Characteristic curved structure derived from collagen-containing tubular giant vesicles under static magnetic field

Identifying and Manipulating Giant Vesicles: Review of Recent Approaches

Giant vesicles (GVs) are closed bilayer membranes that primarily comprise amphiphiles with diameters of more than 1 μm. Compared with regular vesicles (several tens of nanometers in size), GVs are of greater scientific interest as model cell membranes and protocells because of their structure and size, which are similar to those of biological systems. Biopolymers and nano-/microparticles can be encapsulated in GVs at high concentrations, and their application as artificial cell bodies has piqued interest. It is essential to develop methods for investigating and manipulating the properties of GVs toward engineering applications. In this review, we discuss current improvements in microscopy, micromanipulation, and microfabrication technologies for progress in GV identification and engineering tools. Combined with the advancement of GV preparation technologies, these technological advancements can aid the development of artificial cell systems such as alternative tissues and GV-based chemical signal processing systems.

Light reflection control in biogenic micro-mirror by diamagnetic orientation

As has become known, most materials, such as proteins and DNA, show orientation under strong magnetic fields. However, the critical threshold for the magnetic field of the magnetomechanical phenomena is still unknown. We demonstrate that a thin micro-mirror from a fish scale with high reflectivity exhibits a distinct magnetic response at 100 mT. A dramatic event under a magnetic field is the decrease of light scattering from guanine crystals as well as rapid rotation against the applied magnetic field. Enhancement of light scattering intensity is also observed when the three vectors of light incidence, magnetic field, and observation are orthogonally directed. The results indicate that biogenic guanine crystals have a large diamagnetic anisotropy along the surface parallel and normal directions. The micrometer to submicrometer scale of thin biogenic plates can act as a noninvasively, magnetically controlled micro-mirror for light irradiation control in the micrometer-scale region.

Multitude of morphological dynamics of giant multilamellar vesicles in regulated nonequilibrium environments

Lipid giant vesicles (GVs) exhibit biologically relevant morphological dynamics such as growth and division under certain conditions without any sophisticated molecular machineries employed by the current organisms. Nonequilibrium conditions are essential for the emergence of dynamic behaviors, which are normally generated by the addition of stimulating materials or by the change of some physical conditions. Therefore, an experimental method that allows flexible control of external conditions is desirable. Here we report a new and simple perfusion device for light microscopy observation that simultaneously realizes such control and tracking of individual phospholipid GVs for the long-term. We apply this device to the study of the morphological dynamics of POPC-based giant multilamellar vesicles (GMVs) under a monotonic and gradual increase of surfactant concentration; thereby we reveal the existence of multiple pathways in the slow solubilization processes, whose frequencies depend on the compositions of GMVs. This perfusion device would offer an unprecedented control of external conditions in the studies of GVs and might help us characterize the physicochemical origins of rich morphological dynamics of living cells.

Anisotropic surface tension of buckled fluid membranes

Thin solid sheets and fluid membranes exhibit buckling under lateral compression. Here it is revealed that buckled fluid membranes have anisotropic mechanical surface tension contrary to solid sheets. Surprisingly, the surface tension perpendicular to the buckling direction shows stronger dependence on the projected area than that parallel to it. Our theoretical predictions are supported by numerical simulations of a meshless membrane model. This anisotropic tension can be used to measure the membrane bending rigidity. It is also found that phase synchronization occurs between multilayered buckled membranes.