Tatiana V. Shishkanova

Cytosine substituted calix[4]pyrroles: Neutral receptors for 5′-guanosine monophosphate

The synthesis and characterization of two cytosine-substituted calix[4]pyrrole conjugates, bearing the appended cytosine attached at either a β- or meso-pyrrolic position, is described. These systems were tested as nucleotide-selective carriers and as active components of nucleotide-sensing ion-selective electrodes at pH 6.6. Studies of carrier selectivity were made using a Pressman-type model membrane system consisting of an initial pH 6.0 aqueous phase, an intervening dichloromethane barrier containing the calix[4]pyrrole conjugate, and a receiving basic aqueous phase. Good selectivity for the Watson–Crick complementary nucleotide, 5′-guanosine monophosphate (5′-GMP), was seen in the case of the meso-linked conjugate with the relative rates of through-membrane transport being 7.7:4.1:1 for 5′-GMP, 5′-AMP, and 5′-CMP, respectively. By contrast, the β-substituted conjugate, while showing a selectivity for 5′-GMP that was enhanced relative to unsubstituted calix[4]pyrrole, was found to transport 5′-CMP roughly 4.5 times more quickly than 5′-GMP. Higher selectivities were also found for 5′-CMP when both the β- and meso-substituted conjugates were incorporated into polyvinyl chloride membranes and tested as ion selective electrodes at pH 6.6, whereas near-equal selectivities were observed for 5′-CMP and 5′-GMP in the case of unsubstituted calix[4]pyrroles. These seemingly disparate results are consistent with a picture wherein the meso-substituted cytosine calix[4]pyrrole conjugate, but not its β-linked congener, is capable of acting as a ditopic receptor, binding concurrently both the phosphate anion and nucleobase portions of 5′-GMP to the calixpyrrole core and cytosine “tails” of the molecule, respectively, with the effect of this binding being most apparent under the conditions of the transport experiments.

Potentiometric anion response of poly(5,15-bis(2-aminophenyl)porphyrin) electropolymerized electrodes

Abstract The preparation of novel poly(porphyrin) film based on the 5,15-bis(2-aminophenyl) porphyrin from aqueous solutions with and without porphyrin core modification is reported. Anion-selective binding for inorganic ions was found to be in the order: Sal − − 3 COO − ≈ClO − 4 2− 4 ≈Cl − − − 3 − and SO 2− 4 − − − 4 3 COO − − 3 − − − respectively, for the free base film (not complexed) and the poly(porphyrin) film complexed with metal. The potentiometric selectivity patterns reflect different response mechanisms of the polymerized electrode: 1. ion-exchange for not complexed film, and 2. selective axial ligation between metal center and certain anion for poly(porphyrin) film complexed with metal.

Optimization of the thickness of a conducting polymer, polyaniline, deposited on the surface of poly(vinyl chloride) membranes: A new way to improve their potentiometric response

Repeated depositions of polyaniline (PANI) have been used to control the thickness of the polymeric film deposited on poly(vinyl chloride) (PVC) membrane surface. The oxidation of aniline was carried out in a dispersion mode, i.e. in the presence of poly(N-vinylpyrrolidone) (PVP). Two kinds of PVC were used for this purpose: a non-plasticized PVC for the study of PANI deposition and PVC, plasticized with nitrophenyl octyl ether (NPOE), as a prototype of a liquid membrane electrode. The results of UV-visible and FTIR spectroscopies and electron microscopy showed that (1) the film thickness increased by about equal increments of approximately 40 nm after each polymerization, and (2) the interface with PVC was constituted by PANI film and adhering PANI-PVP colloidal particles. The various thicknesses of the deposited PANI films affected the potentiometric response of the NPOE/PVC membrane with and without an anion-exchanger. The potentiometric anionic response was observed with a minimal thickness of PANI film on the blank NPOE/PVC membrane. Sensitivity of the PANI film to pH occurred only with a blank NPOE/PVC membrane coated with a thick polymeric film, while it was strongly suppressed by the presence of a lipophilic anion-exchanger, tridodecylmethylammonium chloride (TDDMACl), in the membrane, regardless of the thickness of the polymer film. The thickness of the PANI film did not affect the anionic selectivity pattern of TDDMACl-based membranes to any great extent, but its presence improved and stabilized their potentiometric characteristics (sensitivity, linear-response range).

