Serum-resistant lipoplexes in the presence of asialofetuin.

Vectors proposed for gene delivery generally fall into two categories: viral and nonviral. They differ primarily in their assembling process. A viral vector is assembled in a cell, whereas a nonviral vector is constructed in a test tube. While vectors based on viral-based delivery systems are related to safety concerns, immune response, and formulation issues, the problem of nonviral ones is related to their low efficiency for encapsulating large DNA molecules, which has been an important technical obstacle to their utilization. Moreover, for most nonviral vectors, high efficiency in vitro transfection correlates with a global excess of cationic charges. This excess can in vivo facilitate nonspecific interactions with many undesired elements such as extracellular matrix and negatively charged serum components. Scientists have been using liposomes for gene delivery since the late 1970s. However, it was only after the introduction of cationic liposomes, which were shown to complex DNA and form the termed "lipoplexes," which offered some promise for an easy and efficient liposomal gene delivery. In this protocol, we describe the preparation of serum-resistant lipoplexes in the presence of the ligand asialofetuin (AF), in order to design efficient gene therapy carriers to deliver genes to the liver. It is also interesting to note, that although most of the current protocols imply covalent binding of the ligand, our complexes have been formulated by simple mixing of the three components in a studied and established order of addition. Lipoplexes containing the optimal amount of AF (1 microg/microg DNA) showed 16-fold higher transfection activity in HepG2 cells than nontargeted (plain) complexes.