Tubulation of Supported Lipid Bilayer Membranes Induced by Photosensitized Lipid Oxidation

Abstract

We show that photosensitized phospholipid oxidation, initiated by the lipid-conjugated fluorophore TopFluor-PC, causes defects, namely, membrane tubes and vesicle-like structures, in supported lipid bilayers (SLBs). Lipid oxidation is detrimental to the integrity of the lipid molecules; when oxidized, they undergo a conformational expansion, which causes membrane tubes to protrude from the SLB. Lipid oxidation is verified by FT-IR spectroscopy, and area expansion is observed in Langmuir trough experiments. Upon growing to a critical length, the membrane tubes arising from SLBs rapidly undergo transition to vesicle-like structures. We find a correlation between the maximum tube length and the diameter of the resulting vesicle, suggesting the conservation of the surface area between these features. We use geometric modeling and the measured tube length and vesicle radius to calculate the tube radius; our calculated mean tube diameter of 243 nm is comparable to other groups' experimental findings. In the presence of fluid flow, membrane tubes can be extended to tens to hundreds of microns in length. SLBs composed of saturated lipids resist light-induced tubulation, and the inclusion of the lipophilic antioxidant α-tocopherol attenuates the tubulation process and increases the light intensity threshold for tubulation.

Fabrication of Lipid Nanotubules by Ultrasonic Drag Force

“…As illustrated in Video S5, the stretching speed in deionized water media reached 33 μm/s in the two-dimensional plane direction, as observed using a microscope. It was approximately ten times f a s t e r t h a n t h a t o f t h e e x i s t i n g m e t hods, 1,2,4,31,33,34,36,38,39,[45][46][47][48][49][50]55 where the highest stretching speed reported is merely 3.75 μm/s. 56 After being characterized by SEM, as shown in Figure 4e−g, it is observed that the microsized lipid vesicle (Figure 4e) as the traction head is used to drag out the nanosized hollow lipid nanotubule (Figure 4f).…”

“…Moreover, the stretching speed can reach 33 μm/s in the two-dimensional plane direction, and the length of the lipid nanotubules achieved millimeters. The phenomenon was not reported in the existing methods. ,,,,,,,,,− , …”

“…Some approaches of fabricating lipid nanotubules have been reported, ,,− which can be roughly categorized into two classes: self-assembly of lipid molecules and stretching lipid aggregates using external forces . Obviously, the self-assembly ,,, needs particular lipids and specific reaction conditions, which limits its further application.…”

Light‐Activated Synthetic Rotary Motors in Lipid Membranes Induce Shape Changes Through Membrane Expansion

“…Similar tubulations have been observed as a result of lipid peroxidation‐induced area expansion. [ 55 ] Notably, when SLBs with 10 mol.% bMM were observed under irradiation, the tubes and patches exhibited a signal for both the channels corresponding to the membrane and bMM . Lipowsky has explained in the context of supported bilayers why tubes growing from SLBs are energetically favorable as compared to vesicles.…”