Access to basic drugs is a major issue in developing countries. Chagas disease caused by Trypanosoma cruzi is a paradigmatic example of a chronic disease without an effective treatment. Current treatments based on benznidazole and nifurtimox are expensive, ineffective, and toxic. N,N'-Squaramides are amide-type compounds that feature both hydrogen bond donor and acceptor groups and are capable of multiple interactions with complementary sites. When combined with amine and carboxylic groups, squaramide compounds have increased solubility and therefore make suitable therapeutic agents. In this work, we introduce a group of Lipinski's rule of five compliant squaramides as candidates for treating Chagas disease. The in vivo studies confirmed the positive expectations arising from the preliminary in vitro studies, revealing compound 17 to be the most effective for both acute and chronic phases. The activity, stability, low cost of starting materials, and straightforward synthesis make amino squaramides appropriate molecules for the development of an affordable anti-Chagasic agent.

Capsaicin (CAP) has been long known for its analgesic properties and more recently for its antitumor activity in various cell types.However,its pungency and the high doses needed to achieve as ignificant activity have precluded its application in cancer therapy. Herein, we propose astraightforward novel strategy to improve the antitumor effect of CAP based on the enhancement of its aggregation propensity in aqueous media by covalent attachment of aB ODIPY (BDP) dye.T he target CAP-BDP 1 self-assembles in aqueous solutions into weakly fluorescent globular assemblies that become highly emissive upon cell uptake-induced disassembly. Remarkably,due to the improved delivery to the tumour tissue upon aggregation, we have succeeded in reducing the doses of CAP-based drugs in vivo in prostate cancer by two orders of magnitude while maintaining as ubstantial antitumor activity.

New tripodal squaramide-based hosts have been synthesised and structurally characterised by spectroscopic methods. In 2.5 % (v/v) [D(6)]DMSO in CDCl(3), compound 4 formed dimeric assemblies [log K(dim)=3.68(8)] as demonstrated by (1)H NMR spectroscopy and UV dilution experiments. AFM and SEM analyses revealed the formation of a network of bundled fibres, which indicates a preferential mechanism for aggregation. These C(3)-symmetric tripodal hosts exhibited two different and mutually exclusive modes of binding, each one easily accessible by simultaneous reorientation of the squaramide groups. In the first, a convergent disposition of the NH squaramide protons allowed the formation of an array of N-H⋅⋅⋅X(-) hydrogen bonds with anions. In the second mode, reorientation of carbonyl squaramide groups allowed multiple C=O⋅⋅⋅H interactions with ammonium cations. The titration of 4 with different tetraalkylammonium iodides persistently showed the formation of 1:1 complexes, as well as 1:2 and 1:3 complexes. The corresponding stoichiometries and binding affinities of the complexes were evaluated by multi-regression analysis. The formation of high-order complexes, supported by ROESY, NOESY and mass spectrometry experiments, has been attributed to the insertion of NR(4)I ion pairs between the carbonyl and NH protons of the squaramide groups located in adjacent arms of 4. The observed effects reflect the induction of significant conformational changes in the hosts, mainly in relation to the relative orientation of the squaramide groups adapting their geometries to incoming ion-pair complementary substrates. The results presented herein identify and fully describe two different modes of ion-pair recognition aimed at directing conformational transitions in the host, therefore establishing a base for controlling more elaborate movements of molecular devices through ion-pair recognition.

Cell internalization is a major issue in drug design. Although squaramide-based compounds are receiving much attention because of their interesting bioactivity, cell uptake and trafficking within cells of this type of compounds are still unknown. In order to monitor the cell internalization process of cyclosquaramide compounds we have prepared two fluorescent probes by covalently linking a fluorescent dye (BODIPY derivative or fluorescein) to a noncytotoxic cyclosquaramide framework. These two probes (C2-BDP and C2-FITC) rapidly internalize across live cell membranes through endocytic receptor-mediated mechanisms. Due to its higher fluorescence and photochemical stability, C2-BDP is a superior dye than C2-FITC. C2-BDP remains sequestered in late endosomes allowing their fast and selective imaging in various live cell types. Cyclosquaramide-cell membrane interactions facilitate cell uptake and have been investigated by binding studies in solution as well as in live cells. Cyclosquaramide 1 (C2-BDP) can be used as a highly fluorescent probe for the rapid and selective imaging of late endosomes in live cells.