Reversible Control of Gene Expression by Guest-Modified Adenosines in a Cell-Free System via Host-Guest Interaction

Gene expression technology has become an indispensable tool for elucidating biological processes and developing biotechnology. Cell-free gene expression (CFE) systems offer a fundamental platform for gene expression-based technology, in which the reversible and programmable control of transcription can expand its use in synthetic biology and medicine. This study shows that CFE can be controlled via the host-guest interaction of cucurbit[7]uril (CB[7]) with N6-guest-modified adenosines. These adenosine derivatives were conveniently incorporated into the DNA strand using a post-synthetic approach and formed a selective and stable base pair with complementary thymidine in DNA. Meanwhile, alternate addition of CB[7] and the exchanging guest molecule induced the reversible formation of a duplex structure through the formation and dissociation of a bulky complex on DNA. The kinetics of the reversibility was fine-tuned by changing the size of the modified guest moieties. When incorporated into a specific region of the T7 promoter sequence, the guest-modified adenosines enabled tight and reversible control of in vitro transcription and protein expression in the CFE system. This study marks the first utility of the host-guest interaction for gene expression control in the CFE system, opening new avenues for developing DNA-based technology, particularly for precise gene therapy and DNA nanotechnology.

Overcoming barriers with non-covalent interactions: supramolecular recognition of adamantyl cucurbit[n]uril assemblies for medical applications

Adamantane, a staple in medicinal chemistry, recently became a cornerstone of a supramolecular host-guest drug delivery system, ADA/CB[n]. Owing to a good fit between the adamantane cage and the host cavity of the cucurbit[n]uril macrocycle, formed strong inclusion complexes find applications in drug delivery and controlled drug release. Note that the cucurbit[n]uril host is not solely a delivery vehicle of the ADA/CB[n] system but rather influences the bioactivity and bioavailability of drug molecules and can tune drug properties. Namely, as host-guest interactions are capable of changing the intrinsic properties of the guest molecule, inclusion complexes can become more soluble, bioavailable and more resistant to metabolic conditions compared to individual non-complexed molecules. Such synergistic effects have implications for practical bioapplicability of this complex system and provide a new viewpoint to therapy, beyond the traditional single drug molecule approach. By achieving a balance between guest encapsulation and release, the ADA/CB[n] system has also found use beyond just drug delivery, in fields like bioanalytics, sensing assays, bioimaging, etc. Thus, chemosensing in physiological conditions, indicator displacement assays, in vivo diagnostics and hybrid nanostructures are just some recent examples of the ADA/CB[n] applicability, be it for displacements purposes or as cargo vehicles.

Large anion binding in water

Large water-soluble anions with chaotropic character display surprisingly strong supramolecular interactions in water, for example, with macrocyclic receptors, polymers, biomembranes, and other hydrophobic cavities and interfaces. The high affinity is traced back to a hitherto underestimated driving force, the chaotropic effect, which is orthogonal to the common hydrophobic effect. This review focuses on the binding of large anions with water-soluble macrocyclic hosts, including cyclodextrins, cucurbiturils, bambusurils, biotinurils, and other organic receptors. The high affinity of large anions to molecular receptors has been implemented in several lines of new applications, which are highlighted herein.

Chemical modification of β-cyclodextrin towards hydrogel formation

β-CD is a cyclic oligosaccharide, which has trunked cone like structure. The unique structure makes it efficient for numerous applications. Though, the native β-CD has many issues like low solubility, absence of sufficient functionalities and lower complexation ability with guest molecules. One of the most effective paths to increase the efficiency of cyclodextrins is the generation of polycyclodextrins. In this perspective article, we have summarized the recent reports on the synthetic methods towards the modification of β-CD. Besides, this article reviews the current improvements of two types of β-CD centered supramolecular hydrogels: one is supramolecular hydrogels prepared from CD-based poly(pseudo)rotaxanes and the other is supramolecular hydrogels developed through the host-guest interaction between small guest molecules and CDs. The Polycyclodextrins have established noteworthy applications in several areas ranging from adsorbents for organic pollutants removal to effective carriers of bioactive agents.

