Synthetic biology involves creating artificial replica that mimic the building blocks of living systems. It aims at recreating biological phenomena in the laboratory following a bottom-up approach. Today scientists routinely create micro-compartments, so called vesicles, such as liposomes and polymersomes. Their membranes can host biochemical processes and are made of self-assembled lipids or a particular type of polymers, called block copolymers, respectively. In a new study, researchers have developed a high-throughput method - based on an approach known as microfluidics - for creating stable vesicles of controlled size. The method is novel in that it works for both liposomes and polymersomes, without having to change the design of the microfluidic device or the combination of liquids. Julien Petit from the Max Planck Institute for Dynamics and Self-Organisation (MPIDS) in Göttingen, Germany and colleagues recently published these findings in EPJ E.
Typical applications in synthetic biology include the encapsulation of biological agents and creation of artificial cell membranes with a specific biochemical function, like the membrane processes that are part of cell metabolism. The authors anticipate that their method might also be applicable for the controlled fabrication of hybrid vesicles used in bio-targeting and drug-delivery. These are made of a mix of lipids and block copolymers, which combine the strengths of polymersomes-mechanical stability and chemical tenability - while retaining the biocompatibility and biofunctionality of the liposomes.
To create liposomes and polymersomes, the authors used a microfluidics platform made from the soft rubber PDMS, which is constituted of microchannels feeding two relevant substances into a single channel to combine them. To create their vesicles, Petit and colleagues produced water-in-oil-in-water (W/O/W) double-emulsions, where the lipid or block-copolymer molecules are dissolved in the oil phase. The liposomes and polymersomes are then formed as a result of a solvent-extraction process. Previous methods for polymersomes fabrication could not employ PDMS-based microfluidic platforms because of the powerful organic chemicals usually employed to dissolve the block-copolymers. In this study, the authors show that the size of the vesicles can be adjusted within a range of one order of magnitude by varying the flow rates of the different fluid phases - water and oil - during the fabrication of the double-emulsion.
Reference: Vesicles-on-a-chip: A Universal Microfluidic Platform for the Assembly of Liposomes and Polymersomes. J. Petit, I. Polenz, J.-C. Baret, S. Herminghaus, O. Bäumchen (2016), Eur. Phys. J. E 39: 59, DOI 10.1140/epje/i2016-16059-8