In silico prediction of ADMET parameters and in vitro evaluation of antioxidant and cytotoxic activities promoted by indole-thiosemicarbazone compounds.

Cancer is a complex and multifactorial disease characterized by uncontrolled cell growth and is one of the main causes of death in the world. This work aimed to evaluate a small series of 10 different indole-thiosemicarbazone compounds as potential antitumor agents. This is a pioneering study. For this, the antioxidant and cytotoxic capacity against normal and tumor cells was evaluated. The results showed that the compounds were able to promote moderate to low antioxidant activity for the ABTS radical scavenging assay. ADMET in silico assays showed that the compounds exhibited good oral bioavailability. As for toxicity, they were able to promote low cytotoxicity against normal cells, in addition to not being hemolytic. The compounds showed promising in vitro antitumor activity against the T47D, MCF-7, Jurkat and DU-145 strains, not being able to inhibit the growth of the Hepg2 strain. Through this in vitro study, it can be concluded that the compounds are potential candidates for antitumor agents.

Preliminary evaluation of the toxicological, antioxidant and antitumor activities promoted by the compounds 2,4-dihydroxy-benzylidene-thiosemicarbazones an in silico, in vitro and in vivo study.

Thiosemicarbazones are promising classes of compounds with antitumor activity. For this study, six 2,4-dihydroxy-benzylidene-thiosemicarbazones compounds were synthesized. These compounds were submitted to different assays in silico, in vitro and in vivo to evaluate the toxicological, antioxidant and antitumor effects. The in silico results were evaluated by the SwissADME and pkCSM platforms and showed that all compounds had good oral bioavailability profiles. The in vitro and in vivo toxicity assays showed that the compounds showed low cytotoxicity against different normal cells and did not promote hemolytic effects. The single dose acute toxicity test (2000 mg/kg) showed that none of the compounds were toxic to mice. In in vitro antioxidant activity assays, the compounds showed moderate to low activity, with PB17 standing out for the ABTS radical capture assay. The in vivo antioxidant activity highlighted the compounds 1, 6 and 8 that promoted a significant increase in the concentration of liver antioxidant enzymes. Finally, all compounds showed promising antitumor activity against different cell lines, especially MCF-7 and DU145 lines, in addition, they inhibited the growth of sarcoma 180 at concentrations lower than 50 mg/kg. These results showed that the evaluated compounds can be considered as potential antitumor agents.

Alpha-hemolysin nanopore allows discrimination of the microcystins variants.

Microcystins (MCs) are a class of cyclic heptapeptides with more than 100 variants produced by cyanobacteria present in surface waters. MCs are potent hepatotoxic agents responsible for fatal poisoning in animals and humans. Several techniques are employed in the detection of MCs, however, there is a shortage of methods capable of discriminating variants of MCs. In this work we demonstrate that the α-hemolysin (αHL) nanopore can detect and discriminate the variants (LR, YR and RR) of MCs in aqueous solution. The discrimination process is based on the analysis of the residence times of each variant of MCs within the unitary nanopore, as well as, on the amplitudes of the blockages in the ionic current flowing through it. Simulations of molecular dynamics and calculation of the electrostatic potential revealed that the variants of MCs present different charge distribution and correlated with the three patterns on the amplitudes of the blockages in the ionic current. Additionally, molecular docking analysis indicates different patterns of interaction of the variants of MCs with two specific regions of the nanopore. We conclude that αHL nanopore can discriminate variants of microcystins by a mechanism based mainly on electrostatic interaction. Finally, we propose the use of nanopore-based technology as a promising method for analyzing microcystins in aqueous solutions.

Hofmeister effect in confined spaces: halogen ions and single molecule detection.

Despite extensive research in the nanopore-sensing field, there is a paucity of experimental studies that investigate specific ion effects in confined spaces, such as in nanopores. Here, the effect of halogen anions on a simple bimolecular complexation reaction between monodisperse poly(ethylene glycol) (PEG) and α-hemolysin nanoscale pores have been investigated at the single-molecule level. The anions track the Hofmeister ranking according to their influence upon the on-rate constant. An inverse relationship was demonstrated for the off-rate and the solubility of PEG. The difference among anions spans several hundredfold. Halogen anions play a very significant role in the interaction of PEG with nanopores although, unlike K(+), they do not bind to PEG. The specific effect appears dominated by a hydration-dehydration process where ions and PEG compete for water. Our findings provide what we believe to be novel insights into physicochemical mechanisms involved in single-molecule interactions with nanopores and are clearly relevant to more complicated chemical and biological processes involving a transient association of two or more molecules (e.g., reception, signal transduction, enzyme catalysis). It is anticipated that these findings will advance the development of devices with nanopore-based sensors for chemical and biological applications.

Mechanism of KCl enhancement in detection of nonionic polymers by nanopore sensors.

The mechanisms of KCl-induced enhancement in identification of individual molecules of poly(ethylene glycol) using solitary alpha-hemolysin nanoscale pores are described. The interaction of single molecules with the nanopore causes changes in the ionic current flowing through the pore. We show that the on-rate constant of the process is several hundred times larger and that the off-rate is several hundred times smaller in 4 M KCl than in 1 M KCl. These shifts dramatically improve detection and make single molecule identification feasible. KCl also changes the solubility of poly(ethylene glycol) by the same order of magnitude as it changes the rate constants. In addition, the polymer-nanopore interaction is determined to be a strong non-monotonic function of voltage, indicating that the flexible, nonionic poly(ethylene glycol) acts as a charged molecule. Therefore, salting-out and Coulombic interactions are responsible for the KCl-induced enhancement. These results will advance the development of devices with sensor elements based on single nanopores.