Kinetic Analysis and Mechanism of the Hydrolytic Degradation of Squaramides and Squaramic Acids

Squaramide Formation for DNA-Encoded Library Synthesis

DNA-encoded libraries (DELs) can be considered as one of the most powerful tools for the discovery of small molecules of biological interest. However, the ability to access large DELs is contingent upon having chemical transformations that work in aqueous phase and generate minimal DNA alterations and the availability of building blocks compatible with on-DNA chemistry. In addition, accessing scaffolds of interest to medicinal chemists can be challenging in a DEL setting because of inherent limitations of DNA-supported chemistry. In this context, a squaramide formation reaction was developed by using a two-step process. The mild and high-yielding reaction tolerates a wide array of functional groups and was shown to be safe for DNA, thereby making this methodology ideal for DELs.

From Benznidazole to New Drugs: Nanotechnology Contribution in Chagas Disease

Chagas disease is a neglected tropical disease caused by the protozoan Trypanosoma cruzi. Benznidazole and nifurtimox are the two approved drugs for their treatment, but both drugs present side effects and efficacy problems, especially in the chronic phase of this disease. Therefore, new molecules have been tested with promising results aiming for strategic targeting action against T. cruzi. Several studies involve in vitro screening, but a considerable number of in vivo studies describe drug bioavailability increment, drug stability, toxicity assessment, and mainly the efficacy of new drugs and formulations. In this context, new drug delivery systems, such as nanotechnology systems, have been developed for these purposes. Some nanocarriers are able to interact with the immune system of the vertebrate host, modulating the immune response to the elimination of pathogenic microorganisms. In this overview of nanotechnology-based delivery strategies for established and new antichagasic agents, different strategies, and limitations of a wide class of nanocarriers are explored, as new perspectives in the treatment and monitoring of Chagas disease.

Lithium Pyrene Squarate Covalent Organic Frameworks for Efficient Lithium and Magnesium Separation from Salt Water

The increasing pressure for lithium resources from the electric vehicle and nuclear energy industries means that new technologies to separate Mg²⁺ from Li⁺ from salt water are in demand. To address this need, we fabricated lithium pyrene squarate covalent organic frameworks (Li-SQCOFs) to separate Mg²⁺/Li⁺ mixtures from salt water. We optimized the effect of the electrolyte and the amount of the adsorbent and then carried out a kinetics study on the adsorbent recovery at various pH levels using both batch and continuous flow adsorption methods. Li-SQCOF was found to have excellent selectivity for solutions containing a mixture of Mg²⁺/Li⁺ ions. This work represents a unique path for the separation of Mg²⁺/Li⁺ through direct adsorption using a covalent organic framework (COF). The COF-supported ultrafiltration bed made in this study gave a Mg²⁺ separation flux of 60.5 h^-1 m^-2.

Amidosquaramides - a new anion binding motif with pH sensitive anion transport properties

Stimuli responsive anion transport is becoming an important aspect of supramolecular anion recognition chemistry. Herein, we report the synthesis of a family of anion receptors that incorporate a new anion binding motif, amidosquaramides. We show using experimental and computational methods that these receptors have pK_a values close to physiological pH but also display intramolecular H-bonding interactions that affect anion recognition. Moreover, moderate activity in a Cl^-/NO₃^- exchange assay is observed at physiological pH that can be effectively 'switched on' when repeated under acidic conditions. The reported findings provide synthetic methods that can be used for the construction of more complex squaramide based anion receptors and also provide insight into the importance of conformational analysis when considering receptor design.

Squaric acid as a new chemoselective moiety for mass spectrometry-based metabolomics analysis of amines

The investigation of microbiome-derived metabolites is important to understand metabolic interactions with their human host. New methodologies for mass spectrometric discovery of undetected metabolites with unknown bioactivity are required. Herein, we introduce squaric acid as a new chemoselective moiety for amine metabolite analysis in human fecal samples.

Introducing a squaramide-based self-immolative spacer for controlled drug release

Herein we report the design, synthesis and assessment of the first example of a squaramide-based self-immolative system triggered by an enzymatic reduction.

