Supramolecular interactions between β-cyclodextrin and hydrophobically end-capped poly(ethylene glycol)s: A quartz crystal microbalance study

Interfacial self-assembled behavior of pH/light-responsive host-guest alginate-based supra-amphiphiles for controlling emulsifying property

Soft emulsifiers with relatively suitable structural controllability are necessarily required for the preparation of multifunctional Pickering emulsions. Herein, a β-cyclodextrin-grafted alginate/azobenzene-functionalized dodecyl (Alg-β-CD/AzoC. 12) polymeric supra-amphiphile was designed based on the host-guest interfacial self-assembly. As compared with Alg-β-CD amphiphilic polymers, the interfacial tension of Alg-β-CD/AzoC12 supra-amphiphilic assemblies reduced from 29.57 mN/m to 0.18 mN/m, indicating the great amphiphilicity derived from Alg-β-CD/AzoC12 supra-amphiphilic assemblies. With the increase of pH, the interfacial microstructures transformed from flocculated structures, spherical structures into deformed structures. Especially, the spherical microstructures with the highest interfacial viscoelasticity and thickness demonstrated the highest emulsifying efficiency due to the steric hindrance mechanism. Moreover, the interfacial elastic modulus of adsorbed layers exhibited ~4 times of that upon the ultraviolet illumination. These results disclosed that the interfacial microstructures could be readily regulated by the tunable amphiphilicity of Alg-β-CD/AzoC12 assemblies, which would be useful for the applications of Pickering emulsions in numerous fields.

Cyclodextrin-Based Supramolecular Multilayer Assemblies for the Design of Biological Optical Sensors Using Tilted Fiber Bragg Gratings

In this work, we demonstrate the possibility to use optical fiber incorporating photowritten tilted fiber Bragg gratings (TFBG) as optical detection system for the real time monitoring of interfacial adsorption events and biological recognition. For this purpose, immobilization of cyclodextrin polymers onto the surface of optical fiber was envisioned through the layer-by-layer self-assembly method with the aim of developing sensing layers with well-defined host properties. To develop a biological sensor, amphiphilic dextran, acting as intermediate layer between the polyelectrolyte multilayer assembly and the biological probe, was immobilized though inclusion complex formation. The dextran layer exhibit a dual functionality: (i) it prevents non-specific proteins adsorption and (ii) it allows covalent immobilization of anti-bovine serum albumine through activation of the hydroxyl groups with 1,1’-carbonyl diimidazole. To verify the feasibility of our strategy, fluorescence microscopy was applied to evidence the effective inclusion of fluorescent macromolecular – flurorescein labelled dextran bearing adamantane as side-grafts – species within the cyclodextrin cavities present onto the optical fiber interface and at the last layer to prove the grafting of anti bovin serum albumin onto the amphiphilic dextran by a capture of fluorescein bovin serum albumin by the antibody layer. In a further step, it was demonstrated that the elaboration of the multilayer assembly can be monitored in real time using the TFBG sensor.

Molecular organization, structural orientation, and surface topography of monoacylated beta-cyclodextrins in monolayers at the air-aqueous interface

The surface behavior of monoacylated beta-cyclodextrins, with hydrocarbon chains of 16, 14, and 10 carbons, has been assessed by the measurement of the surface pressure, surface (dipole) potential, optical reflectivity, and surface topography in monolayers at the air-water interface. For all the derivatives studied, the intermolecular organization adopted along compression-decompression isotherms reveals a rich variety of packing states which imply profound reorganization of the hydrophobic and hydrophilic moieties of the beta-cyclodextrin derivatives in the film, depending on the lateral surface pressure. The intermolecular arrangements are consistent with the adoption of a different and defined orientation of the cyclic oligosaccharide unit, relative to the interfacial plane and the aqueous subphase. This is different from the behavior of the per-substituted derivatives, and none of the changes exhibited by the monosubstituted forms are consistent with the oligosaccharide ring remaining in a fixed orientation along the interface when the surface pressure is varied.