Preparation of Targeting Proteoliposome by Postinsertion of a Linker Molecule Conjugated with Recombinant Human Epidermal Growth Factor

To develop a sterically stable, targeting proteoliposome, a postinsertion method was employed to biofunctionalize the liposome surface with a biocompatible anchor molecule (BAM) linker conjugated with epidermal growth factor (EGF) as a homing molecule. In this method, EGF was first conjugated with BAM that consisted of a hydrophilic reactive group at one end and oleic acid chains at the other end. The EGF-BAM complex was then inserted into the liposomal phospholipid bilayer through lipophilic interaction. When compared with the traditional surface modification method by amine coupling, the modification efficiency with BAM at 25 °C was about 2.5-fold higher, and the 24 h stability of the inserted BAM at 25 °C was also about 2.5-fold higher. The insertion affinity and stability of the BAM to the liposomal bilayer was not influenced by an increase in cholesterol concentration, a component in liposome preparation. Confocal microscopy studies showed that the proteoliposomes biofunctionalized with the BAM-EGF complex encapsulating Cy5 fluorescent dye were selectively bound to the surface of MDA-MB-231 cells overexpressing EGFR (epidermal growth factor receptor), but not to MCF-7 cells, which did not express EGFR. The same proteolipome encapsulating doxorubicin was selectively targeted to MDA-MB-231 cells and killed them. In sum, BAM could be used as a suitable postinsertion linker for biofunctionalization of liposome surface with high modification efficiency and stability. Furthermore, the protein used as a homing molecule maintained its bioactivity after the biofunctionalization.