In this study, the clot accumulation properties of liposome-coupled plasminogen were compared to those of free (non-liposomal) plasminogen in an in vitro, closed-loop, flow-system. After introduction of a clot into the closed system, double-radiolabelled plasminogen-liposomes were administered and the accumulation of radiolabel on the entire clot was measured.
Liposomal plasminogen showed improved accumulation over free plasminogen, on both a fibrin clot and a whole blood clot. Moreover, once liposomal plasminogen was fibrin associated, it could not be washed away with buffer, in contrast to free plasminogen. Liposomal plasminogen was able to compete successfully with an excess of free plasminogen. The plateau levels for the accumulated amount of plasminogen depended on the incubated amount of plasminogen and were influenced by partial degradation of the clot. Furthermore, it was shown that a threshold liposomal plasminogen surface-density was needed for optimum clot accumulation.
*Participant in the Groningen Utrecht Institute for Drug Exploration, GUIDE
References
1
Crommelin DJA,
Schreier H.
Liposomes. In: Colloidal drug delivery systems.
Kreuter J.
ed.
New York: Marcel Dekker Inc; 1994. pp 73-90.
3
Heeremans JLM,
Kraaijenga JJ,
Los P,
Kluft C,
Crommelin DJA.
Development of a procedure for coupling the homing device Glu-plasminogen to liposomes. Biochim Biophys Acta 1992; 1117: 258-64.
4
Heeremans JLM,
Crommelin DJA,
Kluft C.
Pharmaceutical composition for site-specific release of a clot-dissolving protein. Internat. Patent Appl. No. WO 94 / 07537, 1994.
7
Martin FJ,
Papahadjopoulos D.
Irreversible coupling of immunoglobulin fragments to preformed vesicles. An improved method for liposome targeting. J Biol Chem 1982; 257: 286-8.
11
Fraker PJ,
Speck JC.
Protein and cell membrane iodinations with a sparingly soluble choloroamide, 1,3,4,6,-tetrachloro-3a, 6a-diphenylglycoluril. Biochem Biophys Res Commun 1978; 80: 849-57.
12
Duncan RJS,
Weston PD,
Wrigglesworth R.
A new reagent which may be used to introduce sulfhydryl groups into proteins, and its use in the preparation of conjugates for immunoassay. Anal Biochem 1983; 132: 68-73.
14
Thorsen S.
The mechanism of plasminogen activation and the variability of the fibrin effector during tissue-type plasminogen activator-mediated fibrinolysis. Ann N Y Acad Sci 1992; 667: 52-63.
18
Wasser MNJM,
Nieuwenhuizen W,
Pauwels EKJ.
Scintigraphic detection of thrombi using a Tc-99m labelled antifibrin monoclonal antibody: experiments in vitro and in animals. Proc symposium Clinical use of monoclonal antibodies. Amsterdam: 1988: 122.