Alanine-Based Chiral Metallogels via Supramolecular Coordination Complex Platforms: Metallogelation Induced Chirality Transfer.

Chiral self-assemblies constantly attract great interest because of their potential to provide insight into biological systems and materials science. Herein we report on the efficient preparation of alanine-based chiral metallacycles, rhomboids 1D and 1L and hexagons 2D and 2L using a Pt(II) ← pyridyl directional bonding approach. The metallacycles are subsequently assembled into nanospheres at low concentration, that generate chiral metallogels at high concentration driven by hydrogen bonding, hydrophobic and π-π interactions. The gels consist of microscopic chiral nanofibers with well-defined helicity, as confirmed by circular dichroism (CD) and scanning (SEM) and transmission electron (TEM) microscopies. Given these results, we expect this technique will not only unlock interesting new approaches to understand homochirality in nature but also allow the design of versatile soft materials containing chiral supramolecular cores.

Single Nanochannel Platform for Detecting Chiral Drugs.

Chiral drugs play an essential role in medical and biochemical systems, and thus enantioselective analysis of chiral molecules has become a central focus in chemical, biological, medical, and pharmaceutical research. The design of chiral drug-detecting systems is a long-term and challenging task. Here we report the use of a modification-free nanochannel method for enantioselective recognition of S-naproxen from R-naproxen using N-acetyl-l-cysteine-capped gold nanoparticles as a chiral selector. The chiral discrimination is based on a drug-induced nanoparticle diastereoselective aggregation mechanism that blocks ion transport through the nanochannel. We demonstrated that high S-Npx selectivity in both water and biological samples can be achieved. This simple method has potential applications as a general platform for the detection of chiral molecules.

Chiral Selective Transport of Proteins by Cysteine-Enantiomer-Modified Nanopores.

Chirality is an intriguing and intrinsic feature of life and is highly associated with many significant biological processes. However, whether it influences the translocation behavior of proteins remains unclear. Herein, based on biomimetic strategies, we made chiral nanopores modified with cysteine enantiomers, and studied the chirality gating effects on protein transport. The results show that protein is preferentially transported through nanopores modified with l-cysteine because of chiral interaction, indicating chirality strongly influences protein transport process. This study presents a new method for better understanding the role of chirality in selective protein transport processes and provides a convenient approach for studying protein chiral separation and targeted treatments.

Temperature-Sensitive Artificial Channels through Pillar[5]arene-based Host-Guest Interactions.

In living systems, temperature-sensitive ion channels play a vital role in numerous cellular processes and can be controlled by biological ion channels in response to specific temperature stimuli. Facile pillar[5]arene-based host-guest interactions are introduced into a nanochannel pattern for constructing a temperature-sensitive artificial channel. Ion transport was switched from cations to anions by controlling the extent of the host bound to the guest with temperature stimuli. This efect is mainly due to the changing of the inner surface charge and wettability of the nanochannel during the process. This study paves a new way for better understanding the mechanism of temperature-sensitive properties and shows great promise for biomedical research.

Macroscopic Responsive Liquid Quantum Dots Constructed via Pillar[5]arene-Based Host-Guest Interactions.

Liquid quantum dots (QDs) have been used as a fluorescent films sensor. Constructing a macroscopic, responsive, liquid QD system for lysine (Lys) is a challenging task. To achieve a selective macroscopic response towards Lys, herein we present a new strategy for integrating host-guest chemistry into a liquid QD system. Water-soluble pillar[5]arene WP5 was designed and synthesized as a host. WP5 was introduced onto the surface of PEG1810-modified QDs by host-guest interactions to obtain liquid WP5-1810-QDs. The interaction between WP5 and Lys is stronger than that between WP5 and PEG-1810, causing WP5 to be released from the 1810-QDs surface in the presence of Lys, resulting in macroscopic fluorescence quenching. This smart material shows promise in amino acid sensing and separation.

Protein Adsorption Switch Constructed by a Pillar[5]arene-Based Host-Guest Interaction.

The interfacial properties of solid substrates are of importance for protein adsorption. Herein, we report a reversible protein adsorption switch based on the host-guest interaction of the butoxy pillar[5]arene and adipic acid. By the detector of the contact angle (CA), atomic force microscopy (AFM), and luminoscope on the silicon substrate, the intelligent protein switch exhibits excellent adsorptivity for BSA and switch performance by pH regulation.

Zn(2+) and EDTA Cooperative Switchable Nanofluidic Diode Based on Asymmetric Modification of Single Nanochannel.

