Binding of Bioactive Ammonium Ions in Water with a Cavity-Based Selectivity: Water Solubilization versus Micellar Incorporation.

Many bioactive molecules contain primary ammonium groups, generating significant interest in developing selective receptors for ammonium ions. A promising strategy involves the use of polyaromatic cavitands to achieve size and shape selectivity through their cavity. However, designing effective receptors for ammonium ions in aqueous media is challenging due to the competitive nature of water.

Calixarene-coated gold nanorods as robust photothermal agents.

Gold nanorods (AuNRs) hold considerable promise for their use in biomedical applications, notably in the context of photothermal therapy (PTT). Yet, their anisotropic nature presents a notable hurdle. Under laser irradiation, these structures are prone to deformation, leading to changes in their optical and photothermal properties over time.

Multiplexed immunolabelling of cancer using bioconjugated plasmonic gold-silver alloy nanoparticles.

Reliable protein detection methods are vital for advancing biological research and medical diagnostics. While immunohistochemistry and immunofluorescence are commonly employed, their limitations underscore the necessity for alternative approaches. This study introduces immunoplasmonic labelling, utilizing plasmonic nanoparticles (NPs), specifically designed gold and gold-silver alloy NPs (Au:Ag NPs), for multiplexed and quantitative protein detection.

Multipodal Au-C grafting of calix[4]arene molecules on gold nanorods.

The interface robustness and spatial arrangement of functional molecules on metallic nanomaterials play a key part in the potential applications of functional nano-objects. The design of mechanically stable and electronically coupled attachments with the underlying metal is essential to bring specific desirable properties to the resulting hybrid materials. In this context, rigid multipodal platforms constitute a unique opportunity for the controllable grafting of functionality.

Development of a Cone Homooxacalix[3]arene-Based Fluorescent Chemosensor for the Selective Detection of Biogenic Ammonium Ions in Protic Solvents.

We report here on the development of a fluorescent cone homooxacalix[3]arene-based receptor with a pyrene unit on the wide rim of the macrocycle () for the selective detection of primary ammonium ions, including those of biological importance. was synthesized efficiently via an innovative strategy that enables the regio- and iteroselective wide rim functionalization of the readily available -Bu-substituted homooxacalix[3]arene precursor. Nuclear magnetic resonance studies and methods highlighted the -complexation of primary ammonium ions, including the protonated form of biogenic dopamine, tryptamine, serotonin, mexamine, and 3-iodothyronamine.

Synthesis of -Symmetrical 1,3,5-Tris-Protected Calix[6]arene-Based Molecular Platforms.

Few synthetic methodologies that yield tris-functionalized -symmetrical calix[6]arenes have been reported. In this work, three allyl protecting groups are selectively placed in 1,3,5 alternate positions of three pristine calix[6]arenes, each differing by their substituent on the large rim, resulting in three new -symmetrical molecular platforms. Removal of the protecting allylic groups gives access to sophisticated calix[6]arenes that can be further modified.

Photo-Catalyzed α-Arylation of Enol Acetate Using Recyclable Silica-Supported Heteroleptic and Homoleptic Copper(I) Photosensitizers.

Earth-abundant photosensitizers are highly sought after for light-mediated applications, such as photoredox catalysis, depollution and energy conversion schemes. Homoleptic and heteroleptic copper(I) complexes are promising candidates in this field, as copper is abundant and the corresponding complexes are easily obtained in smooth conditions. However, some heteroleptic copper(I) complexes suffer from low (photo)stability that leads to the gradual formation of the corresponding homoleptic complex.

Selective binding of oxalate by a tris-ureido calix[6]tube in a protic environment.

Due to their significant role in industry and biological systems, the interest in selectively recognizing and detecting small dicarboxylates has grown in recent years. In this study, we report on the binding properties of a family of tubular-shaped heterotritopic receptors based on bis-calix[6]arenes, which contain three (thio)urea bridges (C3U and C3TU) or six urea bridges (C6U), toward dicarboxylates. While poor binding properties were observed by NMR for the newly synthesized C6U, receptors C3U and C3TU exhibited a unique ability to cooperatively complex a dicarboxylate anion sandwiched between two ammonium ions.

Ultra-stable silver nanoplates: efficient and versatile colorimetric reporters for dipstick assays.

Noble metal anisotropic nanostructures, such as silver nanoplates (AgNPls), are interesting because they possess enhanced plasmonic properties compared to their spherical counterparts: increased extinction coefficient and tunable maximum of absorption wavelength. However, their use for biosensing application is limited as these structures are intrinsically unstable and, to maintain the anisotropic structure, a coating protecting the metallic surface is required. In this work, we report on the capacity of a thin but robust coating based on calixarene-diazonium salts to maintain the structure anisotropy of silver nanoplates in conditions in which traditionally used coatings fail.

Empirical Optimization of Peptide Sequence and Nanoparticle Colloidal Stability: The Impact of Surface Ligands and Implications for Colorimetric Sensing.

Surface ligands play a critical role in controlling and defining the properties of colloidal nanocrystals. These aspects have been exploited to design nanoparticle aggregation-based colorimetric sensors. Here, we coated 13-nm gold nanoparticles (AuNPs) with a large library of ligands (, from labile monodentate monomers to multicoordinating macromolecules) and evaluated their aggregation propensity in the presence of three peptides containing charged, thiolate, or aromatic amino acids.

Photosensitized Activation of Diazonium Derivatives for C-B Bond Formation.

