Design of immuno-enzymosomes with maximum enzyme targeting capability: effect of the enzyme density on the enzyme targeting capability and cell binding properties

Immuno-enzymosomes have been proposed for the targeting of enzymes to cancer cells to achieve site specific activation of anticancer prodrugs. Previously, we reported that the enzyme beta-glucuronidase (GUS), capable of activating anthracycline-glucuronide prodrugs, can be coupled to the surface of inmunoliposomes directed against human ovarian cancer cells (OVCAR-3). This study aimed at the design of an immuno-enzymosome formulation with maximum enzyme targeting capability. By purification of the commercially available enzyme beta-glucuronidase (GUS), a 2-fold increase in the enzyme specific activity and a 4-fold increase in the enzymatic activity of immuno-enzymosomes was achieved. As a result, upon incubation with human ovarian cancer cells (OVCAR3), cell-associated enzymatic activity increased correspondingly. The optimized immuno-enzymosomes were shown to bind to the target cells in a specific fashion. Above a GUS/Fab' molar ratio of 0.5, impairment of the target cell binding ability of the immuno-enzymosomes was observed. This was likely due to a steric hindrance effect mediated by the presence of large amounts of bulky GUS molecules on the liposome surface. Nevertheless, increasing the GUS density on the surface of the immuno-enzymosomes to levels by far exceeding the GUS/Fab' molar ratio of 0.5, yielded a considerably Improved enzyme targeting capability. (C) 1999 Elsevier Science B.V. All rights reserved

A NEW APPLICATION FOR LIPOSOMES IN CANCER-THERAPY - IMMUNOLIPOSOMES BEARING ENZYMES (IMMUNO-ENZYMOSOMES) FOR SITE-SPECIFIC ACTIVATION OF PRODRUGS

AbstractWe have tested a new type of immunoliposomes which may effectively mediate the targeting of enzymes to be used for site-specific prodrug activation (immuno-enzymosomes). The enzyme β-glucuronidase, capable of activating the prodrug epirubicin-glucuronide (epi-glu), was coupled to the external surface of immunoliposomes directed towards ovarian cancer cells. A significant increase in cytotoxicity of the prodrug epi-glu was shown when the in vitro cultured cancer cells were pretreated with these immuno-enzymosomes

Liposomes: Vehicles for the targeted and controlled delivery of peptides and proteins

Several approaches are presented that have been developed for the liposomal delivery of peptides and proteins. For a rational design of targeted liposomes, the anatomical and physiological constraints with respect to the distribution of liposomes in the body have to be taken into account. Target sites that offer exciting opportunities are located in the blood compartments (e.g. thrombi, endothelium), in the liver (e.g. macrophages), in the peritoneal cavity (e.g. tumor cells), or in diseased tissues (e.g. inflammations or tumors). Examples of ongoing liposome-related research in our institutes are discussed