New Material Mimicking Cell Membrane

Scientists in Pacific Northwest National Laboratory (PNNL), USA have developed a new material that works like a cell membrane. The material can assemble itself into an extremely thin sheet that can withstand being submerged in a variety of liquids and even can

repair itself after damage. The study results, published in the journal of Nature Communications, showed that the developed material mimicked the cell membrane making it a synthetic cell membrane-like material.

Artificial Cell membrane (Picture Courtesy: Science Daily)

As we know- naturally cell membranes are made from thin sheets of fatty molecules called lipids. They are at least 10 times thinner than soap bubble and yet allow cells to collectively form organisms as diverse as bacteria, large animals and plants. They are also very selective about what they let pass through, using tiny embedded proteins as gatekeepers. Membranes repair their structure automatically and change thickness to pass signals from the outside environment to the cell’s interior. Moreover, membrane properties such as gatekeeping could be useful for making filters or signaling to make sensors. For example, mimicking a cell membrane’s gatekeeping could result in water purifying membranes that don’t require a lot of pressure or energy to push the water through.

With this in mind, researchers have been investigating synthetic molecules called peptoids, which are cheap, versatile, customizable and similar to natural proteins — including those that embed themselves in cell membranes. Led by Chemist Chun-Long Chen, experimented to see if they could design peptoids to make them more lipid-like. They designed peptoids in which each base peptoid was a long molecule with one water-loving end and one fat-loving end — just like lipid molecules. They then chose chemical features that they anticipated would encourage the individual molecules to pack together. They found that after putting the lipid-like peptoids into a liquid solution, the molecules spontaneously crystallized and formed what the scientists call nanomembranes — straight-edged sheets as thin as cell membranes — floating in the beaker. These nanomembranes maintained their structure in water or alcohol, at different temperatures, in solutions with high or low pH or high concentrations of salts.

During their test to know whether the synthetic membranes had the signaling ability of cell membranes, the researchers added a touch of salt, which is involved in the last step in many signaling sequences and causes real cell membranes to thicken up. The more salt the researchers added, the thicker the nanomembranes became, reaching about 125% of their original thickness in the range of salt concentrations they tested.

It is a matter of fact that real membranes also hold proteins that have specific functions, such as ones that only let water through them. The group tested the ability of peptoids to do so by introducing a variety of side chains — small molecules of different shapes, sizes and chemical natures attached to the longer lipid-like peptoids. In each of 10 different designs, the peptoids assembled into the nanomembranes with the core structure remaining intact. The team also claimed that they can build a carbohydrate into nanomembranes, showing the material can be designed to have versatile functions.

Ultimately, the team 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. It was an amazing discovery! The researchers believe that these new materials have potential in water filters, sensors, drug delivery and especially fuel cells or other energy applications.

Reference

Haibao J.; Fang, J.; Michael, D. D.; Yulin, C.; Feng, Y.; Yan-H, D.; Xin Z.; Ellen J. R.; Marcel D. B.; and Chun-L., C. Highly stable and self-repairing membrane-mimetic 2D nanomaterials assembled from lipid-like peptoids, Nature Comm. 2016, 7, 12252.