BLUE LIPOSOMES FOR IDENTIFICATION OF THE SENTINEL LYMPH NODES IN PIGS

Abstract

Effective preoperative staining of regionallymph nodes improves their intraoperativeidentification and thus the selectivity of"sentinel node" lymphadenectomy. Unfortunately,aqueous Patent Blue V (PBV) oftenfails to provide the requisite intensity andduration of contrast (1,2). A comparativestudy of staining characteristics ofPBV inaqueous solution with those of liposomallyencapsulated PBV was carried out on 7femalepigs with an average weight of40 kg. Theliposomes, consisting of lecithin and cholesterolin a molar ratio of3:1, were produced by anextrusion technique using membranes withthicknesses of5pm, 1.2pm, O.4pm and 0.2pm.In each instance, a 0.5-ml depot containing25 ± 0.4 mg ofPBVlml was injected into eachof the four upper and lower mammary glandsin aqueous solution on the left side and in aliposomal preparation on the right side.Stained lymph nodes of the groin, pelvis andneck were identified after 3, 6, 12 or 24 hours,then excised and photographed. Their PBVconcentrations were measured by spectrophotometry.In all cases, the liposomepreparations provided greater intensity and alonger duration than the aqueous solution.Liposomal PBV compared with aqueous PBVcan therefore be recommended for betterpreoperative lymph node staining andidentification of "sentinel" lymph nodes.