Gene Expression Inside Liposomes: From Early Studies to Current Protocols.

Synthesizing proteins inside liposomes and other microcompartments is a well-established practice. However, the origin of this research is not from the distant past, dating back to 1999-2004, when the first successful attempts were published. Protein synthesis inside artificial compartments is now under strong expansion in the context of synthetic biology (in bottom-up approaches), and, in particular, it strongly contributes to the construction of artificial cell-like systems. These systems, often called "synthetic cells", can be used to model cellular processes, including membrane-centered ones. They are very innovative models that complement traditional studies and promise future applications. This review does not discuss all current directions in synthetic cell research; in particular, it does not include all kinds of artificial compartments. Instead, it is uniquely dedicated to the analysis of historical and technical developments of protein synthesis inside liposomes, highlighting a selected list of open questions. One of the goals is to note the importance of mastering liposome technology together with cell-free systems for the successful realization of this specific type of synthetic cell. With this aim, four currently employed protocols are compared and discussed, with a major emphasis on the droplet transfer method, which is attractive due to its simplicity and encapsulation efficiency.