Unravelling binding effects in cyclodextrin inclusion complexes with diamondoid ammonium salt guests

A hydrophobic tornado – complexation of diamondoid ammonium salts with cyclodextrins in water.

Cyclodextrins: Structural, Chemical, and Physical Properties, and Applications

Due to their unique structural, physical and chemical properties, cyclodextrins and their derivatives have been of great interest to scientists and researchers in both academia and industry for over a century. Many of the industrial applications of cyclodextrins have arisen from their ability to encapsulate, either partially or fully, other molecules, especially organic compounds. Cyclodextrins are non-toxic oligopolymers of glucose that help to increase the solubility of organic compounds with poor aqueous solubility, can mask odors from foul-smelling compounds, and have been widely studied in the area of drug delivery. In this review, we explore the structural and chemical properties of cyclodextrins that give rise to this encapsulation (i.e., the formation of inclusion complexes) ability. This review is unique from others written on this subject because it provides powerful insights into factors that affect cyclodextrin encapsulation. It also examines these insights in great detail. Later, we provide an overview of some industrial applications of cyclodextrins, while emphasizing the role of encapsulation in these applications. We strongly believe that cyclodextrins will continue to garner interest from scientists for many years to come, and that novel applications of cyclodextrins have yet to be discovered.

Poly(β-Cyclodextrin) Prepared by Ring-Opening Metathesis Polymerization Enables Creation of Supramolecular Polymeric Networks

The controlled synthesis of polymers containing densely grafted cyclodextrin units has proven challenging due to the steric hindrance of these cyclic oligosaccharides. In this study, we report the controlled synthesis of poly(β-cyclodextrin) [poly(β-CD)] through ring-opening metathesis polymerization (ROMP) using Grubbs third-generation catalyst. Molecular weights of >10⁵ g/mol were obtained with dispersity values (Đ) of ≤1.2. In aqueous solution, β-cyclodextrin forms a host-guest complex with adamantyl groups (Ad). These interactions were utilized to prepare supramolecular polymer networks (SPNs) made by adding poly(β-CD) to α,ω-adamantyl-functionalized poly(2-hydroxyethyl acrylate) (Ad-PHEA-Ad). These poly(β-CD)/Ad-PHEA-Ad SPNs were prepared in aqueous solution and then dried to make homogeneous, transparent films. Varying the ratios of the two components enabled structure-property studies via tensile measurements.

Soft Materials by Design: Unconventional Polymer Networks Give Extreme Properties

Hydrogels are polymer networks infiltrated with water. Many biological hydrogels in animal bodies such as muscles, heart valves, cartilages, and tendons possess extreme mechanical properties including being extremely tough, strong, resilient, adhesive, and fatigue-resistant. These mechanical properties are also critical for hydrogels' diverse applications ranging from drug delivery, tissue engineering, medical implants, wound dressings, and contact lenses to sensors, actuators, electronic devices, optical devices, batteries, water harvesters, and soft robots. Whereas numerous hydrogels have been developed over the last few decades, a set of general principles that can rationally guide the design of hydrogels using different materials and fabrication methods for various applications remain a central need in the field of soft materials. This review is aimed at synergistically reporting: (i) general design principles for hydrogels to achieve extreme mechanical and physical properties, (ii) implementation strategies for the design principles using unconventional polymer networks, and (iii) future directions for the orthogonal design of hydrogels to achieve multiple combined mechanical, physical, chemical, and biological properties. Because these design principles and implementation strategies are based on generic polymer networks, they are also applicable to other soft materials including elastomers and organogels. Overall, the review will not only provide comprehensive and systematic guidelines on the rational design of soft materials, but also provoke interdisciplinary discussions on a fundamental question: why does nature select soft materials with unconventional polymer networks to constitute the major parts of animal bodies?

