Drug targeting to inflammation: studies on antioxidant surface loaded diclofenac liposomes

Inflammation is associated with enhanced vascular permeability, production of inflammatory markers and over production of reactive oxygen species (ROS) with depletion of endogenous antioxidants. Several drug targeting approaches to inflammation taking clues from these events have been evolved. Surprisingly, a drug targeting approach utilizing abundant oxidative stress at inflammatory site has not been followed. Antioxidant surface loaded liposomes might preferentially localize at inflammatory sites via redox interaction where at high level of ROS exist. The present study was focused to investigate the role of antioxidant as a targeting ligand on the surface of liposome employing rat granuloma air pouch model of inflammation. We developed conventional and antioxidant loaded diclofenac (DFS) liposomes (co-enzyme Q10 and ascorbyl palmitate) for i.v. administration and characterized for vesicle size, zeta potential and percent entrapment. In vivo drug targeting studies showed an increase in AUC, therapeutic availability of DFS in air pouch fluid (APF) and APF/serum DFS concentration ratios from antioxidant loaded liposomes compared to conventional liposomes and drug solution. The promising results suggest the role of antioxidant as a possible ligand in drug targeting to a site where at abundant ROS exist.