Nanoconjugates of a calixresorcinarene derivative with methoxy poly(ethylene glycol) fragments for drug encapsulation

© 2018 Ermakova et al. In order to obtain a non-toxic amphiphilic calixresorcinarene capable to form nanoconjugates for drug encapsulation, tetraundecylcalixresorcinarene functionalized by methoxy poly(ethylene glycol) chains has been synthesized. The macrocycle obtained is characterized by low hemotoxicity. In aqueous solution it forms nanoassociates that are able to encapsulate organic substrates of different hydrophobicity, including drugs (doxorubicin, naproxen, ibuprofen, quercetin). The micelles of the macrocycle slowed down the release of the hydrophilic substrates in vitro. In physiological sodium chloride solution and phosphate-buffered saline, the micelles of the macrocycle acquire thermoresponsive properties and exhibit a temperature-controlled release of doxorubicin in vitro. The combination of the low toxicity and the encapsulation properties of the obtained calixresorcinarene-mPEG conjugate shows promising potential for the use as a supramolecular drug-delivery system

ESR study of spin adducts of the direct electrocatalytic decomposition of light aliphatic alcohols in a polymer electrolyte fuel cell

Spin adducts of methanol and ethanol electrocatalytic oxidation were detected by the spin trap method using a tiny H2/O2 fuel cell (FC) designed for ESR in situ with a Nafion/Pt membrane electrode assembly. Spin adducts of intermediates of the direct electrooxidation of ethanol, which have not been observed earlier, were obtained by the variation of oxidation conditions, in particular, the FC potential. The work of the FC was controlled by monitoring the diagnostic curves potential3-current density, power density3-current density, and efficiency-power density. © 2010 Springer Science+Business Media, Inc

Selective synthesis of nanosized palladium phosphides from white phosphorus

The reaction of white phosphorus with the palladium(0) complex [Pd 2(dba)3] (dba is dibenzylideneacetone) leads to stable associates [Pd(P4)]n. The coordination polymer obtained is stabilized in a solid state via the formation of nanosized palladium phosphides Pd3P2 and Pd6P with average particle sizes of 140 and 65 nm, respectively. © 2011 Mendeleev Communications. All rights reserved

Impact of polyelectrolyte coating in fluorescent response of Eu(III)-containing nanoparticles on small chelating anions including nucleotides

© 2014 Elsevier B.V. The present work introduces a novel route to sense the permeability of the polyelectrolyte layer deposited onto luminescent core. The use of ternary Eu(III) complexes as the luminescent core enables to detect the permeability of the polyelectrolyte layers through the change of the Eu(III)-centered luminescence. The chelating anions, such as adenosine phosphates, glutamic acid and ethylenediaminetetraacetic acid disodium salt were used as substrates. The origin of the fluorescent response is the complex formation of the substrates with the Eu(III) complexes, which is greatly affected by the equilibrium concentration of the substrates at the surface of the core. The latter in turn is influenced by the permeability of the polyelectrolyte layer. The obtained results highlight the impact of the nature of the exterior layer in the penetration of the substrates through the negatively and positively charged polyelectrolyte layers

Supramolecular strategy to construct quantum dot-based sensors for detection of paraoxon

© 2018 Elsevier B.V. The development of advanced tools for sensing specific materials remains an ongoing challenge. Detailed below is a new quantum dot (QD)-based sensor via supramolecular interactions, demonstrating a novel simplicity of design to obtain sensitive QDs while avoiding their covalent cross-linking. A simple label-free and turn-off method for the detection of paraoxon and its degradation products in aqueous media was proposed by using the fluorescent QD/surfactant/cyclodextrin supramolecular system. This nanocomposite was prepared from 3-mercaptopropionic acid-capped CdTe QDs coated with cetyltrimethylammonium bromide (CTAB) through electrostatic self-assembly. Further nanocomposite modification by β-cyclodextrin (β-CD), thanks to hydrophobic interaction between cetyl tails of surfactants and inner cavity of macrocycle contributed to an increase in emission intensity and stability in aqueous solution. The strong fluorescence of CdTe/CTAB/β-CD nanocomposite can be effectively quenched by the addition of paraoxon due to the host–guest complexation between β-CD cavity and paraoxon degradation product. The functionality of the paraoxon sensor was also tested with blood samples of paraoxon-poisoned rats (1/2 × LD50). These fluorescent nanocomposites were obtained by using the simple supramolecular method to coat QDs with surfactant–cyclodextrin shells. This coating strategy potentially offers common method for the functionalization of QDs and avoids time-consuming synthesis procedures

The supramolecular approach to the phase transfer of carboxylic calixresorcinarene-capped silver nanoparticles

