showed relatively long-term physical stability as the leakage was very small after being stored for one month. Therefore, seemed this modified method could prepare high quality SLNs loading lipophilic drugs. It is a simple, available and effective method to produce SLNs.

Introduction

Solid lipid nanoparticles (SLNs), introduced in 1991, for combining the advantages but avoiding the disadvantages of other colloidal carriers [1], [2], [3] have attracted increasing attention in recent years, and are regarded as an alternative carrier system [4], [5] to traditional colloidal systems, such as emulsions, liposomes and polymeric microparticles and nanoparticles.

The predominant production technique till recently was the high-pressure homogenization (HPH) method [6], [7]. However, there were still two other production methods that seemed to be given up by the researchers to produce SLNs. One was the solvent evaporation by precipitation in o/w emulsions [8], [9]. Due to the organic solvents and the large amount of surfactants and other additions introduced, this method has some clear disadvantages. But the other production method of high shear homogenization and ultrasound did not involve organic solvents nor large amount of surfactants nor other additions as the HPH, and both dispersing techniques were initially used for production of SLNs [10], [11]. The above two methods were extensively used and easy to handle. However, these traditional techniques had the disadvantage of low dispersion quality. In order to use these easy and familiar tools that were almost available in every laboratory, the traditional dispersing techniques were modified in this study to produce high quality solid lipid nanodispersion.

The model drug employed here was a lipophilic drug mifepristone [12], an effective abortifacient drug, and its chemical structure is shown in Fig. 1. The drug had a poor water solubility and high lipophilicity like steroid drug mifepristone that made it an excellent candidate for SLNs encapsulation.