Transferring any protein, DNA or a large molecule through the cell is very difficult. There are two techniques that are very commonly used for this purpose. The one that is used the most in electroporation: in which a defined pulse of current /electricity is passed through the medium to create small holes in the membrane which allow the macromolecules to pass through the membrane. The other used mostly for nucleic acid is lipofectamine which not only allows small molecules to go through the membrane but also allows the molecules to pass through the nuclear membrane and thus enable transformation of the cell.
Mechanical shearing has not been very effective since it causes significant damage and can lead to the death of the cells. A graduate student, Armon Sharei in the lab of Klavs Jensen has observed an interesting effect that passing cells through microfluidic chamber gently causes the transport of surrounding material into the cell. This is a major finding since it allows some cells, that were difficult to transform like the primary cells from an animal, to be transfected. This device is capable of processing nearly 1 million cells at a time and will change the way primary cells are transfected in the absence of any chemicals or electrical damage.
It is interesting to note that a similar effect happens in the capillary as the cells are squeezed through and it is interesting to wonder whether cells pick up other small molecules and compounds as they are circulating. It is even possible to conjecture that the immune system surveillance takes place at the cell membrane level sensing the different molecules present in the mileu but also through taking up some of the foreign proteins or even viruses directly into the cells.
