Nonlinear Amplification of a Supramolecular Complex at a Multivalent Interface

Fabrication of Host-Guest Complexes between Adamantane-Functionalized 1,3,4-Oxadiazoles and β-Cyclodextrin with Improved Control Efficiency against Intractable Plant Bacterial Diseases

Supramolecular chemistry provides huge potentials and opportunities in agricultural pest management. In an attempt to develop highly bioactive, eco-friendly, and biocompatible supramolecular complexes for managing intractable plant bacterial diseases, herein, a type of interesting adamantane-functionalized 1,3,4-oxadiazole was rationally prepared to facilitate the formation of supramolecular complexes via β-cyclodextrin-adamantane host-guest interactions. Initial antibacterial screening revealed that most of these adamantane-decorated 1,3,4-oxadiazoles were obviously bioactive against three typically destructive phytopathogens. The lowest EC₅₀ values could reach 0.936 (III₁₈), 0.889 (III₁₈), and 2.10 (III₁₉) μg/mL against the corresponding Xanthomonas oryzae pv. oryzae (Xoo), Xanthomonas axonopodis pv. citri (Xac), and Pseudomonas syringae pv. actinidiae (Psa). Next, the representative supramolecular binary complex III₁₈@β-CD (binding mode 1:1) was successfully fabricated and characterized by ¹H nuclear magnetic resonance (NMR), isothermal titration calorimetry (ITC), high-resolution mass spectrometry (HRMS), dynamic light scattering (DLS), and transmission electron microscopy (TEM). Eventually, correlative water solubility and foliar surface wettability were significantly improved after the formation of host-guest assemblies. In vivo antibacterial evaluation found that the achieved supramolecular complex could distinctly alleviate the disease symptoms and promote the control efficiencies against rice bacterial blight (from 34.6-35.7% (III₁₈) to 40.3-43.6% (III₁₈@β-CD)) and kiwi canker diseases (from 41.0-42.3% (III₁₈) to 53.9-68.0% (III₁₈@β-CD)) at 200 μg/mL (active ingredient). The current study can provide a feasible platform and insight for constructing biocompatible supramolecular assemblies for managing destructive bacterial infections in agriculture.

Luminescent detection of Ochratoxin A using terbium chelated mesoporous silica nanoparticles

This work represents the time-resolved fluorescence detection of Ochratoxin A (OTA), a highly toxic and commonly found toxin in food stuffs, by a terbium (Tb³⁺) chelated nanoparticle sensor with high sensitivity and remarkable selectivity. The coordination of OTA to Tb³⁺ center on nanoparticle surface resulted in the significant enhancement of the fluorescence signal in nanomolar concentrations with a detection limit of 20 ppb. In contrast, no enhancements were observed in the presence of other common mycotoxins such as Aflatoxin B1, Zearalenone, Citrinin and Patulin. The results indicate that the Tb³⁺ chelated nanoparticle sensor has great potential for applications in food analysis and safety.

Cyclodextrin-based complex coacervate core micelles with tuneable supramolecular host-guest, metal-to-ligand and charge interactions

Micelles have been recognized as versatile platforms for different biomedical applications, from bioimaging to drug delivery. Complex coacervate core micelles present great advantages compared to traditional micelles, however controlling the number of charges per core-unit and the stability is still a challenge. We here present cyclodextrin-based complex coacervate core micelles where the charge per core-unit can be straightforwardly tuned by cyclodextrin host-guest interactions. By varying the ratio between two adamantane guest molecules, 1-adamantanecarboxylic acid and 1,3-adamantanediacetic acid, the charge of the monomeric core-units can be finely tuned from 6- to 9-. By adding an adamantane bislinker, monomeric core-units can be combined together in dimeric and polymeric structures, increasing the micelles' stability. The orthogonal supramolecular host-guest and coordination-chemistry allows for well-controlled cyclodextrin-based complex coacervate core micelles that offer a versatile platform for designing future, e.g., responsive systems.

Macroscopic Supramolecular Assembly through Electrostatic Interactions Based on a Flexible Spacing Coating

Macroscopic supramolecular assembly (MSA) is a recent advance in supramolecular chemistry that involves associating large building blocks with a size larger than 10 µm through noncovalent interactions. However, until now the applicable material system is rather limited to hydrogels, and MSA of rigid materials with supramolecular interactions widely used in molecular assembly has rarely been reported due to the difficulty in achieving multivalency between rigid surfaces. Herein, the concept of flexible spacing coating is applied with highly flowable properties, and the electrostatic-interaction-driven MSA of relatively rigid polydimethylsiloxane building blocks is demonstrated. With the flexible spacing coating of a polyelectrolyte multilayer, the oppositely charged rigid building blocks can realize MSA under shaking in water for 5 min. The major contribution of the electrostatic interaction is confirmed by both qualitative controlled MSA experiments in other solvents, disassembly in ionic solution and quantitative results with an in situ force measurement method.

Lanthanide-Dipicolinic Acid Coordination Driven Micelles with Enhanced Stability and Tunable Function

Lanthanide-incorporated polymer micelles have been prepared driven by the lanthanide-dipicolinic acid (Ln-DPA) coordination. The terdentate DPA ligand is grafted to the PVP block of a diblock copolymer poly(4-vinylpyridine)-b-poly(ethylene oxide) (P4VP48-b-PEO193). Upon addition of Eu(III) ions to a solution of the DPA16-g-P4VP48-b-PEO193 block copolymer, intermolecular cross-links form and the ligand-carrying blocks assemble, leading to the formation of micelles, stabilized by the hydrophilic PEO blocks. The DPA exhibits a dual function in this study. First, the chelate group strongly coordinates to Eu(III) in a three to one ratio, and leads to high stability of the formed micelles, as proven by light scattering and luminescence spectroscopy. Second, DPA acts as an antenna that transfers energy to the Eu(III) ion and dramatically enhances the luminescence emission. The Eu(III) emission is moreover most sensitive for local environment and allows to shine light on the internal structure of this class of self-assembled 36 nm size soft nanoparticles. With the same strategy gadolinium(III) can be incorporated providing micelles which show enhanced magnetic relaxation rates. Micelles capping a mixture of Eu(III) and Gd(III) show both enhanced luminescence emission and magnetic relaxation rates, and the functions can be tuned by regulating the mixing ratio of Eu(III) and Gd(III), showing great potential for developing multimodal imaging agents for diagnostic as well as therapeutic applications.

Recent advances in engineering polyvalent biological interactions

Polyvalent interactions, where multiple ligands and receptors interact simultaneously, are ubiquitous in nature. Synthetic polyvalent molecules, therefore, have the ability to affect biological processes ranging from protein-ligand binding to cellular signaling. In this review, we discuss recent advances in polyvalent scaffold design and applications. First, we will describe recent developments in the engineering of polyvalent scaffolds based on biomolecules and novel materials. Then, we will illustrate how polyvalent molecules are finding applications as toxin and pathogen inhibitors, targeting molecules, immune response modulators, and cellular effectors.