To better understand the nanomembranes, the team simulated how single peptoid molecules interacted with each other using molecular dynamics software. The simulated peptoids formed a membrane reminiscent of a lipid bilayer: The fat-loving ends lined up in the middle, and their water-loving ends pointed outward either above or below.
To test whether their synthetic membranes had the signaling ability of cell membranes, the researchers added a touch of sodium chloride salt. Salt is involved in the last step in many signaling sequences and causes real cell membranes to thicken up. And thicken up the peptoids did. The more salt the researchers added, the thicker the nanomembranes became, reaching about 125 percent of their original thickness in the range of salt concentrations they tested.
Real membranes also hold proteins that have specific functions, such as ones that let water, and only water, through. Chen's group tested the ability of peptoids to do so by introducing a variety of side chains. Side chains are essentially small molecules of different shapes, sizes and chemical natures attached to the longer lipid-like peptoids. They tried 10 different designs. In each case, the peptoids assembled into the nanomembranes with the core structure remaining intact. The team could also build a carbohydrate into nanomembranes, showing the material can be designed to have versatile functions.
The team then tested the nanomembranes to see if they could repair themselves, a useful feature for membranes that could get scratched during use. After cutting slits in a membrane, they added more of the lipid-like peptoid. Viewed under a microscope over the course of a few hours, the scratches filled up with more peptoid and the nanomembrane became complete again. (Compare this to cuts in paper, which don't spontaneously repair themselves even after being taped up.)
Taken together, the results showed the researchers that they are on the right path to making synthetic cell membrane-like materials. However, there are still some challenges to be addressed for applications. For example, the researchers would like to better understand how the membranes form so they can make many desirable sizes.
The next step, Chen said, is to build biomimetic membranes by incorporating natural membrane proteins or other synthetic water channels such as carbon nanotubes into these sheet matrices. The team is also looking into ways to make the peptoid membranes conductive for energy uses.Reference
Haibao Jin, Fang Jiao, Michael D. Daily, Yulin Chen, Feng Yan, Yan-Huai Ding, Xin Zhang, Ellen J. Robertson, Marcel D. Baer & Chun-Long Chen. Highly stable and self-repairing membrane-mimetic 2D nanomaterials assembled from lipid-like peptoids
, Nature Communications, July 12, 2016, doi: 10.1038/ncomms12252.Source