Microfluidic characterization of biomimetic membrane mechanics with an on-chip micropipette

International audienceThe mechanic properties of cell membranes control many biological processes. The complexity of naturalmembranes is often dealt with by building synthetic vesicles (Giant Unilamellar Vesicles, GUVs), which can bethought as micron-sized minimal cells. Micropipette aspiration technique is the gold standard to characterizemembrane mechanics, but it involves manual, long and tedious experiments. Microfluidics is perfectly suited tohandle GUVs and permits in particular to conceive on-chip micropipettes for automated, systematic studies ofmembrane mechanical moduli. We developed a microfabrication process that enables obtaining the required 3-level channels including a micropipette in the intermediate level, with micrometric alignment, sufficiently lowadhesion and roughness. We extended the theoretical analysis of micropipette, valid for cylindrical geometriesthat microfabrication does not allow, to the on-chip geometry, by considering the deformation of a vesicle in asquare cross-section trap. We confirmed the validity of our approach thanks to systematic experiments performedon GUVs with well-characterized compositions: the obtained values of the membrane stretching modulusare in quantitative agreement with the literature. As a case study, we used our device to show that GUVschallenged with copolymer micelles, typically used for drug delivery, displayed a significantly decrease of themembrane stretching modulus, which could mediate internalization of these nanovectors. This study opens thepath to systematic studies of the influence of physico-chemical environment on the mechanics of cell membranes