2.1. SLN Preparation

SLNs were prepared by a fusion-emulsification method as described elsewhere [6]. In short, 300 mg of lipid (Compritol^® 888 ATO) and different amounts of etofenamate or ibuprofen were taken in a 50 mL beaker (oil or lipid phase). The aqueous phase consisted of 10 mL of 2% (w/w) Tween^®80 aqueous solution. Both the aqueous phase and the lipid phase were placed in a water bath (Water Bath VWR 6, VWR, Darmstadt, Germany) at 80–90 °C. After the fusion of the lipids, the aqueous phase was added under high stirring (Silverson SL5M, Silverson LDT Machines, Chesham, UK) at a speed of 12,500 rpm for 10 min. The preparation was removed from the bath, cooled in ice for solidification. Nanoparticles were stored at 4 °C until further use.