Surfactants consist of a water loving and a water fearing part.
This causes them to aggregate in water in such a way that the water fearing part is shielded from the water and the water loving part is exposed to the water. The surfactants we use are tertiary amines. When tertiary amines are dissolved in an aqueous they are protonated to a certain degree, depending on the pH of the solution. The difference in protonation state as pH is changed has an effect on the aggregation behaviour of these surfactants. This change in aggregate morphology could well explain their effectiveness in bringing DNA in a cell.