Innovative Production of Diclofenac Sodium-Loaded Solid Lipid Nanoparticles by Membrane Nanoprecipitation: Evaluation of Encapsulation Efficiency and Photoprotection Ability

PURPOSE: The stability of diclofenac sodium (DS) in liquid formulation is influenced by environmental factors such as temperature, humidity and light. The encapsulation of this drug in solid lipid nanoparticles (SLNs) can offer a useful strategy to protect it from degradation. The present study shows the potential of membrane nanoprecipitation (MN) as a productive and advantageous method for the formulation of cocoa butter-based SLNs to improve the photostability of DS. METHODS: Conventional batch nanoprecipitation and MN were explored by varying the formulation parameters and process conditions to obtain SLNs. RESULTS: The MN produced SLNs with an average size of 421 ± 14 nm, a high encapsulation efficiency of 95 ± 3.2%, and a drug loading of 8.8 ± 0.2%, when an acetate buffer at pH 4.1 was used as the non-solvent phase. Chemical characterization of the proposed formulation was performed by DSC and FTIR analyses. The efficacy of SLNs in preserving DS stability was investigated under simulated sunlight exposure, demonstrating a residual drug concentration of 90% after 3.34 min with respect to the aqueous solution that showed the same concentration value after 0.072 min. CONCLUSIONS: Overall, MN represents a suitable and sustainable process for the continuous production of light-stable drug-loaded SLNs.