Self-reproducing synthetic cells

Researchers at Harvard University have created polymer-based, cell-like structures capable of self-reproducing—one of the most fundamental characteristics of life. The system does not use any of the carbon-based molecules that life on Earth relies on. The researchers say their work hints at ways that life, though not life as we know it, might exist (Proc. Natl. Acad. Sci. U.S.A. 2025, DOI: 10.1073/pnas.2412514122).

“We asked if biochemistry is necessary to realize the properties of life, or if there exist other types of chemistry that could achieve the same end result,” says lead researcher Juan Pérez-Mercader in an email to C&EN. The answer, he says, is “no—biochemistry is sufficient but not necessary for life.”

Pérez-Mercader says the finding opens the door to artificial life and could also help trace the origins of life by showing that simple chemicals can have lifelike behaviors through self-organized physical laws. The results might also expand the search for alien life by suggesting what hallmarks to look for. “For us, we want to know if we can look for life in the universe—including exoplanets—that is not constrained to biochemistry,” he says.

To build their self-reproduction structures, the team began with an aqueous solution containing monomers to be polymerized, a photocatalyst, and a reversible addition-fragmentation chain transfer (RAFT) agent bound to units of ethylene glycol to create a hydrophilic macro-RAFT agent.

The team placed the solution into a capped vial under a nitrogen atmosphere and then put the vial inside a beaker surrounded by green LEDs to power the reaction. When the researchers switched the lights on for 90 min at 33 °C, the monomers began to polymerize, attaching to the hydrophilic macro-RAFT agent and forming a hydrophobic chain that built off it. This process created amphiphilic block copolymers, which self-organize into cell-like vesicles similar to phospholipid bilayers—fundamental structures in biological membranes.

The team then took a small amount of the mixture and put it under a microscope with a green light. They found that as the polymerization continues, the hydrophobic block grows and the vesicle membrane thickens. This build-up creates internal pressure within the vesicle until shorter amphiphiles are squeezed out of the “parent” vesicle and spread around nearby. There, partially formed amphiphiles continue to polymerize.

As the reaction progresses, more amphiphiles gather together in the solution until they self-organize into new (younger) vesicles—just as their parent did. The cycle continues as long as the light shines and there are monomers to polymerize.

“We seem to have produced in the laboratory an example of non-biochemical life that includes a primitive form of heritable variation,” Pérez-Mercader says. “Not only does this challenge our thinking about life in the universe, it offers opportunities for new nanotechnology fabrication and for applications that imitate what natural life does without using natural life itself,” he adds.

Giuseppe Battaglia, a molecular bionics researcher from the Institute for Bioengineering of Catalonia, who was not involved in the study, says the result supports the notion that adaptation doesn’t happen only in living things—it can also happen in nonliving systems when they’re in the right physical conditions. For example, “one can think of autonomous soft robotics that adapt their shape and function based on environmental stimuli or responsive materials that develop complex, adaptive behaviors without external programming,” he says.