Self-Assembly of Photoresponsive Molecular Amphiphiles in Aqueous Media

Photonic and Magnetic Dual-Responsive Molecularly Imprinted Sensor for Highly Specific Recognition of Enterovirus 71

The specific identification and detection of a virus are the critical factors to identify and control an epidemic situation. In this study, a novel photonic-magnetic responsive virus-molecularly imprinted photochemical sensor was constructed for recognition of enterovirus 71. As designed, the double-bond-modified magnetic metal organic framework and 4-(4'-acryloyloxyazo) benzoic acid were used as a magnetic carrier and light-responsive functional monomer, respectively. The structure of the recognition site of the virus-molecularly imprinted nanospheres can be photo-switched between two different structures to achieve rapid release and specific binding to the target virus. Additionally, the introduction of a magnetic core enables a rapid separation and recycling of imprinted particles. The device achieves a performance with high-specificity recognition (imprinting factor = 5.1) and an ultrahigh sensitivity with a detection limit of 9.5 × 10^-3 U/mL (3.9 fM). Moreover, it has good reproducibility and can be stored for as long as 6 months. Thus, the approach used in this work opens a new avenue for the construction of multiresponsive virus sensors.

Triggering a transient organo-gelation system in a chemically active solvent

A transient organo-gelation system with spatiotemporal dynamic properties is described. Here, the solvent actively controls a complex set of equilibria that underpin the dynamic assembly event. The observed metastability is due to the in situ formation of a secondary solvent, acting as an antagonist against the primary solvent of the organogel.

Influence of Polarity Change and Photophysical Effects on Photosurfactant-Driven Wetting

Photosurfactants have shown considerable promise for enabling stimuli-responsive control of the properties and motion of fluid interfaces. Recently, a number of photoswitch chemistries have emerged to tailor the photoresponsive properties of photosurfactants. However, systematic studies investigating how photoresponsive surfactant behavior depends on the photochemical and photophysical properties of the switch remain scarce. In this work, we develop synthetic schemes and surfactant designs to produce a well-controlled library of photosurfactants to comparatively assess the behavior of photoswitch chemistry on interfacial behavior. We employ photoinduced spreading of droplets at fluid interfaces as a model for such studies. We show that although photosurfactant response is largely guided by expected trends with changes in polarity of the photoswitch, interfacial behavior also depends nontrivially and sometimes counter-intuitively on the kinetics and mechanisms of photoswitching, particularly at the interface of two solvents, as well as on complex interactions with other surfactants. Understanding these complexities enables the design of new photosurfactant systems and their optimization toward responsive functions including triggered spreading, dewetting, and destabilization of droplets on solid and fluid surfaces.

Self-Assembly of a Triazolylferrocenyl Dendrimer in Water Yields Nontraditional Intrinsic Green Fluorescent Vesosomes for Nanotheranostic Applications

The promising field of nanomedicine stimulates a continuous search for multifunctional nanotheranostic systems for imaging and drug delivery. Herein, we demonstrate that application of supramolecular chemistry's concepts in dendritic assemblies can enable the formation of advanced dendrimer-based nanotheranostic devices. A dendrimer bearing 81 triazolylferrocenyl terminal groups adopts a more compact shell-like structure in polar solvents with the ferrocenyl peripheral groups backfolding toward the hydrophobic dendrimer interior, while exposing the more polar triazole moieties as the dendritic shell. Akin to lipids, the compact dendritic structure self-assembles into uniform nanovesicles that in turn self-assemble into larger vesosomes in water. The vesosomes emit green nontraditional intrinsic fluorescence (NTIL), which is an emerging property as there are no classical fluorophores in the dendritic macromolecular structure. This work confirms the hypothesis that the NTIL emission is greatly enhanced by rigidification of the supramolecular assemblies containing heteroatomic subluminophores (HASLs) and by the presence of electron rich functional groups on the periphery of dendrimers. This work is the first one detecting NTIL in ferrocenyl-terminated dendrimers. Moreover, the vesosomes are stable in biological medium, are uptaken by cells, and show cytotoxic activity against cancer cells. Accordingly, the self-organization of these dendrimers into tertiary structures promotes the emergence of new properties enabling the same component, in this case, ferrocenyl group, to function as both antitumoral drug and fluorophore.

Self-Assembly of Photoresponsive Molecular Amphiphiles in Aqueous Media

Amphiphilic molecules, comprising hydrophobic and hydrophilic moieties and the intrinsic propensity to self-assemble in aqueous environment, sustain a fascinating spectrum of structures and functions ranging from biological membranes to ordinary soap. Facing the challenge to design responsive, adaptive, and out-of-equilibrium systems in water, the incorporation of photoresponsive motifs in amphiphilic molecular structures offers ample opportunity to design supramolecular systems that enables functional responses in water in a non-invasive way using light. Here, we discuss the design of photoresponsive molecular amphiphiles, their self-assembled structures in aqueous media and at air-water interfaces, and various approaches to arrive at adaptive and dynamic functions in isotropic and anisotropic systems, including motion at the air-water interface, foam formation, reversible nanoscale assembly, and artificial muscle function. Controlling the delicate interplay of structural design, self-assembling conditions and external stimuli, these responsive amphiphiles open several avenues towards application such as soft adaptive materials, controlled delivery or soft actuators, bridging a gap between artificial and natural dynamic systems.

Hydrogen-bonding mediated self-assembly of amphiphilic ABA triblock copolymers into well-defined giant vesicles

A straightforward and efficient access towards the generation of well-defined giant vesicles (∼3 μm in diameters), featured by Hydrogen-bonded DAP–DAP dimerization, and the amphiphilic interactions is reported.

Synthesis and characterization of photochromic triethylene glycol-containing spiropyrans and their assembly in solution

A series of photochromic triethylene glycol (TEG)-containing spiropyrans (SPs) has been synthesized, and systematic and controlled formation of their self-assembled functional materials has been achieved.

Adsorption of Photoresponsive Surfactants at Solid-Liquid Interfaces

We report on the adsorption kinetics of azobenzene-containing surfactants on solid surfaces of different hydrophobicity. The understanding of this processes is of great importance for many interfacial phenomena that can be actuated and triggered by light, since the surfactant molecules contain a photoresponsive azobenzene group in their hydrophobic tail. Three surfactant types are studied, differing in the spacer connecting the headgroup and the azobenzene unit by between 6 and 10 CH₂ groups. Under irradiation with light of a suitable wavelength, the azobenzene undergoes reversible photoisomerization between two states, a nonpolar trans-state and a highly polar cis-state. Consequently, the surfactant molecule changes its hydrophobicity and thus affinity to a surface depending on the photoisomerization state of the azobenzene. The adsorption behavior on hydrophilic (glass) and hydrophobic (TeflonAF) surfaces is analyzed using quartz crystal microbalance with dissipation (QCM-D) and ζ-potential measurements. At equilibrium, the adsorbed surfactant amount is almost twice as large on glass compared to TeflonAF for both isomers. The adsorption rate for the trans-isomers on both surfaces is similar, but the desorption rate of the trans-isomers is faster at the glass-water interface than at the Teflon-water interface. This result demonstrates that the trans-isomers have higher affinity for the glass surface, so the trans-to-cis ratios on glass and TeflonAF are 80/1 and 2/1, respectively, with similar trends for all three surfactant types.