VC was determined as described previously [37]. The mobile phase was 0.2% metaphosphoric acid/methanol/acetonitrile (90:8:2, v/v/v) and the retention time was about 3.5 min. The drug content (C1) was assayed by HPLC at room temperature at 250 nm, using a 250 mm × 3 mm Nucleosil® 100-5 C18 packed column. From the data, the drug payload was calculated as the ratio of amount of entrapped drug in nanoparticles (mg) C1/amount of liposomes (mg):