Microfluidic characterization of biomimetic membrane mechanics with an on-chip micropipette
Résumé
The mechanic properties of cell membranes control many biological processes. The complexity of natural
membranes is often dealt with by building synthetic vesicles (Giant Unilamellar Vesicles, GUVs), which can be
thought as micron-sized minimal cells. Micropipette aspiration technique is the gold standard to characterize
membrane mechanics, but it involves manual, long and tedious experiments. Microfluidics is perfectly suited to
handle GUVs and permits in particular to conceive on-chip micropipettes for automated, systematic studies of
membrane 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 low
adhesion and roughness. We extended the theoretical analysis of micropipette, valid for cylindrical geometries
that microfabrication does not allow, to the on-chip geometry, by considering the deformation of a vesicle in a
square cross-section trap. We confirmed the validity of our approach thanks to systematic experiments performed
on GUVs with well-characterized compositions: the obtained values of the membrane stretching modulus
are in quantitative agreement with the literature. As a case study, we used our device to show that GUVs
challenged with copolymer micelles, typically used for drug delivery, displayed a significantly decrease of the
membrane stretching modulus, which could mediate internalization of these nanovectors. This study opens the
path to systematic studies of the influence of physico-chemical environment on the mechanics of cell membranes.
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