2.5. In Vitro Release Studies

The in vitro release studies were performed by placing the sample filled tubes in a rotary shaker (37 °C, 60 rpm). The drug (Ara-C or DNR) content in the supernatant of each tube was evaluated by UV-vis spectrometer after incubation for 0.5, 1, 12, 24, 36 or 48 h. Equal amounts of PBS (2 mL) were then added into the tubes. The concentration of DNR in the PBS was calculated through the following standard curve: Y = 46.1316X + 0.1796 (R² = 0.9998), where Y is the concentration of DNR (µg/mL) and X is the absorption of DNR in PBS at 484.4 nm. The amount of Ara-C was calculated by the double-wave method, with the standard curve equation: Y = 50.1865X + 0.0166 (R² = 0.9999), where Y is the concentration of the mixture (µg/mL) and X is the absorbance of the mixture in PBS at 271.4 nm. All assays were performed in triplicate.