Galactosylated liposomes for targeted encapsulation and enhanced cytotoxicity of Mistletoe Lectin, an antitumoral type 2 ribosome-inactivating protein.

The development of efficient liposomal encapsulations of proteins for pharmaceutical applications is limited by several factors: their high molecular weight, interactions with surrounding substances, or the generally lower stability compared to small molecules. In this work, various liposomal formulations were prepared using the thin-film hydration method followed by extrusion, to investigate their suitability for the encapsulation of the plant-derived antitumoral mistletoe lectin-1 (ML-1). This can be significantly optimized by exploiting its preferential binding to galactose-containing structures, such as modified lipids integrated into the liposomal bilayer. Incorporation of the galactosylated lipid DSPE-PEG2k-Gal into the membrane significantly enhanced the overall recovery rate and encapsulation efficiency of ML-1, attributed to its affinity for the functionalized component. Compared to non-functionalized liposomes, a 2-fold to 4-fold increase in percentage encapsulation efficiency was observed. The galactosylated lipid optimized the ratio of encapsulated to surface-adsorbed ML-1 and facilitated its preferential localization within the core of the liposomes. A strong correlation was identified between the number of entrapped ML-1 molecules per liposome and the degree of galactosylation. The formulations demonstrated high in vitro cytotoxicity, as exemplified with murine colon-26 carcinoma cells, with the galactose-functionalized liposomes achieving an IC