A novel method to produce solid lipid nanoparticles using n-butanol as an additional co-surfactant according to the o/w microemulsion quenching technique

• Microemulsion formulations with different amounts of surfactant and lipids.
• Preparing lipid nanoparticles using microemulsion quenching process.
• Preparation of lipid nanoparticles using low energy and simple instruments.
• A cost-efficient and reproducible preparation of SLN/NLC.

Solid Lipid Nanoparticles (SLN) and Nanostructured Lipid Carriers (NLC) are novel medicinal carriers for controlled drug release and drug targeting in different roots of administration such as parenteral, oral, ophthalmic and topical. These carriers have some benefits such as increased drug stability, high drug payload, the incorporation of lipophilic and hydrophilic drugs, and no biotoxicity. Therefore, due to the cost-efficient, proportionally increasable, and reproducible preparation of SLN/NLC and the avoidance of organic solvents used, the warm microemulsion quenching method was selected from among several preparation methods for development in this research.To prepare the warm O/W microemulsion, lipids (distearin, stearic acid, beeswax, triolein alone or in combination with others) were melted at a temperature of 65 °C. After that, different ratios of Tween60 (10–22.5%) and glyceryl monostearate (surfactant and co-surfactant) and water were added, and the combination was stirred. Then, 1-butanol (co-surfactant) was added dropwise until a clear microemulsion was formed and titration continued to achieve cloudiness (to obtain the microemulsion zone). The warm o/w microemulsions were added dropwise into 4 °C water (1:5 volume ratio) while being stirred at 400 or 600 rpm. Lipid nanosuspensions were created upon the addition of the warm o/w microemulsion to the cold water. The SLN were obtained over a range of concentrations of co-surfactants and lipids and observed for microemulsion stability (clearness). For selected preparations, characterization involved also determination of mean particle size, polydispersity and shape. According to the aim of this study, the optimum formulations requiring the minimum amounts of 1-butanol (1.2%) and lower temperatures for creation were selected. Mono-disperse lipid nanoparticles were prepared in the size range 77 ± 1 nm to 124 ± 21 nm according to a laser diffraction particle size analyzer and transmission electron microscopy. This method for preparing lipid nanoparticles by warm o/w microemulsion quenching was found to be more cost efficient and proportionally increasable in comparison with other preparation methods such as high pressure homogenization. These lipid nanoparticles, due to the combination of hard lipids with soft and/or liquid lipids, become good candidates for a wide range of medicaments as carriers for pharmaceutical and medicinal purposes.