the present invention describes a composition consisting of liposomes covalently or non - covalently coupled to the glycoprotein streptavidin . the streptavidin may additionally be coupled to biotinated proteins such as immunoglobulin g or monoclonal antibodies . the liposomes of the invention may have a transmembrane potential across their membranes , and may be dehydrated . in addition , the composition may contain ionizable bioactive agents such as antineoplastic agents , and may be used in diagnostic assays . this is a divisional application of copending application ser . no . 941 , 913 , filed dec . 15 , 1986 , which is now u . s . pat . no . 4 , 885 , 172 , which is a continuation - in - part of copending application ser . no . 811 , 037 , which in turn is a continuation - in - part of copending application ser . no . 749 , 161 , filed june 26 , 1985 , both now abandoned and copending application ser . no . 759 , 419 , filed july 26 , 1985 now u . s . pat . no . 4 , 870 , 635 .