Nanoscale DNA - Zwıtterionıc Vesicle Formulation Compacted For Gene Delivery: Adiabatic Differential Scanning Calorimetric Study

Abstract

Nucleic acids-membrane associations comprise the least functionally studied macromolecular assembly, yet attract the attention of researchers due to their potential in the field of gene therapy (Leckband & Israelashvili, 2001). The design of novel nucleic acid delivery formulations proceeds mainly as searches of alternatives to highly efficient but risky viral based vehicles (Templeton, 2001; Liu & Huang, 2002; Miller, 2003). The main objective is to achieve compaction of genetic material within highly restricted compartments, while decreasing its cytotoxicity. In the light of well-established potential of liposomes as gene carriers (Templeton, 2001), the current work concerns mainly the stability and physical properties of DNA within the lipid surrounding. Such particles, referred to as lipoplexes are composed of positively charged lipid species and a helper neutral lipid, used for the stabilization of the liposome complex. Despite the considerable efforts that had been made to characterize the structure of these complexes, the origin of molecular forces responsible for self-assembly formation, determination of their charge, colloidal properties, stability against dissociations, cytotoxicity issues, and unravelling characteristics related to efficient intracellular delivery and gene expression remain unclear. A possible alternative to the toxic cationic lipids is the employment of zwitterionic lipid species, which are much safer for target cells (Kharakoz, 1999). Neutral liposomeDNA self-organization is mediated by various inorganic cations, acting as condensing agents. In the light of recent strong evidence that divalent cations enhance the efficacy of plasmid DNA-cationic lipid formulations (Lam & Cullis, 2000), it is of particular interest to study the effect of different divalent cations on the transfection potency of lipid-DNA complexes. In this context, a preliminary results of promissimg ternary DNA-DPPC-Mg 2+ complex preparation and its thermodynamic properties are presented herein.