A Visible-Light Regulated ATP Transport in Retinal-Modified Pillar[6]arene Layer-by-Layer Self-Assembled Sub-Nanochannel.

Natural light-responsive rhodopsins play a critical role in visual conversion, signal transduction, energy transmission, etc., which has aroused extensive interest in the past decade. Inspired by these gorgeous works of living beings, scientists have constructed various biomimetic light-responsive nanochannels to mimic the behaviors of rhodopsins. However, it is still challenging to build stimuli-responsive sub-nanochannels only regulated by visible light as the rhodopsins are always at the sub-nanometer level and regulated by visible light. Pillar[6]arenes have an open cavity of 6.7 Å, which can selectively recognize small organic molecules. They can be connected to ions of ammonium or carboxylate groups on the rims. Therefore, we designed and synthesized the amino and carboxyl-derived side chains of pillar[6]arenes with opposite charges. The sub-nanochannels were constructed through the electrostatic interaction of layer-by-layer self-assembled amino and carboxyl-derived pillar[6]arenes. Then, the natural chromophore of the retinal with visible light-responsive performance was modified on the upper edge of the sub-nanochannel to realize the visible light switched on and off. Finally, we successfully constructed a visible light-responsive sub-nanochannel, providing a novel method for regulating the selective transport of energy-donating molecules of ATP.

Guest-Induced Planar-Chiral Pillar[5]arene Surface for Selectively Adsorbing Protein Based on Host-Guest Chemistry.

In living systems, the adsorption of a protein on biointerfaces is a universal phenomenon, such as the specific binding of an antibody and antigen, which plays an important role in body growth and life maintenance. The exploration of a protein-selective adsorption on the biointerface is of great significance for understanding the life process and treatment in vitro. Herein, on the basis of biomimetic strategies, we fabricated a planar-chiral NH2-pillar[5]arene modified silicon surface (pR-/pS-NP5 surfaces) for a highly enantioselective adsorption of protein by taking advantage of the guest-induced planar chirality of pillar[5]arenes. Results from practical experiments and theoretical calculations show that the pR-NP5 surface possesses a high adsorption capacity and chiral selectivity for bovine serum albumin (BSA). Moreover, it was identified that the guest-induced chiral effect the generation and amplification of planar chirality, which was much beneficial for enhancing the interaction between planar-chiral pillar[5]arene host and BSA. The binding capacity of pR-NP5 and BSA is stronger than that of pS-NP5, thus promoting the chiral selective adsorption of BSA. This work affords a deeper understanding of the chiral influence of protein adsorption on biointerfaces and meanwhile provides a new perspective for chiral-sensing applications.

Efficient Chiral Nanosenor Based on Tip-Modified Nanochannels.

Enantiomers of various drug molecules have a specific effect on living organisms. Accordingly, developing a sample method for the efficient and rapid recognition of chiral drug enantiomers is of great industrial value and physiological significance. Here, inspired by the structure of ion channels in living organisms, we developed a chiral nanosensor based on an artificial tip-modified nanochannel system that allows efficient selective recognition of chiral drugs. In this system, l-alanine-pillar[5]arenes as selective receptors were introduced on the tip side of conical nanochannels to form an enantioselective "gate". The selective coefficient of our system toward R-propranolol is 4.96, which is higher than the traditional fully modified nanochannels in this work.

Targeted and Long-Term Fluorescence Imaging of Plant Cytomembranes Using Main-Chain Charged Polyelectrolytes with Aggregation-Induced Emission.

Fluorescent polyelectrolytes have attracted tremendous attention due to their unique properties and wide applications. However, current research objects of fluorescent polyelectrolytes mainly focus on side-chain charged polyelectrolytes, and the applications of polyelectrolytes in plant cytomembrane imaging with long time and high specificity still remain challenging. Herein, long-time and targeted fluorescence imaging of plant cytomembranes was achieved for the first time using main-chain charged polyelectrolytes (MCCPs) with aggregation-induced emission (AIE). A series of MCCPs were designed and synthesized, among which the red-emissive and AIE-active MCCP with a triphenylamine linker and a cyano group around the cationic ring-fused heterocyclic core showed the best fluorescence imaging performance of plant cells. Unlike other MCCPs and its neutral form of polymer, this cyano-substituted conjugated polyelectrolyte can specifically target the cytomembrane of plant cells within a short staining time with many advantages, including wash-free staining, high photostability and imaging integrity, excellent durability (at least 12 h), and low biotoxicity. In addition to onion epidermal cells, this AIE fluorescence probe also shows good imaging capabilities for other kinds of plant cells such as Glycine max and Vigna radiata. Such an AIE-active MCCP-based imaging system provides an effective design strategy to develop fluorescence probes with high specificity and long-term imaging ability toward plant plasma membranes.

Synergistically Boosting the Circularly Polarized Luminescence of Functionalized Pillar[5]arenes by Polymerization and Aggregation.

