A novel method to prepare highly encapsulated interferon-α-2b containing liposomes for intramuscular sustained release

Abstract A novel modified film-hydration–dilution method was employed to prepare highly encapsulated interferon-α-2b containing liposomes for intramuscular sustained release. The liposomes produced by this technique were a mixture of mainly unilamellar vesicles and a small number of multilamellar vesicles. The trapping efficiency was above 80%. With at least 60-fold dilution, Triton X-100 at the concentration of 0.3% (w/v) in phosphate buffered saline (PBS) was able to solubilize phospholipids without denaturing the protein and/or interfering with the enzyme-linked immunoassay (ELISA). After three homogenization cycles under a pressure of 70 MPa the size of liposomes was reduced from 978 to 101 nm while the activity of interferon-α-2b decreased by 9.9% compared to the control. Although liposomes were physically stable for 22 months at 4 °C the mean size of the liposomes increased slightly from 101 to 122 nm. The levels of free interferon-α-2b at the site of intramuscular injection decreased rapidly with only 4.15% of initial dose retained at the injection site after 0.33 h following injection of an interferon-α-2b solution (nonencapsulated). In contrast, interferon-α-2b encapsulated in liposomes was retained at the site of intramuscular injection at higher levels than free interferon-α-2b ( p