Zwitterated Interfaces

Nature has figured out how to reduce nonspecific adsorption by presenting zwitterion groups to the outside world. In fact, about 75% of the phospholipids making the outside of a mammalian cell membrane bilayer are zwitterionic, meaning they have head groups with perfectly balanced positive and negative charge. Phosphatidylcholine has the phosphorylcholine head group.

We mimic this with the sulfobetaine group, shown below, which we incorporate into multilayer coatings. In this example, protein and cell adhesion to the surface are completely prevented.

Here is an example of a copolymer with the sulfobetaine group which we synthesize in our lab: