Effects of inserting ultrashort carbon nanotubes into lipid bilayers on membrane morphology

Single-walled carbon nanotubes (CNTs) are carbon materials with unique thermal, optical, mechanical, and electrical properties, with hollow cylindrical structures of a few nanometers in diameter. CNTs cut to about 10 nm (Ultrashort CNTs, US-CNTs) can spontaneously insert into lipid bilayers. Therefore, applications have been proposed to combine CNTs with lipid bilayers to give the membranes the properties of CNTs. However, CNTs interact with membranes to induce morphological changes in the membranes, which may hinder these applications. In this study, to investigate the effects, US-CNTs are exposed to lipid bilayer vesicles (giant unilamellar vesicles, GUVs), which are used as a model for cell membranes, and the changes in membrane morphology with each US-CNT concentration were evaluated by fluorescence microscopy. As a result, GUVs show morphological changes upon exposure to US-CNTs, eventually transforming into a multiple vesicle-linked shape. This result suggests an increase in the area and asymmetry of the GUV membrane. Based on these results, we have proposed a hypothesis regarding the mechanism of morphological changes induced in the GUV membranes by US-CNTs exposure.