Supramolecular polymers based on chiral macrocycles have attracted increasing attention in the field of circularly polarized luminescence (CPL) owing to their unique properties. However, the construction of macrocyclic supramolecular polymers with highly efficient CPL properties in aggregate states still remains challenging. Herein, w e constructed a class of macrocycle-based coordination polymers by combining the planar chiral properties of pillar[5]arene with the excellent fluorescence properties of aggregation-induced emission luminogens. The formation of polymers enhances both the fluorescence and chiral properties, resulting in chiral supramolecular polymers with remarkable CPL properties. Increasing the aggregation degree of the polymers can further improve their CPL properties, as evidenced by a 21-fold increase in the dissymmetry factor and an over 25-fold increase in the fluorescence quantum yield in the aggregate state compared to the solution state. Such a synergistic effect of polymerization- and aggregation-enhanced CPL can be explained by the restriction of intramolecular motions and aggregation-induced conformation confinement. This work provides a promising method for developing highly efficient CPL supramolecular polymers.

Promoting the Spreading of Droplets on a Superhydrophobic Surface by Supramolecular Amphiphilic Complex-Based Host-Guest Chemistry.

The spreading of pesticide droplets on the surface of superhydrophobic plants is an important process, which can prevent the inadequate retention such as bouncing, splashing, and drifting, thereby improving the efficiency of pesticide utilization and reducing soil and groundwater pollution. Herein, we report an approach to fabricate a supramolecular amphiphilic system that significantly contributes to this issue. The hydrophilic amino-pillar[5]arene was synthesized, which could form vesicles with the hydrophobic long-chain guest. This host-guest complex decreased the surface tension, which greatly promotes the spreading of droplets. This study provides a new strategy for prolonging pesticide retention and reducing pesticide loss.

A layer-by-layer assembled D/L-arginine-calix[4]arene-Si-surface for macroscopic enantio-selective discrimination of (R)/(S)-ibuprofen.

Chiral arginine was introduced by layer-by-layer assembly onto a calix[4]arene-diacid modified silica surface to control the adsorption of different kinds of ibuprofen droplets. The droplet of (S)-ibuprofen slid off rapidly, whereas the droplet of (R)-ibuprofen absorbed on the modified surface.

Phenethylamine@Pillar[5]arene Biointerface for Highly Enantioselective Adsorption of Protein.

In the life system, the biointerface plays an important role in cell adsorption, platelet adsorption and activation. Therefore, the study of protein adsorption on the biointerface is of great significance for understanding life phenomena and treatment in vitro. In this paper, a chiral biointerface was constructed by the virtue of host-guest interaction between a water-soluble pillar[5]arene (WP5) and phenethylamine (PEA) over a gold surface for adsorption of lysozyme proteins. From the experimental results it was identified that the host-guest biointerface has a high adsorption capacity and strong chiral selectivity. Furthermotre, it was identified that the host-guest interaction plays the decisive role in the enhancement of chirality of the interface, which was much beneficial for increasing protein adsorption and amplifying the capacity of chiral discrimination. Therefore, this work provides a new idea for the construction of biointerface materials with high protein adsorption capacity and high chiral selectivity through supramolecular interaction, which will have potential applications in the fields of biosensors, biocatalysts, biomaterials.

Enantioselective Dynamic Self-Assembly of Histidine Droplets on Pillar[5]arene-Modified Interfaces.

The self-assembly of macroscopic droplets on interfaces has attracted much attention and shown promising potential in the field of materials as a sensing or delivery system. Herein, we reported a new strategy to construct a d-tartaric acid-functionalized pillar[5]arene (d-TP5) interface for macroscopic differentiation of histidine enantiomers. At the molecular level, it has been proved that d-TP5 has the ability to distinguish between l-Histidine and d-Histidine ( KL/ KD = 4.6). Furthermore, a functional d-TP5 surface was constructed by a click reaction and characterized by contact angle measurements and attenuated total reflection-Fourier-transform infrared spectroscopy and X-ray photoelectron spectroscopy analyses. The d-TP5 surface exhibited the selective dynamic adhesion of l-His droplets on the tilted interface. It means that a d-TP5 surface can distinguish histidine enantiomers at a macrolevel. The amount of d/l-His absorbed by a d-TP5 surface and the morphology of His particles formed by removing the solvent have been investigated to prove that the self-assembly of His occurs on the d-TP5 surface. The possible mechanism has been discussed from host-guest interaction and chiral recognition. The proposed chiral material displays rapidly remarkable selectivity and is convenient to be utilized, which should be suitable for comprehending chiral recognition processing and applied to chiral recognition detection of histidine in a living body.

A Chirality/Light Dual-Responsive Calixarene-Functionalized Gold Surface for the Separation of Naproxen Enantiomers.

Chiral and photo-responsive calix[4]arene (trans CAC4) host system that can be adsorbed onto gold surfaces was rationally designed and produced in quantitative yields. Chiral recognition through strong host-guest interaction between trans CAC4 and (R)-naproxen was confirmed by fluorescence titration and 1 H NMR analysis. Functionalization of the gold surface with trans CAC4 was demonstrated by increased contact angle and XPS measurement. Photoswitching by trans-cis isomerization of CAC4 and CAC4-modified gold surfaces was confirmed by UV-vis spectroscopy and contact angle experiments. Trans CAC4-modified gold surfaces showed selective adsorption towards (R)-naproxen, while cis CAC4-modified gold surfaces did not show any distinctive interaction with (R)/(S)-naproxen. Langmuir isothermal plots and LSCM studies proved quantitative adsorption of (R)-naproxen by the trans CAC4-modified surface. This study demonstrated chiral recognition of a drug system by visual macroscopic changes, which may be used as a convenient methodology to separate bioactive enantiomers.