© 2017 Elsevier B.V.The octacarboxylic derivative of tetrapentylcalix[4]resorcinarene (1) was used as stabilizer for preparation of silver nanoparticles (AgNPs) hydrosol. The calixresorcinarene-capped nanoparticles Ag@1 are stably dispersed in an aqueous colloid solution and have an average diameter of 4–6 nm (TEM). The interaction of the macrocycle 1, possessed the receptor properties, with the cationic surfactant cetyltrimetylammonium bromide (CTAB) leads to the hydrophobization of AgNPs hydrosol. It was shown, that macrocycle 1 in its individual solution forms the hydrophobic associate with 8 mol of CTAB (1H NMR, 2D NOESY). Various and complicated influence of CTAB/macrocycle molar ratio on the hydrophobization of AgNPs and their transfer into organic phase was demonstrated. The initial Ag@1 and modified Ag@1-CTAB were characterized by UV-vis and FTIR spectroscopy, DLS, and TG/DSC methods It was shown that the efficiency of water/organic phase transfer depends on the macrocycle/surfactant molar ratio. The presented supramolecular approach can be useful to form the ordered nanostructures through supramolecular modification and self-organization of hybrid metal nanoparticles

Luminescent silica nanoparticles for sensing acetylcholinesterase-catalyzed hydrolysis of acetylcholine

© 2015 Elsevier B.V. This work highlights the H-function of Tb(III)-doped silica nanoparticles in aqueous solutions of acetic acid as a route to sense acetylcholinesterase-catalyzed hydrolysis of acetylcholine (ACh). The H-function results from H+-induced quenching of Tb(III)-centered luminescence due to protonation of Tb(III) complexes located close to silica/water interface. The H-function can be turned on/switched off by the concentration of complexes within core or nanoparticle shell zones, by the silica surface decoration and adsorption of both organic and inorganic cations on silica surface. Results indicate the optimal synthetic procedure for making nanoparticles capable of sensing acetic acid produced by enzymatic hydrolysis of acetylcholine. The H-function of nanoparticles was determined at various concentrations of ACh and AChE. The measurements show experimental conditions for fitting the H-function to Michaelis-Menten kinetics. Results confirm that reliable fluorescent monitoring AChE-catalyzed hydrolysis of ACh is possible through the H-function properties of Tb(III)-doped silica nanoparticles

Calixresorcinarene-capped silver nanoparticles as new supramolecular hybrid nanocontainers

© 2017 The synthesis of small (2–3 nm) silver nanoparticles in the presence of new amidoaminocarboxylic tetrapentylcalix[4]resorcinarene and the binding of the antitumor drug Doxorubicin by a macrocycle in solution and on the surface of nanoparticles are described

Supramolecular nanoscale systems based on amphiphilic tetramethylensulfonatocalix[4]resorcinarenes and cationic polyelectrolyte with controlled guest molecule binding

© 2016 Informa UK Limited, trading as Taylor & Francis GroupThe water-soluble tetramethylensulfonatocalix[4]resorcinarene with methyl (C1) and pentyl (C5) substitutes on the lower rim forms colloid nanoscale aggregates with poly(diallyldimethylammonium chloride) (PDDA) in aqueous solutions. The size and stability of nanoparticles depend on concentrations of the components and their ratio in the ‘calixarene-polymer’ system. Ternary supramolecular complexes «polymer–macrocycle–guest molecule L-tryptophan (Trp) in conditions of spontaneous pH (3.80 and 4.78 for C1-PDDA and C5-PDDA systems, respectively) in an aqueous solution and in phosphate buffer (pH 7) were investigated by fluorescence method. The addition of the third component – PDDA – to the «non-aggregated C1–Trp» associates leads to the release of Trp in all studied conditions. The possibility of the «binding–release» process of L-tryptophan in «C5–Trp» associates after PDDA addition in the ternary complex is achieved and controlled by the structure of the macrocyclic self-associates and pH conditions

One-step synthesis of gold colloids using amidoaminocalix[4]resorcinarenes as reducing and stabilizing agents. Investigation of naproxen binding

© 2017 Elsevier B.V.Amido(dimethylamino) calix[4]resorcinarenes with different substituents on the lower rim (-CH3 (С1), −C5H11 (C5), −C11H23 (C11)) both as reducing and stabilizing agent in an aqueous solution were used for the fabrication of stable gold colloids. Gold colloids are characterized by spectrophotometry, FTIR − spectroscopy, transmission electron microscopy, dynamic light scattering. It is found that increase of the macrocycle's concentration towards HAuCl4 concentration during the synthesis leads to the decrease in the size of formed particles. It is shown that the size of gold nanoparticles (AuNPs) decreases with the increase of the hydrophobicity of the substituents on the macrocycles lower rim (C1@Au − 4–14 nm, C5@Au - 10–11 nm, C11@Au − 7–8 nm). The monolayer packing of the macrocycle molecules on the surface of the metal particle for C1@Au and bilayer − for C5@Au and C11@Au, providing both the stabilization of AuNPs and their solubility in water, are proposed. Temperature and pH variation during the synthesis showed that the optimal synthesis conditions for all kinds of particles C1@Au, C5@Au, C11@Au are spontaneous installed during the synthesis pH (for C1@Au − pH 8.10, C5@Au − pH 8.56, C11@Au − pH 8.63) and the synthesis temperature of the 25 °C. High binding fraction of drug substrate naproxen on the surface of AuNPs modified by C5 and C11 macrocyclic aggregates due to the ordering of the macrocycles on the particle surface and enhancing their receptor ability towards naproxen is defined by fluorescence method