Aryl diazonium salts are ubiquitous building blocks in chemistry, as they are useful radical precursors in organic synthesis as well as for the functionalization of solid materials. They can be reduced electrochemically or through a photo-induced electron transfer reaction. Here we provide a detailed picture of the ground and excited-state reactivity of a series of 9 rare and earth abundant photosensitizers with 13 aryl diazonium salts, which also included 3 macrocyclic calix[4]arene tetradiazonium salts.

A fluoride-induced aggregation test to quickly assess the efficiency of ligand exchange procedures from citrate capped AuNPs.

Hypothesis: Citrate capped gold nanoparticles (AuNPs-citrate) are the starting material for most of the academic and industrial applications using gold nanoparticles. AuNPs-citrate must usually be functionalized with organic (bio)molecules, through a ligand exchange process, to become suitable for the envisaged application. The evaluation of the efficiency of the ligand-exchange process with a simple and convenient procedure is challenging.

A 4-state acid-base controlled molecular switch based on a host-guest system.

A novel Zn funnel complex that presents three phenol functions within a calix[6]arene macrocycle is described. Host-guest studies, monitored by H NMR spectroscopy, evaluate the impact of the replacement of three anisole moieties present in a previously described system with phenols. It is now shown that the dicationic complex is responsive to anions, whereas deprotonation of one phenol unit completely inhibits any hosting response.

Selective Metal-ion Complexation of a Biomimetic Calix[6]arene Funnel Cavity Functionalized with Phenol or Quinone.

In the biomimetic context, many studies have evidenced the importance of the 1 and 2 coordination sphere of a metal ion for controlling its properties. Here, we propose to evaluate a yet poorly explored aspect, which is the nature of the cavity that surrounds the metal labile site. Three calix[6]arene-based aza-ligands are compared, that differ only by the nature of cavity walls, anisole, phenol or quinone (L , L and L ).

Specific Binding of Primary Ammoniums in Aqueous Media by Homooxacalixarenes Incorporated into Micelles.

The development of artificial receptors for efficient recognition of analytes in water is a challenging task. Homooxacalix[3]arene-based receptor , which is selective toward primary ammoniums in organic solvents, was transferred into water following two different strategies: direct solubilization and micellar incorporation. Extensive H NMR studies showed that recognition of ammoniums is only observed in the case of micellar incorporation, highlighting the beneficial effect of the microenvironment of the micellar core.

Bifunctional Calix[4]arene-Coated Gold Nanoparticles for Orthogonal Conjugation.

Gold nanoparticles (AuNPs) are currently intensively exploited in the biomedical field as they possess interesting chemical and optical properties. Although their synthesis is well-known, their controlled surface modification with defined densities of ligands such as peptides, DNA, or antibodies remains challenging and has generally to be optimized case by case. This is particularly true for applications like in vivo drug delivery that require AuNPs with multiple ligands, for example a targeting ligand and a drug in well-defined proportions.

Ultrastable Silver Nanoparticles for Rapid Serology Detection of Anti-SARS-CoV-2 Immunoglobulins G.

Dipstick assays using silver nanoparticles (AgNPs) stabilized by a thin calix[4]arene-based coating were developed and used for the detection of Anti-SARS-CoV-2 IgG in clinical samples. The calixarene-based coating enabled the covalent bioconjugation of the SARS-CoV-2 Spike Protein via the classical EDC/sulfo-NHS procedure. It further conferred remarkable stability to the resulting bioconjugated AgNPs, as no degradation was observed over several months.

Calix[6]arenes with halogen bond donor groups as selective and efficient anion transporters.

Here we present the anion binding and anion transport properties of a series of calix[6]arenes decorated on their small rim with either halogen bond or hydrogen bond donating groups. We show that the halogen bond donating iodotriazole groups enable highly selective transport of chloride and nitrate anions, without transport of protons or hydroxide, at rates similar to those observed with thiourea or squaramide groups.

Peptide-Conjugated Silver Nanoparticles for the Colorimetric Detection of the Oncoprotein Mdm2 in Human Serum.

Invited for this month's cover are the collaborating groups of Prof. Gilles Bruylants and Prof. Ivan Jabin, Université libre de Bruxelles, Belgium.

Peptide-Conjugated Silver Nanoparticles for the Colorimetric Detection of the Oncoprotein Mdm2 in Human Serum.

The development of efficient, reliable, and easy-to-use biosensors allowing early cancer diagnosis is of paramount importance for patients. Herein, we report a biosensor based on silver nanoparticles functionalized by peptide aptamers for the detection of a cancer biomarker, i. e.

A Water Molecule Triggers Guest Exchange at a Mono-Zinc Centre Confined in a Biomimetic Calixarene Pocket: A Model for Understanding Ligand Stability in Zn Proteins.

Invited for the cover of this issue are Kristin Bartik, Olivia Reinaud and co-workers at the Université libre de Bruxelles and Université Paris Descartes. The image depicts a Zn protein and highlights the role that a single water molecule can play in catalysing ligand exchange. Read the full text of the article at 10.

Closing a Calix[6]arene-Based Funnel Zn Complex at Its Large Rim Entrance: Consequences on Metal Ion Affinity and Host-Guest Properties.

A molecular capsule based on a calix[6]arene core closed at the small rim by a three-point coordinated metal ion and at the large rim by a three-point covalent capping is described. It is derived from a trisimidazole funnel complex capped by a trenamide unit that prevents in/out exchange of guest molecules through the large rim. A detailed comparative study with three different calixarenes provides a unique opportunity for (i) comparing the binding ability of two different coordination sites in well three-dimensional (3D)-structured macrocyclic receptors and (ii) evaluating the impact of a covalent closing of one rim of a funnel receptor while the other rim is closed by weaker coordination bonds.