Design and fabrication of smart switchable nanofluidic diodes remains a challenge in the life and materials sciences. Here, we present the first example of a novel Zn(2+)/EDTA switchable nanofluidic diode system based on the control of one-side of the modified hourglass-shaped nanochannel with salicylaldehyde Schiff base (SASB). The nanofluidic diode can be turned on in the response of Zn(2+) and turned off in response to EDTA solution with good reversibility and recyclability.

Dynamic Self-Assembly Adhesion of a Paraquat Droplet on a Pillar[5]arene Surface.

The adhesion of herbicide droplets on leaf surfaces plays an important role in the herbicide's adsorption by crops. How to control the adhesive binding which occurs through dynamic self-assembly between the macroscopic droplet and the surface is a challenging task. We introduce a host onto surfaces that controls the binding of guests in the paraquat droplets. The pillar[5]arene-functional surface showed the selective binding of paraquat droplets via the host-guest interaction. The work is promising for improving the efficiency of herbicides.

Calix[4]arene triazole-linked pyrene: click synthesis, assembly on graphene oxide, and highly sensitive carbaryl sensing in serum.

A fluorescent calix[4]arene triazole-linked pyrene (CP) was carefully designed and synthesized via click chemistry. The modification of CP with graphene oxide (GO) by a simple non-covalent interaction strategy is presented. Further inspection by electrochemical impedance spectroscopy reveals that the CP-GO could exhibit a very high supramolecular recognition for carbaryl, in particular in serum samples with a nanomolar concentration detection. Additionally, it is easy to directly observe macroscopic recognition by the contact angle, and expand practical applications.

Cu2+ ion responsive solvent-free quantum dots.

Three quantum dots (QDs) nanofluids modified with different lengths of PEG chainsare synthesized, and the property-structure relationship of QDs nanofluids is established, to achieve QDs nanofluids with tunable fluidic or optical performance. Notably, the proposed QDs nanofluids demonstrate a selective response towards Cu(2+)-based on both fluorescence and contact angle.

Design and fabrication of a biomimetic nanochannel for highly sensitive arginine response in serum samples.

Inspired from their biological counterparts, chemical modification of the interior surface of nanochannels with functional molecules may provide a highly efficient means to control ionic or molecular transport through nanochannels. Herein, we have designed and prepared a aldehyde calix[4]arene (C4AH), which was attached to the interior surface of a single nanochannel by using a click reaction, and that showed a high response for arginine (Arg). Furthermore, the nanofluidic sensing system has been challenged with complex matrices containing a high concentration of interfering sequences and serum. Based on this finding, we believe that the artificial nanochannel can be used for practical Arg-sensing devices, and be applied in a biological environment.

A photoresponsive wettability switch based on a dimethylamino calix[4]arene.

A photoreversible switch based on a photoresponsive host-guest system consisting of dimethylamino calix[4]arene L and 4-(phenylazo)benzoic acid (O) is reported. The host L exhibited selective binding and release of O on UV and visible irradiation at 450 and 365 nm, respectively. Moreover, the photoresponsive host-guest complex was applied as a photocontrolled wettability switch on a functional micro/nanostructured silicon surface, and is thus promising for applications in sensors and microfluidic devices.

A tryptophan responsive fluorescent and wettable dual-signal switch.

A new fluorescent dianthracene calix[4]arene (C4DA) was designed and synthesized via coupling the fluorescent anthracene units and calix[4]arene units. Then it was used to form self-assembled monolayers (C4DA-SAMs) by the simple click reaction to give the first fluorescent and wettable dual-signal switch for tryptophan (Trp) on a micro- and nano-structured silicon surface. The switch for Trp on the C4DA functional surface was confirmed by contact angle (CA) measurements and fluorescent spectroscopy (FL). Furthermore, the wettability-responsive C4DA functional interface can be re-used for six cycles. The responsive switch can potentially be applied in many fields including nanodevices and intelligent microfluidic switching.

Fabrication of layer-by-layer assembled biomimetic nanochannels for highly sensitive acetylcholine sensing.

Channel tunneling: We have prepared functional biomimetic nanochannels in polyethylene terephthalate (PET) polymer films (see illustration). We used p-sulfonatocalix[4]arene to modify the channel surface by flexible layer-by-layer electrostatic assembly. Using this method we were able to detect acetylcholine with high sensitivity.

Biomimetic ion nanochannels as a highly selective sequential sensor for zinc ions followed by phosphate anions.

