Sugar‐Decorated Sugar Vesicles: Lectin–Carbohydrate Recognition at the Surface of Cyclodextrin Vesicles

An artificial glycocalix self‐assembles when unilamellar bilayer vesicles of amphiphilic β‐cyclodextrins are decorated with maltose and lactose by host–guest interactions. To this end, maltose and lactose were conjugated with adamantane through a tetra(ethyleneglycol) spacer. Both carbohydrate–adamantane conjugates strongly bind to β‐cyclodextrin (K_a≈4×10⁴ M ^?1). The maltose‐decorated vesicles readily agglutinate (aggregate) in the presence of the lectin concanavalin A, whereas the lactose‐decorated vesicles agglutinate in the presence of peanut agglutinin. The orthogonal multivalent interaction in the ternary system of host vesicles, guest carbohydrates, and lectins was investigated by using isothermal titration calorimetry, dynamic light scattering, UV/Vis spectroscopy, and cryogenic transmission electron microscopy. It was shown that agglutination is reversible, and the noncovalent interaction can be suppressed and eliminated by the addition of competitive inhibitors, such as D ‐glucose or β‐cyclodextrin. Also, it was shown that agglutination depends on the surface coverage of carbohydrates on the vesicles.     

Self‐Assembled Vesicles with Functionalized Membranes

Biological membranes play a key role for the function of living organisms. Thus, many artificial systems have been designed to mimic natural cell membranes and their functions. A useful concept for the preparation of functional membranes is the embedding of synthetic amphiphiles into vesicular bilayers. The dynamic nature of such noncovalent assemblies allows the rapid and simple development of bio‐inspired responsive nanomaterials, which find applications in molecular recognition, sensing or catalysis. However, the complexity that can be achieved in artificial functionalized membranes is still rather limited and the control of their dynamic properties and the analysis of membrane structures down to the molecular level remain challenging.     

Thermoresponsive Organic–Inorganic Hybrid Large‐Compound Vesicles

Herein, gelated thermoresponsive large‐compound vesicles (LCVs) are reported for the first time. The LCVs are prepared by self‐assembly of poly(ethylene oxide)‐block‐poly[N‐isopropylacrylamide‐random‐3‐(trimethoxysilyl)propyl methacrylate] [PEO‐b‐P(NIPAM‐r‐TMPM)] in DMF‐water mixture. Then, sol‐gel reaction of the reactive PTMPM block is performed to stabilize the LCVs. LCVs with higher cross‐linking density keep almost the same size under different temperatures while LCVs with lower cross‐linking density display obviously thermoresponsive size transition between 22 and 36 °C. The gelated LCVs exhibit enhanced permeability with temperature elevation and their permeabilities at different temperatures all elevate with increasing the cross‐linking density.

     

Barcoding Biological Reactions with DNA‐Functionalized Vesicles

Targeted vesicle fusion is a promising approach to selectively control interactions between vesicle compartments and would enable the initiation of biological reactions in complex aqueous environments. Here, we explore how two features of vesicle membranes, DNA tethers and phase‐segregated membranes, promote fusion between specific vesicle populations. Membrane phase‐segregation provides an energetic driver for membrane fusion that increases the efficiency of DNA‐mediated fusion events. The orthogonality provided by DNA tethers allows us to direct fusion and delivery of DNA cargo to specific vesicle populations. Vesicle fusion between DNA‐tethered vesicles can be used to initiate in vitro protein expression to produce model soluble and membrane proteins. Engineering orthogonal fusion events between DNA‐tethered vesicles provides a new strategy to control the spatiotemporal dynamics of cell‐free reactions, expanding opportunities to engineer artificial cellular systems.     

Gas‐Constructed Vesicles with Gas‐Moldable Membrane Architectures

Integrating gas as a main building block into nanomaterial construction is a challenging mission that remains elusive. Herein, we report a gas‐constructed vesicular system formed by CO₂ gas and frustrated Lewis pairs (FLPs). Two molecular triads bearing three bulky borane and phosphine groups are designed as trivalent disc‐like FLP monomers. CO₂, as a gas cross‐linker, can drive the two‐dimensional polymerization of these two FLP monomers, leading to the generation of planar FLP networks that further transform into a thermodynamically favored membranous vesicle structure. Gas‐guided vesicle formation is also applicable to other inert but FLP‐activatable gases. Different gas linkages can form vesicles with distinct architectures, sizes, and morphologies. We envisage that this study would suggest a new concept that exploits gases to fabricate tunable nanomaterials.     

