Interactions between Cationic Vesicles and Cultured Mammalian Cells

The interaction of small cationic vesicles composed of dioctadecyldimethylammonium bromide (DODAB) with normal versus transformed mouse fibroblasts is described using cell microelectrophoresis, turbidimetry, and cell viability assays over a wide range of DODAB concentrations (10-7−10-3 M). Normal and transformed cells (104 cells/mL) attain a point of zero charge at, respectively, 18.0 and 1.6 μM DODAB. Further increasing DODAB concentration (C) generates positively charged cells. At 105 cells/mL and C ≥ 50 μM, DODAB induces cell−cell adhesion. For transformed and normal cells, peak adhesion occurs at 100 and 1000 μM DODAB, respectively. Upon 0.5 h interaction time with 100 μM DODAB, at 104 cells/mL, 20% of cell death is obtained for normal cells whereas transformed cells remain unaffected. Transformed cells have a higher affinity for DODAB vesicles than their normal counterparts but are more resistant to DODAB-induced cell death. The results indicate that DODAB vesicles interact with cells with very high affinity at low ionic strength and are not toxic below 1 mM, suggesting that they might successfully deliver oppositely charged proteins or DNA strands to cells. These results may be of importance for liposome-mediated processes currently being used for drug or gene delivery to cells.