A novel biomimetic ion-responsive multi-nanochannel system is constructed by covalently immobilizing a metal-chelating ligand, 2,2'-dipicolylamine (DPA), in polyporous nanochannels prepared in a polymeric membrane. The DPA-modified multi-nanochannels show specific recognition of zinc ions over other common metal ions, and the zinc-ion-chelated nanochannels can be used as secondary sensors for HPO4(2-) anions. The immobilized DPA molecules act as specific-receptor binding sites for zinc ions, which leads to the highly selective zinc-ion response through monitoring of ionic current signatures. The chelated zinc ions can be used as secondary recognition elements for the capture of HPO4(2-) anions, thereby fabricating a sensing nanodevice for HPO4(2-) anions. The success of the DPA immobilization and ion-responsive events is confirmed by measurement of the X-ray photoelectron spectroscopy (XPS), contact angle (CA), and current-voltage (I-V) characteristics of the systems. The proposed nanochannel sensing devices display remarkable specificity, high sensitivity, and wide dynamic range. In addition, control experiments performed in complex matrices suggest that this sensing system has great potential applications in chemical sensing, biotechnology, and many other fields.

Hg2+ wettability and fluorescence dual-signal responsive switch based on a cysteine complex of piperidine-calix[4]arene.

The recognition of the mercury(II) ion (Hg(2+)) is essential because of its extreme toxicity in the environment and food. Hence we reported a novel cysteine (Cys) complex of piperidine-calix[4]arene (L) as a convenient and effective dual-signal responsive switch for Hg(2+). This switch system exhibited excellent selectivity toward Hg(2+) by fluorescence (FL), (1)H NMR spectroscopy and the atomic force microscopy (AFM). More importantly, the Hg(2+)-responsive switch had an important and potential application by water contact angle (CA) on a functional micro-nano silicon surface, including intelligent microfluidic and laboratory-on-chip devices, controllable drug delivery, and self-cleaning surfaces.

Design of switchable wettability sensor for paraquat based on clicking calix[4]arene.

A calix[4]arene acetylene (C4AE)-modified gold surface is successfully constructed in situ via click chemistry. The functionalized surface is used for selective recognition of paraquat by a wettability switch. Impedance measurements showed that the surface also expresses recognition for paraquat with a high sensitivity of 10 pM. The recognition mode, based on host-guest inclusion, is studied by computational calculations and the possible mechanism is analyzed.

Supramolecular Biopharmaceutical Carriers Based on Host-Guest Interactions.

Traditional drugs have the disadvantages of poor permeability and low solubility, which makes the utilization of pesticides lower and brings many side effects. With the continuous development of supramolecular chemistry in recent years, it has also played an irreplaceable role in the field of pharmaceutical science. Supramolecular macrocycles, such as crown ethers, cyclodextrins, calixarenes, pillararenes and cucurbiturils, are potentially good candidates for drug carriers due to their biocompatibility, hydrophobic cavity and ease of derivatization. The encapsulation of drugs based on host-guest interaction has the advantage of being adjustable and reversible as well as improving the low availability of drugs. Here, the recent advances in methods and strategies for drug encapsulation and release based on supramolecular macrocycles with host-guest interactions have been systematically summarized, laying a bright foundation for the development of novel nanopesticide preparations in the future and pointing out future directions of novel biopesticide research.

Controlled release of drug molecules by pillararene-modified nanosystems.

Stimuli-responsive nanosystems have attracted the interest of researchers due to their intelligent function of controlled release regulated by a variety of external stimuli and have been applied in biomedical fields. Pillar[n]arenes with the advantages of a rigid structure, electron holes and easy functionalization are considered as excellent candidates for the construction of host-guest nanosystems. In recent years, many pillararene modified nanosystems have been reported in response to different stimuli. In this feature article, we summarize the advance of stimuli-responsive pillararene modified nanosystems for controlled release of drugs from the perspectives of decomposition release and gated release, focusing on the control principles of these nanosystems. We expect that this review can enlighten and guide investigators in the field of stimuli-responsive controlled release.

Urea-type ligand-modified CdSe quantum dots as a fluorescence "turn-on" sensor for CO3(2-) anions.

A new fluorescence "turn-on" nanosensor for carbonate determination was reported based on CdSe quantum dots (QDs) modified with thio ligands containing urea groups: N-(5-mercapto-1,3,4-thiadiazol-2-ylcarbamoyl)-2-(o-tolyloxy)acetamide (AASH-CdSe QDs). The AASH-CdSe QDs were prepared through a ligand exchange process and characterized by transmission electron microscopy (TEM), fluorescence spectroscopy, UV-vis spectroscopy and FT-IR spectroscopy. The synthesized AASH-CdSe QDs allowed a selective fluorescence "turn-on" response towards carbonate. Under optimal conditions, the relative fluorescence intensity increases linearly with carbonate concentration in the range 1 x 10(-7)-1 x 10(-4) M with a detection limit of 2.3 x 10(-8) M. A Langmuir-type binding model was highly effective in describing the carbonate concentration dependence of the luminescence intensity of the AASH-CdSe QDs. The possible mechanism was discussed.