Lymphatic uptake and biodistribution of liposomes after subcutaneous injection. II. Influence of liposomal size, lipid compostion and lipid dose.

The present paper reports on the results of a systematic study on liposome variables potentially affecting lymphatic disposition and biodistribution of liposomes after sc injection. Liposomal size was found to be the most important factor influencing lymphatic uptake and lymph node localization of sc administered liposomes. Lymphatic uptake from the s.c. injection site of small liposomes (about 0.04 microm) was relatively high (76% of the injected dose (%ID)) as compared to large, non-sized liposomes, which remained almost completely at the site of injection. Small liposomes were less efficiently retained by regional lymph nodes than larger liposomes. Liposomal lipid composition did not influence lymphatic uptake with one exception: Lymphatic uptake was decreased in case of neutral liposomes composed of (DPPC). Lymph node localization was substantially enhanced by inclusion of phosphatidylserine (PS) into the liposomal bilayers. Saturation of lymphatic uptake and lymph node localization did not occur over a large liposomal lipid dose range, illustrating the efficient performance of lymph nodes in capturing s.c. administered particles.