Targeting liposomes to endothelial cells in inflammatory diseases

The endothelium covers the vascular wall of all blood vessels in the body and comprises 10¹³ endothelial cells (ECs) in an adult (1). Their excellent accessibility for drugs present in the systemic circulation and their involvement in a large variety of physiological and pathophysiological processes make ECs ideal targets for targeted liposome-mediated drug delivery. The heterogeneity of the endothelium with respect to appearance and function allows for drug delivery approaches that are either organ and/or disease specific. Despite these features, research on liposome-mediated drug delivery to ECs is limited. This is undoubtedly related to the fact that ECs are generally refractory to liposome uptake (2) and that the use of specific targeting devices are a prerequisite for liposome uptake by selected cell subsets.