Liposomes Composed by Membrane Lipid Extracts from Macrophage Cell Line as a Delivery of the Trypanocidal N,N'-Squaramide 17 towards Trypanosoma cruzi

Chagas is a neglected tropical disease caused by Trypanosoma cruzi, and affects about 25 million people worldwide. N, N’-Squaramide 17 (S) is a trypanocidal compound with relevant in vivo effectiveness. Here, we produced, characterized, and evaluated cytotoxic and trypanocidal effects of macrophage-mimetic liposomes from lipids extracted of RAW 264.7 cells to release S. As results, the average hydrodynamic diameter and Zeta potential of mimetic lipid membranes containing S (MLS) was 196.5 ± 11 nm and −61.43 ± 2.3 mV, respectively. Drug entrapment efficiency was 73.35% ± 2.05%. After a 72 h treatment, MLS was observed to be active against epimastigotes in vitro (IC₅₀ = 15.85 ± 4.82 μM) and intracellular amastigotes (IC₅₀ = 24.92 ± 4.80 μM). Also, it induced low cytotoxicity with CC₅₀ of 1199.50 ± 1.22 μM towards VERO cells and of 1973.97 ± 5.98 μM in RAW 264.7. MLS also induced fissures in parasite membrane with a diameter of approximately 200 nm in epimastigotes. MLS showed low cytotoxicity in mammalian cells and high trypanocidal activity revealing this nanostructure a promising candidate for the development of Chagas disease treatment.

Receptors for sulfate that function across a wide pH range in mixed aqueous-DMSO media

Water soluble squaramide macrocycles (MSQs) display high sulfate binding affinities in aqueous DMSO mixtures. The introduction of pyridine spacers into the macrocycles resulted in increased sulfate binding affinity in comparison to compounds with benzene spacers. [3]MSQ 6 was found to be a selective ligand for SO42- in highly competitive conditions and over a wide pH range (3.2-14).

Surface Modification of Pseudoboehmite-Coated Aluminum Plates with Squaramic Acid Amphiphiles

The functionalization of interfaces has become very important for the protection or modification of metal (metal oxides) surfaces. The functionalization of aluminum is particularly interesting because of its relevance in fabricating components for electronic devices. In this work, the utilization of squaramic acids for the functionalization of aluminum substrates is reported for the first time. The physicochemical properties of the interfaces rendered by n-alkyl squaramic acids on aluminum metal substrates coated with pseudoboehmite [Al(O)x(OH)y] layers are characterized by contact angle, grazing-angle Fourier-transform infrared spectroscopy, atomic force microscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, and matrix-assisted laser desorption ionization time-of-flight. Moreover, we could confirm the squaramic functionalization of the substrates by diffuse reflectance UV-vis spectroscopy, which cannot be used for the characterization of UV-vis-inactive substrates such as carboxylates and phosphonates, commonly used for coating metallic surfaces. Remarkably, the results of sorption experiments indicate that long-chain alkyl squaramic acid desorbs from activated-aluminum substrates at a reduced rate compared to palmitic acid, a carboxylic acid frequently used for the functionalization of metal oxide surfaces. Theoretical calculations indicate that the improved anchoring properties of squaramic acids over carboxylates are probably due to the formation of additional hydrogen bonding interactions on the interface. Accordingly, we propose N-alkyl squaramic acids as new moieties for efficient functionalization of metal oxides.

Synthesis and biological evaluation of new long-chain squaramides as anti-chagasic agents in the BALB/c mouse model

Chagas Disease is caused by infection with the insect-transmitted protozoan Trypanosoma cruzi and affects more than 10 million people. It is a paradigmatic example of a chronic disease without an effective treatment in Latin America where the current therapies, based on Benznidazole and Nifurtimox, are characterised by limited efficacy, toxic side-effects and frequent failures in the treatment. We present a series of new long-chain squaramides, identified based on their ¹H and ¹³C NMR spectra, and their trypanocidal activity and cytotoxicity were tested in vitro through the determination of IC₅₀ values. Compounds 4 and 7 were more active and less toxic than the reference drug Benznidazole, and these results were the basis of promoting in vivo assays, where parasitaemia levels, assignment of cure, reactivation of parasitaemia and others parameters were determined in mice treated in both the acute and chronic phases. Finally, the mechanisms of action were elucidated at metabolic and mitochondrial levels and superoxide dismutase inhibition. The experiments allowed us to select compound 7 as a promising candidate for treating Chagas Disease, where the activity, stability and low cost make long-chain squaramides appropriate molecules for the development of an affordable anti-chagasic agent versus current treatments.