Reversible immobilization of a protein to a gold surface through multiple host–guest interactions

Monolayers were formed by specific interactions between adamantylated proteins (transferrin, lysozyme) and a β-cyclodextrin (β-CD) monolayer on a gold surface.

The Chaotropic Effect as an Assembly Motif in Chemistry

Following up on scattered reports on interactions of conventional chaotropic ions (for example, I- , SCN- , ClO4- ) with macrocyclic host molecules, biomolecules, and hydrophobic neutral surfaces in aqueous solution, the chaotropic effect has recently emerged as a generic driving force for supramolecular assembly, orthogonal to the hydrophobic effect. The chaotropic effect becomes most effective for very large ions that extend beyond the classical Hofmeister scale and that can be referred to as superchaotropic ions (for example, borate clusters and polyoxometalates). In this Minireview, we present a continuous scale of water-solute interactions that includes the solvation of kosmotropic, chaotropic, and hydrophobic solutes, as well as the creation of void space (cavitation). Recent examples for the association of chaotropic anions to hydrophobic synthetic and biological binding sites, lipid bilayers, and surfaces are discussed.

A General Synthetic Route to Isomeric Pyrrolo[1,2- x][1,4]diazepinones

A simple one-pot method for the synthesis of isomeric pyrrolo[1,2- x][1,4]diazepinones in reasonable yields was developed. The method is based on the condensation of readily available N-Boc amino acids with biomass-derived furans containing aminoalkyl groups followed by deprotection, furan ring opening, and Paal-Knorr cyclization. Using this approach, we synthesized pyrrolo[1,2- a][1,4]diazepin-3(2 H)-ones from furfurylamines and β-amino acids and pyrrolo[1,2- d][1,4]diazepin-4(5 H)-ones from 2-(2-furyl)ethylamines and α-amino acids. The cytotoxicity of the synthesized pyrrolodiazepinones was studied.

High-affinity host-guest chemistry of large-ring cyclodextrins

The host-guest chemistry of large-ring cyclodextrins (LRCDs) has been largely unexplored due to the lack of suitable guest molecules that bind with significant affinities to enable potential applications. Herein, we report their complexation with dodecaborate anions (B12X12(2-)), a novel class of guest molecules. The binding constants of the inorganic guests (10(4)-10(6) M(-1)) allow their classification as the first tight binders for LRCDs.

Cyclodextrin-based host–guest supramolecular hydrogel and its application in biomedical fields

CD-based host–guest supramolecular hydrogels and their potential biomedical application.

Host-Guest Complexes of Cyclodextrins and Nanodiamonds as a Strong Non-Covalent Binding Motif for Self-Assembled Nanomaterials

We report the inclusion of carboxy- and amine-substituted molecular nanodiamonds (NDs) adamantane, diamantane, and triamantane by β-cyclodextrin and γ-cyclodextrin (β-CD and γ-CD), which have particularly well-suited hydrophobicity and symmetry for an optimal fit of the host and guest molecules. We studied the host-guest interactions in detail and generally observed 1:1 association of the NDs with the larger γ-CD cavity, but observed 1:2 association for the largest ND in the series (triamantane) with β-CD. We found higher binding affinities for carboxy-substituted NDs than for amine-substituted NDs. Additionally, cyclodextrin vesicles (CDVs) were decorated with d-mannose by using adamantane, diamantane, and triamantane as non-covalent anchors, and the resulting vesicles were compared with the lectin concanavalin A in agglutination experiments. Agglutination was directly correlated to the host-guest association: adamantane showed lower agglutination than di- or triamantane with β-CDV and almost no agglutination with γ-CDV, whereas high agglutination was observed for di- and triamantane with γ-CDV.

Sandwiches of N-doped diamondoids and benzenevialone pair–cation and cation–pi interaction: a DFT study

Cation–lone pair and cation–pi interactions in the complexes of N-doped dimondoids.

