Contactless Stimulation and Control of Biomimetic Nanotubes by Calcium Ion Gradients

Abstract

Membrane tubular structures are important communication pathways between cells and cellular compartments. Studying these structures in their native environment is challenging, due to the complexity of membranes and varying chemical conditions within and outside of the cells. This work demonstrates that a calcium ion gradient, applied to a synthetic lipid nanotube, triggers lipid flow directed toward the application site, resulting in the formation of a bulge aggregate. This bulge can be translated in a contactless manner by moving a calcium ion source along the lipid nanotube. Furthermore, entrapment of polystyrene nanobeads within the bulge does not tamper the bulge movement and allows transporting of the nanoparticle cargo along the lipid nanotube. In addition to the synthetic lipid nanotubes, the response of cell plasma membrane tethers to local calcium ion stimulation is investigated. The directed membrane transport in these tethers is observed, but with slower kinetics in comparison to the synthetic lipid nanotubes. The findings of this work demonstrate a novel and contactless mode of transport in lipid nanotubes, guided by local exposure to calcium ions. The observed lipid nanotube behavior can advance the current understanding of the cell membrane tubular structures, which are constantly reshaped during dynamic cellular processes.

Asymmetrical Calcium Ions Induced Stress and Remodeling in Lipid Bilayer Membranes

“…This kind of remodeling can only be generated by an asymmetric effect in the two leaflets of membranes, which may be related to membrane budding and fusion [49,50], as well as generation of interconnected vesicles [51]. For example, dynamic membrane remodeling may be achieved by the interplay between lipids and Ca 2+ to initiate the formation of tubules [52][53][54]. In contrast, when the impact of Ca 2+ is uniform on the membrane surface and Ca 2+ ions are added to the outside, the vesicle tends to remain spherical, and stomatocyte shapes can be metastable under a large spontaneous curvature.…”

Ligand-binding assay based on microfluidic chemotaxis of porphyrin receptors

“…46 Additionally, systems with many favourable specic solute recognitions or nonspecic solvation would be expected to undergo large shis. 4,9,49 Fig. 8…”

Versatile Phospholipid Assemblies for Functional Synthetic Cells and Artificial Tissues

“…Their fabrication methods mainly categorize into two types, that is, self‐assembly of phospholipid molecules, [ 57,59,118,119 ] and external stimuli induced tube formation. [ 123–142 ] The self‐assembly method requires special phospholipid molecules, DC (8,9) PC (Table 1) or the mixture of DC (8,9) PC and DNPC [ 59 ] (Table 1). The typical procedure is to dissolve DC (8,9) PC in an ethanol solution (50–70%) and decrease the temperature from 40 °C to room temperature.…”

“…[ 130 ] Micromanipulation technique is able to prepare vesicle–nanotube networks [ 131 ] which can be used to study membrane proteins migration via the nanotube connecting two vesicles, [ 132,133 ] and mimic the cargo transfer between biological cells. [ 23,123,124 ] The hypertonic state by increasing the external concentration of Ca 2+ , [ 134,135 ] or sugar [ 11,76,125 ] can induce inwards tubular protrusion from GUVs.…”