Intracellular trafficking of cationic liposome-DNA complexes in living cells.

Three-dimensional single-particle tracking (SPT) was used to calculate the mean square displacement (MSD) and the diffusion coefficients of multicomponent cationic liposome-DNA complexes (lipoplexes) in CHO-K1 living cells. In untreated (NT) control cells, we found that the intracellular lipoplex motion was either directed or Brownian with active transportation being definitely more frequent (more than 70%) than Brownian diffusion. The MSD analysis was supported by the calculation of the three-dimensional asphericity, A(3), which was close to unity, denoting the preponderant occurrence of movement along a direction. To elucidate the role of the cytoskeleton structure in the lipoplex trafficking, cells were treated with cytoskeleton (actin microfilaments and microtubules) polymerization inhibitors (latrunculin B and nocodazole, respectively). When cells were treated with inhibitors, the lipoplex movement tended towards a random walk at the expense of directed motion. The disassembly of microtubules had a stronger effect on the reduction of directional movement than that of actin microfilaments. Relevance of the results for enhanced gene delivery is discussed.