Microfluidic chip with pillar arrays for controlled production and observation of lipid membrane nanotubes

Lipid membrane nanotubes (NTs) are a widespread template forin vitrostudies of cellular processes happening at high membrane curvature. Traditionally NTs are manufactured one by one, using sophisticated membrane micromanipulations, while simplified methods for controlled batch production of NTs are in growing demand. Here we propose a lab-on-a-chip (LOC) approach to the simultaneous formation of multiple NTs with length and radius controlled by the chip design. The NTs form upon rolling silica microbeads covered by lipid lamellas over the pillars of a polymer micropillar array. The array's design and surface chemistry set the geometry of the resulting free-standing NTs. The integration of the array inside a microfluidic chamber further enables fast and turbulence-free addition of components, such as proteins, to multiple preformed NTs. This LOC approach to NT production is compatible with the use of high power objectives of a fluorescence microscope, making real-time quantification of the different modes of the protein activity in a single experiment possible.This work was partially supported by the Spanish Ministry of Science, Innovation, and Universities grants PGC2018-099971-B-I00, EUR2019-103830, RYC-2014-01419 and BIO2016-80417-P and the Basque Government grants IT1270-19 and IT1271-19. JMMG and MGH acknowledge the predoctoral fellowships from the University of the Basque Country (UPV/EHU). The authors are grateful for the technical support provided by SGIker (UPV/EHU and ERDF, EU) for the SEM experiments