Photoresponsive, reversible immobilization of virus particles on supramolecular platforms

Covalently attached azobenzene moieties to cowpea chlorotic mottle virus (CCMV) allow for photoresponsive immobilization on cucurbit[8]uril bearing surfaces.

Study to explore the mechanism to form inclusion complexes of β-cyclodextrin with vitamin molecules

Host–guest inclusion complexes of β-cyclodextrin with two vitamins viz., nicotinic acid and ascorbic acid in aqueous medium have been explored by reliable spectroscopic, physicochemical and calorimetric methods as stabilizer, carrier and regulatory releaser of the guest molecules. Job’s plots have been drawn by UV-visible spectroscopy to confirm the 1:1 stoichiometry of the host-guest assembly. Stereo-chemical nature of the inclusion complexes has been explained by 2D NMR spectroscopy. Surface tension and conductivity studies further support the inclusion process. Association constants for the vitamin-β-CD inclusion complexes have been calculated by UV-visible spectroscopy using both Benesi–Hildebrand method and non-linear programme, while the thermodynamic parameters have been estimated with the help of van’t Hoff equation. Isothermal titration calorimetric studies have been performed to determine the stoichiometry, association constant and thermodynamic parameters with high accuracy. The outcomes reveal that there is a drop in ΔS^o, which is overcome by higher negative value of ΔH^o, making the overall inclusion process thermodynamically favorable. The association constant is found to be higher for ascorbic acid than that for nicotinic acid, which has been explained on the basis of their molecular structures.

Water Structure Recovery in Chaotropic Anion Recognition: High-Affinity Binding of Dodecaborate Clusters to γ-Cyclodextrin

Dodecaborate anions of the type B12X12(2-) and B12X11Y(2-) (X=H, Cl, Br, I and Y=OH, SH, NH3(+), NR3(+)) form strong (K(a) up to 10(6) L mol(-1), for B12Br12(2-)) inclusion complexes with γ-cyclodextrin (γ-CD). The micromolar affinities reached are the highest known for this native CD. The complexation exhibits highly negative enthalpies (up to -25 kcal mol(-1)) and entropies (TΔS up to -18.4 kcal mol(-1), both for B12I12(2-)), which position these guests at the bottom end of the well-known enthalpy-entropy correlation for CDs. The high driving force can be traced back to a chaotropic effect, according to which chaotropic anions have an intrinsic affinity to hydrophobic cavities in aqueous solution. In line with this argument, salting-in effects revealed dodecaborates as superchaotropic dianions.

Coiled coil driven membrane fusion between cyclodextrin vesicles and liposomes

Controlled fusion events between natural membranes composed of phospholipids with synthetic unnatural membranes will yield valuable fundamental information on the mechanism of membrane fusion. Here, fusion between vastly different phospholipid liposomes and cyclodextrin amphiphile based vesicles (CDVs) controlled by a pair of coiled coil forming lipidated peptides was investigated. Fusion events were characterized using lipid and content mixing assays and the resulting hybrid assemblies were characterized with cryo-TEM imaging. The secondary/quaternary structure of the lipidated peptides at the membrane interface was studied using circular dichroism spectroscopy. This is the first example of targeted fusion between natural and non-natural bilayer membranes and the in situ formation of hybrid CDV-liposome structures is of interest as it yields fundamental information about the mechanism through which fusion proceeds.

Diamond nanowires: fabrication, structure, properties, and applications

C(sp(3) )C-bonded diamond nanowires are wide band gap semiconductors that exhibit a combination of superior properties such as negative electron affinity, chemical inertness, high Young's modulus, the highest hardness, and room-temperature thermal conductivity. The creation of 1D diamond nanowires with their giant surface-to-volume ratio enhancements makes it possible to control and enhance the fundamental properties of diamond. Although theoretical comparisons with carbon nanotubes have shown that diamond nanowires are energetically and mechanically viable structures, reproducibly synthesizing the crystalline diamond nanowires has remained challenging. We present a comprehensive, up-to-date review of diamond nanowires, including a discussion of their synthesis along with their structures, properties, and applications.