Synthetic biology meets liposome-based drug delivery

Synthetic biology is an emerging and rapidly expanding field of research focused on the assembly of novel biological systems with new functionalities tailored for different applications. Genetic circuits have been re-wired or constructed with elements from different organisms, and metabolic pathways have been engineered to endow cells with non-natural capabilities. One of the most exciting goals of synthetic biology is bringing solutions to biomedical challenges. Though this research area is still in its infancy, translational medicine is already witnessing the first steps towards the development of therapies based on synthetic biology.Cell-free synthetic biology (or in vitro synthetic biology), a branch of synthetic biology, makes use of cell-free gene expression systems to create biological networks that operate outside the chassis of a living cell. More than a decade ago, the convergence of synthetic biology, cell-free gene expression systems and liposome technology gave rise to the creation of artificial vesicle bioreactors that can synthesize genetically-encoded molecules. Though the primary motivation of these studies was the assembly of a semi-synthetic cell, the application of such technologies for different therapeutic purposes has been envisioned. Examples of this are the creation of antigen-producing liposomes as novel vaccination systems, the development of bioreactor liposomes suited for remotely controlled in-situ mRNA or protein production, and the assembly of a PCR-based nanofactory for gene delivery.Liposomes are the most successful drug delivery scaffolds ever developed with more than fifteen liposome-based drugs approved. Liposomes have long been investigated in the field of gene therapy as delivery vehicles for nucleic acids to overcome the barriers encountered by these molecules in vivo. In particular, the field of RNA interference-based drugs is very promising, with the first marketed formulation in 2018, and several others on their way.However, despite their long history of investigation, most of the structural and functional properties of the liposome-based drug delivery systems are inferred from bulk measurements. Therefore, the level of heterogeneity regarding, e.g. encapsulation efficiency, lipid composition, remains largely unknown within liposome preparations, which complicates the development of new formulations with improved therapeutic efficiency. Another important limitation is the observed membrane leakiness and premature drug release upon administration. Controlling the bio-distribution of a therapeutic drug is essential to minimize toxic side effects and enhance the efficiency of the treatment. To tackle this problem, the creation of targeting delivery systems with stimuli-responsive ability can improve the biodistribution profile of a drug and allow its delivery on demand.This work contributes to the convergence of the fields of synthetic biology, single-liposome biophysics and biomedicine, presenting different possible applications of vesicle bioreactors for the improvement of current RNA-based gene delivery systems