Methods and Protocols to Make Your Life Easier (3): Microfluidic Transfection
(March 5th, 2013) Not happy with current methods for intracellular delivery? No reason to cry, here’s the latest one using microfluidics! All it needs is a good squeeze...
“By getting stuff into the cells, you can understand the disease and hence design therapies,” says Armon Sharei, lead author of a recent article on a new and vector-free microfluidic transfection technique, addressing the transfection challenge.
Being in the groups of Robert Langer and Klavs Jensen at the MIT, the chemical engineer collaborated across disciplines to develop this new platform for delivering various entities, like nucleic acids, proteins, drugs and nanoparticles into hard-to-transfect human cells, such as immune cells. Armon recalls, “We began to develop, essentially, a miniaturised water gun to shoot material[s] into the cells. [But] this system did not behave as expected and we eventually figured out that squeezing a cell hard enough can cause disruptions in its membrane.”
The team has microfabricated channels on a chip with constrictions in parallel and in series. With controlled pressure, the cells can be passed through these channels at curbed speed. The cells squeeze themselves through the constrictions to make transient membrane pores. On the other side of the chip, the “opened cells” are ready to take up the desired entities. The team had designed the constrictions within the microchannels in parallel to achieve high throughput and in series to obtain accuracy.
“From our initial observations we thought we may have a novel and unique approach that overcomes many challenges. So, over time, we had more experts to test and improve the prototype further,” Armon reflected. The team has systematically validated the fidelity, accuracy, reliability, reproducibility and versatility (for many cell types) of this method, using various other techniques such as confocal microscopy, flow cytometry, Western blotting and Raman spectroscopy.
Frankly, Armon notes on the disadvantages that “we may or may not overcome certain shortfalls with further development. However, we think to improve it for many applications, overall”. So, even though it all sounds very promising, it is not yet time to throw away existing technologies, like, for example, transfecting DNA into immortalised cell lines using lipofectamine or viruses. “Larger molecules, such as plasmids, will not be transported very efficiently,” Armon admits. “Moreover, the technique is not yet optimised for a direct nuclear delivery.” However, he emphasises, “This reasoning may not hold true in the case of patient-derived cells.”
Armon is pretty certain that a better understanding of the mechanism of membrane disruption in terms of constriction dimensions and buffer conditions will help to build better devices for a multitude of applications. How about the most common application: transfection of bacteria? Armon is a bit worried about testing this technique on bacterial cells, as no one knows yet how the bacterial cell wall and membrane repair machinery will react to the mechanical stress. Nevertheless, Armon’s team is certain to test it sooner or later.
The team also invites more collaborators not only to try the device but also to widen the device’s applicability. Some of their goals include the unravelling of disease mechanisms by using nanomaterials to track cellular components and probe the chemical niche of the cells, the transformation of adult human cells into induced pluripotent stem cells and the delivery of drugs directly to immune and cancer cells.
With a valuable and “fairly easy-to-use” device under their belt, Armon Sharei’s team is now exploring the possibility of commercialising their technique. By the way, the microchannelled chips can already be bought from a German company. If their invention thus makes Armon’s cash register ring... we shall have to wait and see!
Vijay Shankar Balakrishnan
Photo: Armon Sharei with the chip, Chris Schlag (cartoon)