Scientists create synthetic membranes that grow like living cells

June 23, 2015

Growing cell membranes are seen in this time lapse sequence (numbers correspond to minutes of duration) (credit: Michael Hardy, UC San Diego)

Chemists and biologists at UC San Diego have succeeded in designing and synthesizing an artificial cell membrane capable of sustaining continual growth, just like a living cell.

Their achievement will allow scientists to more accurately replicate the behavior of living cell membranes, which until now have been modeled only by synthetic cell membranes without the ability to add new phospholipids.

Structure of a phospholipid, a major component of all cell membranes (credit: Wikimedia Commons)

“The membranes we created, though completely synthetic, mimic several features of more complex living organisms, such as the ability to adapt their composition in response to environmental cues,” said Neal Devaraj, an assistant professor of chemistry and biochemistry at UC San Diego who headed the research team, which included scientists from the campus’ BioCircuits Institute.

“Many other scientists have exploited the ability of lipids to self-assemble into bilayer vesicles with properties reminiscent of cellular membranes, but until now no one has been able to mimic nature’s ability to support persistent phospholipid membrane formation,” he explained. “We developed an artificial cell membrane that continually synthesizes all of the components needed to form additional catalytic membranes.”

Michael Hardy | Autocatalyst Drives Vesicle Growth

A time-lapse video shows increase in vesicle volume and membrane surface area at 60 second intervals over a period of 12 hours (credit: Michael Hardy, UC San Diego)

The scientists said in their paper, published in the current issue of  Proceedings of the National Academy of Sciences, that to develop the growing membrane they substituted a “complex network of biochemical pathways used in nature with a single autocatalyst that simultaneously drives membrane growth.” In this way, they added, “our system continually transforms simpler, higher-energy building blocks into new artificial membranes.”

“Our results demonstrate that complex lipid membranes capable of indefinite self-synthesis can emerge when supplied with simpler chemical building blocks,” said Devaraj. “Synthetic cell membranes that can grow like real membranes will be an important new tool for synthetic biology and origin-of-life studies.”

Support for the research was provided by UC San Diego, US Army Research Laboratory, US Army Research Office, and the National Science Foundation.

Abstract of  Self-reproducing catalyst drives repeated phospholipid synthesis and membrane growth

Cell membranes are dynamic structures found in all living organisms. There have been numerous constructs that model phospholipid membranes. However, unlike natural membranes, these biomimetic systems cannot sustain growth owing to an inability to replenish phospholipid-synthesizing catalysts. Here we report on the design and synthesis of artificial membranes embedded with synthetic, self-reproducing catalysts capable of perpetuating phospholipid bilayer formation. Replacing the complex biochemical pathways used in nature with an autocatalyst that also drives lipid synthesis leads to the continual formation of triazole phospholipids and membrane-bound oligotriazole catalysts from simpler starting materials. In addition to continual phospholipid synthesis and vesicle growth, the synthetic membranes are capable of remodeling their physical composition in response to changes in the environment by preferentially incorporating specific precursors. These results demonstrate that complex membranes capable of indefinite self-synthesis can emerge when supplied with simpler chemical building blocks.