2.2.5. In Vitro Release of the FS-NTF-Loaded Hydrogel

In vitro release of the entrapped drug from the developed HA-FS-NTF containing the 0.5% marketed formulation of fluconazole and the suspension containing 0.5% fluconazole was studied using a Type I USP dissolution apparatus (basket type) (DT 700 LH device, ERWEKA GmbH DT 700, Heusenstamm, Germany). The samples were loaded into the respective cylindrical tubes (10 cm in length and 2.7 cm in diameter) and were attached to the apparatus instead of the basket, with the lower end of the tube closed tightly by a semipermeable membrane with a pore size of 100 µm. Before use, the dialysis membrane was activated by placing the dialysis membrane in boiling water containing 1 M NaHCO<sup>3</sup> for 1 h. Thereafter, it was washed thoroughly using tap water and stored in phosphate buffer (pH 7.4) for 1 h. The dialysis membranes were kept in the refrigerator in the phosphate buffer (pH 7.4) media overnight prior to performing the release study.

One gram of each sample was loaded in the cylindrical glass tube assembly as described above. The release study was performed in 250 mL phosphate buffered saline (pH 6.8), which was maintained at a physiological temperature (37 ± 0.5 ◦C) with the rotation of the stirring shaft fixed at 50 rpm. The release study was performed for 3 h, during which time 5-mL aliquots were withdrawn at intervals of 0.0, 0.25, 0.5, 1.0, 1.5, 2.0, 2.5, and 3.0 h. Fresh media were replaced during each withdrawal and maintained at room temperature. The collected samples were filtered using a 0.45-m membrane filter, and the rate of drug release was determined using a UV-visible spectrophotometer at 261.6 nm, with phosphate buffered saline as the blank.
