Liposomes formulated with fMLP-modified cholesterol for enhancing drug concentration at inflammatory sites

Improving efficacy of inflammation treatment by increasing drug delivery to the inflammatory sites is a challenging endeavor. N-formyl-methionyl-leucyl-phenylalanine (fMLP), the first discovered leukocyte chemotaxis peptide, is composed of formyl methionine, leucine and phenylalanine. It conjugates with formyl peptide receptors on the target cells with high receptor expression on the surface such as macrophages. With this in mind, we developed a novel fMLP-modified liposome (fMLP-LIP) for enhancing drug delivery to the inflammatory sites and resolving the systemic reaction issue with conventional anti-inflammatory drugs. Being a more stable and cheaper liposomal component than phospholipids, cholesterol (CHO) has been thoroughly investigated as an alternative anchor. In this study, fMLP was covalently conjugated with CHO with polyethylene glycol link to prepare the liposomes, cellular uptake of liposomes by differentiated human U937 cells was examined and cellular uptake experiment in vitro was employed to optimize fMLP-LIP prescription and investigate the uptake mechanism. An in vivo inflammatory model was established to evaluate the targeting performance of fMLP-LIP to inflammatory site. The in vitro and in vivo findings indicate that the fMLP ligands playing an important role in increasing drug delivery to inflammatory sites and fMLP-LIP as a promising anti-inflammatory drug carrier.