Dolores Polo

Biodistribution study of doxorubicin encapsulated in liposomes: influence of peptide coating and lipid composition.

Abstract In this paper we describe the biodistribution of doxorubicin (DXR) encapsulated in three different types of liposomes. Common composition was hydrogenated phosphatidylcholine (HPC)/phosphatidylglycerol (PG) cholesterol (Chol)/X, X being either 10% N‐glutaryl phosphatidylethanolamine (NGPE), 10% NGPE + 6% distearoyl‐phosphatidylethanolamine‐polyethyleneglycol 2000 (DSPE‐PEG), or 10% NGPE + 6% DSPE‐PEG‐COOH. These series of vesicles were coated with an active or an inactive sequence of laminin (laminin receptors, integrins, are over‐expressed in tumor cells). Single doses of these preparations were injected, i.v., into healthy mice. For biodistribution experiments, mice were sacrificed at three different time‐points post‐treatment. Doxorubicin and doxorubicinol (DXOH) levels were determined in plasma, heart, lung, kidney, spleen, and liver using HPLC with daunorubicin (DNR) as internal standard. The results obtained indicate that compositions containing DSPE‐PEG have the longest half‐lives in plasma, as was to be expected according to the data in the literature. However, the presence of the peptides on the surface of liposomes reduces concentration values in this tissue. Distribution in other organs reveals high differences, among the liposomal samples studied, depending mainly on the presence of active or inactive peptide on the surface of vesicles. Liposomes coated with the laminin active sequence show lower accumulation in studied tissues than free DXR. This indicates that heart toxicity, associated to DXR treatments, could be diminished, and open promising perspectives for its future study in tumor‐bearing animals.

OPTIMIZATION STUDY OF DOXORUBICIN LIPOSOMAL PREPARATIONS COATED WITH LAMININ FRAGMENTS

ABSTRACT Immunoliposomes, coated with two peptide sequences and loaded with doxorubicin, were prepared. The influence of different parameters in the sequential steps of liposomal preparations was studied as, for instance, lipid composition, size reduction methods, elimination of non-entrapped drug, and peptide coating sequence. Results were evaluated, such as entrapment efficiency, phospholipid/drug and phospholipid/peptide relationship, and size of final preparations. Effective size reduction was only achieved through probe sonication and the presence of peptides on the surface of liposomes, which does not modify, significantly, the final phospholipid/drug relationship, related to the initial values; however, they promoted a slight increase in the size of final preparations. Dialysis was the most suitable method to wash liposomes from reactants, drug and peptides, as well as being the cleanest process to avoid microbial contamination without significant dilution. Peptide coating yields were similar for liposomal compositions presenting free carboxyl groups on the surface. As determined by other authors, the presence of polyethylene glycol monomethoxy chains on the surface reduces the reactivity of NPGE carboxylic groups.