Membrane functions genetically programmed in synthetic cells: A barrier to conquer

Integrating molecular components into active synthetic cells is arising as a major goal of bioengineering and, by and large, multidisciplinary research. The encapsulation of cell-free transcription–translation systems into liposomes stands out of the current approaches because it enables programming synthetic cells with genes, as in real living cells, at the relevant biological scale and within the natural physical boundary. Although recapitulating certain biological functions in such minimal settings has been successful, serious barriers are still hard to overcome. In particular, implementing biological functions located at the lipid membrane remains one of the most challenging elements in bottom-up synthetic cell engineering. In this work, we review the current state-of-the-art of the membrane functions that have been achieved by cell-free expression, either on supported lipid bilayers, in the presence of membranes added to reactions or inside liposomes. We extend the considerations to the membrane functions sought in other types of artificial compartments.