Effects of Oligodeoxynucleotides on the Physicochemical Characteristics and Cellular Uptake of Liposomes

Abstract

We studied the effects of a phosphodiester oligodeoxynucleotide (ODN), which is antisense to the site in the neighborhood of the AUG initiation codon of the mouse tumor necrosis factor alpha gene (TNF-alpha), on the physicochemical characteristics and the cellular association of three types of liposomes with different surface charges. The physicochemical characteristics of the liposomes changed after adding ODN. When the ODN/lipid molar ratio was approximately 0.15 in cationic (TMAG) liposomes [consisting of N-(alpha-trimethylammonioacetyl)didodecyl-D-glutamate chloride (TMAG), dilauroylphosphatidylcholine (DLPC), and dioleolylphosphatidylethanolamine (DOPE) in a 1:2:2 ratio], but not in neutral and negatively charged liposomes, then the liposomes aggregated and fused. At higher molar ratios, these changes in TMA liposomes were not evident. In addition, ODN inverted the zeta-potential of TMAG liposomes from positive to negative at an ODN/lipid molar ratio of approximately 0.15. Therefore, the aggregation and fusion induced by ODN could be explained by a lower surface charge repulsion between TMAG liposomes. On the other hand, the association of ODN with RAW264.7 cells, a mouse macrophage-like cell line, was very slight. The cellular association of ODN was significantly enhanced compared with neutral and negatively charged liposomes by encapsulation in TMAG liposomes. The ODN added to liposome suspensions did not affect the rate and extent of TMAG liposome cellular association, even at an ODN/lipid molar ratio of approximately 0.15. These results indicate that the lipid composition and ODN/lipid molar ratio are critical for the physicochemical characteristics of cationic liposomes. However, the changes had less influence on the cellular uptake properties of cationic liposomes.

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“…After weekly injections, systemic and local joint secretion of TNF-α was significantly inhibited, as well as IL-6 and MCP-1 (Khoury et al, 2008(Khoury et al, , 2006. However, these complexes usually have high charge density on their surface, which can induce non-specific interaction with serum protein leading to aggregation and further adverse effects (Arima, Aramaki, & Tsuchiya, 1997). To achieve better systemic delivery of siRNA, many authors have considered the use of neutral or even PEGylated lipids to cover liposome surface and reduce protein interactions.…”

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Contribution of Trypsin-Sensitive Proteins to Binding of Cationic Liposomes to the Mouse Macrophage-like Cell Line RAW264.7

“…18 However, the reason for the increase in cellular association of the cationic liposomes has not been wellcharacterized. 18 However, the reason for the increase in cellular association of the cationic liposomes has not been wellcharacterized.…”