Preparation and Characterization of Folic Acid-Encapsulated

Background and purpose: Folic acid is a member of the vitamin B family, in acid form has low solubility in water. Folic acid degrades rapidly under exposure at extreme environment like temperature, light, oxygen, low or high pH, and in the presence of other compounds such as riboflavin which is combined in the multivitamin preparations. Various methods have been developed to improve solubility of drugs in water and to increase their stability. Aim of this study is to develop Solid Lipid Nanoparticles (SLN) in order to increase solubility and stability of folic acid. Methods: SLN was developed by microemulsion o/w technique. SLN characteristics were influenced by formulation and process factors. Type of lipids, type of surfactants, and ratio of drug, lipid, and surfactant were formulation variables influencing the SLN. Whereas process factors included homogenization rate, type of homogenizers, and condition of emulsification and solidification. Size and particles morphology of SLN were determined by Scanning Electron Microscope (SEM). Entrapment efficiency of folic acid in the SLN was measured by High Performance Liquid Chromatography (HPLC). Results: microemulsion as an intermediate system of SLN could be formed with composition of stearic acid 1.5%, Pluronic F127 10%, ethanol (95%) 10%, and folic acid 0.015%. Emulsification rate at 500 rpm for 5 minutes at ±65°C and solidification process of microemulsion by dispersion microemulsion in water ±5°C for 10 minutes resulted in spherical particles in the range of 50-200 nm with the entrapment efficiency 12.82%. Conclusions: folic acid-containing SLN has been developed. Critical factors including type of lipids, type of surfactants, ratio of drug, lipid, and surfactant, homogenization rate, type of homogenizers, and condition of emulsification and solidification influenced the characteristics of SLN. Folic acid-containing SLN showed spherical shapes and had particle size of 50-200 nm. The entrapment efficiency of folic acid in SLN was 12.82%. This low entrapment efficiency of folic acid in SLN may due to low solubility of the compound in the lipid. We therefore suggest for further study to use more appropriate lipid to improve the drug-loading capacity of SLN.