Preparation and in vitro evaluation of anti-VCAM-1-Fab''-conjugated liposomes for the targeted delivery of the poorly water-soluble drug celecoxib

When an inflammatory stimulus is given, vascular endothelial cells express various cell adhesion molecules including the vascular cell adhesion molecule (VCAM)-1. In this study, the possibility of specifically delivering anti-inflammatory drugs to activated endothelial cells by utilizing VCAM-1 as a target receptor was explored by loading celecoxib, a selective cyclooxygenase-2 inhibitor, into liposomes coupled to the Fab'' fragment against VCAM-1. Anti-VCAM-1-Fab''-conjugated liposomes were prepared by forming an amide linkage between amino groups of Fab'' and the carboxylic group of glutaryl-N-phosphatidylethanolamine in liposomes using 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide as a cross-linker in the presence of sulpho-N-hydroxysuccinimide. The coupling of Fab'' to phospholipids constituting liposomes was confirmed by SDS-PAGE analysis. Under our optimized conjugation conditions, 130.0 mu A mu g Fab'' was coupled to 1 mu A mu mol liposomes. Immunoblotting analysis showed that VCAM-1 protein expression could be induced by incubating human umbilical vein endothelial cells (HUVEC) with TNF-alpha alpha. Confocal laser microsopy analysis revealed that Fab'' conjugation to liposomes selectively increased liposomal uptake in TNF-alpha alpha-pre-stimulated (VCAM-1-expressed) HUVECs, but not in cells without VCAM-1 expression. The concentration of celecoxib loaded in Fab''-conjugated liposomes was 281.1 +/-+/- 29 mu A mu g/mL, suggesting that liposomal loading also helped to overcome the limitations in celecoxib administration caused by its poor water solubility. Celecoxib loaded in Fab''-conjugated liposomes inhibited prostaglandin E(2) (PGE(2)) production induced by TNF-alpha alpha-pre-stimulation more efficiently than when loaded in conventional liposomes. Therefore, Fab''-conjugated liposomes served as a drug delivery system with dual functions: targeted delivery and solubilizing capacity.