Authors: B. Tenchov, R. Koynova, R. Ahn, T. O’Halloran, R.C. MacDonald
Affilation: Ohio State University College of Pharmacy, United States
Pages: 342 - 345
Keywords: cationic, phospholipid, protamine, carrier, oligodeoxynucleotide
The use of cationic lipid and peptide compounds as carriers for the intracellular delivery of oligodeoxynucleotides (ODNs) with important regulatory functions is of high current interest. Here we used X-ray diffraction, fluorescence resonance energy transfer, dynamic light scattering and zeta-potential measurements to characterize the stability of ODN complexes with cationic phopsholipids and with a native cationic peptide, protamine. The most important observations can be summarized as follows: 1) ODN/protamine complexes with positive zeta-potentials gradually increase in size in the course of hours and days, while the size of complexes with negative zeta-potentials remains constant. 2) The ODNs form stable complexes with protamine and cationic phospholipids at salt concentrations below ~0.5 and ~0.3 M NaCl, respectively. At higher salt concentrations the complexes dissipate and release the ODN molecules. 3) The ODN lipoplexes are typified by tightly packed lamellar phases and disordered ODN arrangements between the lipid bilayers. The lamellar phase spacings were virtually identical, or slightly smaller, by ~0.2 nm, than those of high molecular weight DNA lipoplexes. 4) There are significant differences between ODN/lipid and ODN/protamine particle size distributions. The former displayed a characteristic maximum at cationic/anionic 1:1 charge ratio, while the latter were not influenced by variations of the ODN/protamine ratio.