2.6. In Vitro Release Study

The in vitro release profiles of SVT from the formulations were determined by using the dialysis bag method. Briefly, 1 mL of each sample was placed in a dialysis bag (14 kDa molecular weight cut-off, Sigma-Aldrich, St. Louis, MO, USA) and suspended into 100 mL of SNES containing 0.5% of polysorbate 80, to improve SVT solubility and to reach the sink conditions. A free drug solution was placed in the dialysis bag in the control experiment (SVT_solution, simvastatin dissolved in 1% ethanol and 0.5% polysorbate 80). The dialysis bags were maintained in the medium under stirring, and maintained in a temperature-constant water bath (37 °C). One milliliter of release medium was collected at predetermined time intervals (from 0.16 to 8 h) and filtered (0.45 µm, Millipore^®). The volume was replaced by adding one milliliter of fresh release medium pre-heated at 37 °C. The samples were analyzed by HPLC–UV, and the cumulative drug release was determined.