Hydrogen Bonding‐Induced Transformation of Network Aggregates into Vesicles ‐ A Potential Method for the Preparation of Composite Vesicles

While network‐like assemblies are formed by amphiphilic polyphosphazenes with poly(N‐isopropylacrylamide) and ethyl tryptophan as side groups in aqueous solution, a significant morphology transformation is observed when small molecules that exhibit hydrogen‐bonding interactions with amphiphilic copolymers are introduced during the preparation of polymeric assemblies through a dialysis procedure. Depending on copolymer composition and the content of small molecules introduced, aggregates ranging from general vesicles, high‐genus vesicles, to well‐defined nanospheres can be prepared successfully as clearly evidenced by TEM observation, which suggests this procedure should be a novel approach to prepare composite vesicles.

     

UV‐Responsive Supramolecular Vesicles with Double Hydrophobic Chains

In order to improve the stability of polymeric vesicles, supramolecular vesicles are developed via self‐assembly of the inclusion of γ‐cyclodextrin (γ‐CD) and 1‐pyrenemethyl palmitate (Py‐pal). The inclusion has one hydrophilic head and double hydrophobic tails, which looks like the phospholipid. From the transmission electron microscopy (TEM) image, it can be observed that the average diameter of supramolecular vesicles is approximately 55 nm and there is a huge cavity in supramolecular vesicles. Due to the photo‐breakable ester of Py‐pal, supramolecular vesicles are broken under UV irradiation. Supramolecular vesicles are used as UV‐responsive drug carriers to release the hydrophilic drug such as doxorubicin hydrochloride (DOX•HCl).

     

Reversibly Triggered Protein–Ligand Assemblies in Giant Vesicles

External small‐molecule triggers were used to reversibly control dynamic protein–ligand interactions in giant vesicles. An alcohol dehydrogenase was employed to increase or decrease the interior pH upon conversion of two different small‐molecule substrates, thereby modulating the pH‐sensitive interaction between a Ni‐NTA ligand on the vesicle membrane and an oligohistidine‐tagged protein in the lumen. By alternating the small‐molecule substrates the interaction could be reversed.     

Sterically Stabilized Vesicles

After significant developments in liquid crystal and polymer research, scientists became interested in lyotropic systems containing polymers. These studies investigated, for instance, phase behavior and stability characteristics of suspensions of colloidal particles containing water-soluble or surface-adsorbed polymers or block copolymers. The most frequently studied were micelles, latex prticles, and lipid vesicles (liposomes). Liposomes aggregate and fuse in the presence of hydrophilic polymers but their properties were difficult to explain when block copolymers were adsorbed or surfactants with larger polymeric polar heads were inserted into the liposome membrane, because such systems are inherently ill defined. Liposomes containing diacyl surfactants with covalently linked, longer polymer chains display many new properties with very important consequences for both basic and applied research. They stimulate fundamental studies on phase behavior and polymer conformation, scaling laws, colloidal and surface properties, and cell function: applications deal predominantly with liposomes as drug delivery systems. While in basic research theory is currently more advanced than experiment, in medical applications theoretical understanding lags behind experimental achievements. It was discovered only relatively late that liposomes with an appropriate polymer coating are significantly more stable in a biological milieu, a necessary condition for their utility as drug carriers. In particular in medical applications, this practice has rejuvenated the field of anticancer therapy and targeted drug deliviery. All these advances were made possible by an effective and synergistic overlap of many different disciplines.     

Crosslinkable Vesicles Self‐Assembled by Amphiphilic Hyperbranched Polyester

Summary: Amphiphilic hyperbranched polyester (H20‐AM) with methacrylate end groups was synthesized based on hyperbranched aliphatic polyester (Boltorn™ H20). Narrow‐dispersed crosslinkable vesicles were obtained by dissolving H20‐AM in water, and characterized by laser light scattering and TEM. The hollow structural vesicle is composed of around 350 H20‐AM molecules, having a radius of around 40 nm and of 1.9 × 10⁶ g · mL⁻¹. The vesicles were fixed by crosslinking of methacrylate groups to form shape‐persistent structures.

TEM images of the crosslinked vesicles at lower magnification.