Search

The advances of iron based magnetic nanoparticles are extensively increasing due to the number of sources related to the synthesis process, the control on the particle dispersion and the interactions of ferrofluids that can be provide with different surface modifications. The wide range of uses granted to them are based on the physical, chemical stability and interaction properties in the different yields of material science. In this work, ferromagnetic iron carbide@iron oxide core@shell nanoparticles were synthesized with hydrophobic nature. Water dispersity was controlled by modifying the surface with a synthesized molecule of oleic acid with ethylenediamine by bioconjugation reaction obtaining a conjugated amide-amine modified oleic acid coating 6 nm magnetic nanoparticles with the capacity of being water dispersable. The synthesized nanoparticles, with modified organic acid and surface modified nanoparticle were characterized by TEM, DLS, zeta potential, mass spectrometry, FTIR and NMR.

Debido a la importancia de los aniones y diversas sales en la biología y el medio ambiente, existe un gran interés por el reconocimiento molecular de estas especies. Al respecto, la técnica de fluorescencia es una buena herramienta para su detección y cuantificación. En este trabajo, se reporta la síntesis y caracterización de dos nuevos receptores bis-tiourea, Rec1 y Rec2, y los estudios de reconocimiento molecular en DMSO de estos sistemas y los aniones F-, Cl-, Br-, I-, NO3-, CH3COO-, HSO4- y H2PO4-, como sales de tetraalquilamonio. Adicionalmente, se estudiaron las sales de metales alcalinos NaF, NaCl, KCl, LiCl, KI, Na2HPO4 y Na2SO4 en DMSO:Agua (95:5 v/v). Todos estos estudios se realizaron mediante la técnica de fluorescencia en microplaca. Ambos receptores mostraron mejores afinidades y respuestas espectrales con las sales de aniones básicos. A partir de la respuesta en fluorescencia de Rec1 y Rec2, se obtuvieron los límites de cuantificación y de detección para las sales NaCH3COO, Na2SO4, Na2HPO4 y NaF, siendo esta última cuantificable en concentraciones similaresa las establecidas en las normas oficiales mexicanas para el agua potable. Por tal razón, la cuantificación del fluoruro por Rec1 y Rec2 podría ser aplicada en muestras acuosas y de alimentos.

Two bis-urea type receptors were synthesized containing a polyether bridge and two 4-nitrophenyl groups as chromogenic units, R1 and R2. Molecular recognition studies of receptors towards different tetraalkylammonium and alkali metal salts were carried out in DMSO by UV-Vis and 1H-NMR spectroscopy. The receptors were found to have high affinity for diverse anions and ion-pairs, showing the highest affinities towards the tetramethylammonium and sodium salts. The cation binding ability of the receptors was evidenced by means 1H NMR, mass spectrometric ESI+ studies and the crystal structures of some precursors. Additionally, the molecular modelling at the DFT level of the tetramethylammonium acetate complexes illustrates the potential ion-pair binding ability of the receptors: the anion is recognized through strong hydrogen bonds from the NH─ groups from the two urea sites, while the cation is bound by a combination of cation─π, C-H···O and C-H···π interactions.

A 20-membered dioxadiaza-calix[4]arene analog ( 1 ) was combined with a series of inorganic acids to explore the anion-inclusion properties of the corresponding ammonium dication [ 1-H 2 ] 2+ . The neutral calix[4]arene analog 1 and six salts of the receptor in the mono- or diprotonated form, [ 1-H 2 ]Cl 2 ( 2 ), [ 1-H 2 ]Br 2 ( 3 ), [ 1-H 2 ][MeOSO 3 ] 2 ( 4 ), [ 1-H 2 ][NO 3 ] 2 ( 5 ), [ 1-H 2 ][ClO 4 ] 2 ( 6 ), and [ 1-H ][ClO 4 ] ( 6b ), were structurally characterized by single-crystal X-ray diffraction analysis, which enabled a detailed comparative analysis of the non-covalent interactions. The structural comparison showed that the different anions induce conformational changes of the macrocyclic structure, but only NO 3 − gave a true inclusion complex. Additionally, the tetramethylammonium derivative of 1 , [ 1-Me 4 ]I 2 ( 7 ), was prepared and structurally characterized. 1 H NMR titration studies of [ 1-H 2 ] 2+ in an aqueous–polar solvent mixture (H 2 O/MeOH, 9:1 v/v, pH 5.5) with a series of organic and inorganic anions gave association constants varying from 1.4 to 84.6 M −1 .

In this work, we report on the synthesis of two new mono-alkylated tetrandrine derivatives with acridine and anthracene units, MAcT and MAnT. The compounds were fully characterized by physicochemical techniques and single-crystal X-ray diffraction analysis. In addition, both derivatives were studied as nucleotide receptors and double-stranded DNA binders in aqueous phosphate buffer at pH = 7.2 using UV–vis and fluorescence spectroscopy. According to the molecular recognition studies, MAcT and MAnT exhibit high affinity (K ∼ 105 M−1) and selectivity for ds-DNA, presumably in an intercalation mode. Finally, the anti-proliferative effects of the tetrandrine derivatives on different cancer cell lines were explored, revealing promising activities. Particularly, the mono-anthracene tetrandrine derivative MAnT showed an IC50 of 2.74 μg/mL on the HeLa cervical cancer cell line, representing a value 3.3 times smaller than that obtained for unsubstituted tetrandrine. Examination of the cytotoxic effects on the HeLa cell line by inverted microscopy suggests that the cell death mechanism consists basically in apoptosis. The molecular modelling of three ds-DNA-MAcT complexes, suggested that the macrocycles may use an intercalation binding mode towards DNA. MAcT is predicted to bind into the major groove of the ds-DNA providing non-covalent interactions such as electrostatic, van der Waals and hydrophobic interactions that lead to selectivity. Overall experimental data supports the mode of action of MAnT and MAcT as cytotoxic compounds against cancer cell lines via a DNA interaction mechanism.

National Council of Science and Technology (CONACyT) [INFR-226208-2014, INFR-255791-2015]; CONACYT

A series of oxaazacyclophanes and oxaazacalix[4]arene analogues with 18-, 20- and 22-membered rings have been synthesized from diamine and dialdehyde building blocks and structurally characterized by spectroscopic methods. One diamine precursor and four macrocycles have additionally been analysed by single-crystal X-ray diffraction. Two of the oxaazacalix[4]arene analogues were employed for metal ion complexation studies based on UV/Vis absorption spectroscopy, showing both compounds to be able to form complexes with Cu2+ and Zn2+.

Water soluble dicationic cyclophane-type macrocycles bearing two anthraquinone (1) or two acridine groups (2) have been prepared by chemical modification of S,S-(+)-tetrandrine. Complexation of nucleotide anions (mono- di- and triphosphates) and D/L phenylalanine by tetrandrine derivatives has been studied by UV-Visible and fluorescence titrations in water. Association of nucleotides to semi-synthetic hosts 1 and 2 increases with increasing guest charge in the series AMP2 −