Tailoring the appearance: what will synthetic cells look like?

Recently, the bottom-up assembly of a synthetic cell has emerged as a daring novel approach that can be expected to have major impact in generating fundamental insight in the organization and function of actual biological cells, as well as in stimulating a broad range of applications from drug delivery systems to chemical nanofactories. A crucial feature of any such synthetic cell is the architectural scaffold that defines its identity, compartmentalizes its inner content, and serves as a protective and selective barrier against its environment. Here we review a variety of potential scaffolds for building a synthetic cell. We categorize them as membranous structures (liposomes, fatty acid vesicles, polymersomes), emulsions (droplets and colloidosomes), and membrane-less coacervates. We discuss recent advances for each of them, and explore their salient features as candidates for designing synthetic cells.