Preparation, characterization and analytical application of electropolymerized films

Abstract Conditions for preparation of ion-selective electrodes (ISEs) based on novel electropolymerized films were tested. Polymerized films of substituted anilines, pyrroles and heterocycles were prepared by electrochemical oxidation. Prepared films were characterized by cyclic voltammetry and by Surface Enhanced Raman Scattering (SERS). Film of 3-(1-pyrrolylethylamido)-2,2′-dihydroxy-1,1′-binaphthol exhibits potentiometric response to dicarboxylates and amino acids. Electropolymerized film of 2-amino-4,6-dihydroxypyrimidine shows potentiometric response to ascorbic acid. Detection limits and selectivity coefficients were determined.

Novel Potentiometric Sensor for Determination of Cysteine Based on Substituted Poly(diphenylporphyrins and Metalloporphyrins)

This paper describes the application of an electropolymerized film of poly(bis(2-aminophenyl)-2,8,12,18-tetraethyl-3,7,13, 17-tetramethylporphyrin) and its metalloderivative for determination of amino acids. A remarkable selectivity for cysteine (log KCys/Amino acidspot = 10−2–10−3) has been found. The potentiometric response to sulfur-containing amino acids is discussed and compared with selectivity data for PVC-membranes based on metallotetraphenylporphyrins.

Terahertz split-ring metamaterials as transducers for chemical sensors based on conducting polymers: a feasibility study with sensing of acidic and basic gases using polyaniline chemosensitive layer

AbstractWe report on the first application of terahertz metamaterials acting as transducers for chemical sensors based on conducting polymers. In our feasibility study aimed at sensing of gaseous hydrochloric and ammonia, a two-dimensional sensor metamaterial consisting of an array of split-ring resonators on the surface of undoped silicon wafer was prepared. The surface of the resonator was coated with a 150-μm layer of polyaniline. Binding of hydrogen chloride to polyaniline leads to distinct changes in the resonance frequency of the metamaterial. Measurements can be performed both in the reflection and transmission mode. A numerical simulation of the response revealed an increase of both the real and the imaginary components of the dielectric function of the polyaniline film. These changes are attributed to the transition from emaraldine base to emeraldine salt. The results demonstrate a new approach for formation of highly sensitive transducers for chemical sensors. ᅟ

Synthesis and deposition of a Tröger’s base polymer on the electrode surface for potentiometric detection of a neuroblastoma tumor marker metabolite

The development of novel diagnostic tools is a primary goal in bioanalytical chemistry. Here we report the synthesis of Trögers base functionalized with amino- and coumarin-units designed as a monomeric unit for the development of an electrochemical cancer sensor. The synthesized receptor was deposited onto a conducting support using electrochemical polymerization, characterized spectroscopically and tested potentiometrically towards metabolites used as tumor markers of neuroblastoma.

Molecular recognition of amino acid esters in liquid polymeric membrane ion-selective electrodes

Abstract The application of binaphthol derivatives 6′-tert-butyl-3-[2-(2-hydroxyethoxy)-ethoxymethyl]-[1,1′-binaphthalenyl]-2,2′-diol (1) and 2-(2,2′-dimethoxy-1,1′-binaphthalenyl-3-ylmethoxy)phenol (2) as novel multitopic receptors for amino acid esters within plasticized PVC membranes is described. Potentiometric experiments have shown that the recognition behavior of amino acid esters was significantly controlled by intermolecular interactions between the receptor and the NH3+ group and the residual “R” group on the α-carbon of the target substrate (amino acid ester). In addition, a 1 H NMR investigation served to (i) confirm the potentiometric data, concerning the key binding modes for molecular recognition of amino acid esters by binaphthol receptors, (ii) determine the stoichiometry of the complex binaphthol derivative — amino acid ester (1:1 and 1:2) and (iii) evaluate corresponding binding constants for AlaOMe.

Influence of polyaniline on the potentiometric determination of risedronate with ion-selective membranes

A novel kind of potentiometric sensor for the determination of risedronate in pharmaceutical products is proposed. This potentiometric sensor is comprised of a poly(vinyl chloride) (PVC) membrane based on an anion-exchanger, tridodecylmethylammonium chloride (TDDMACl), and coated with a polyaniline (PANI) layer. The potentiometric response towards a highly hydrated risedronate species was strongly promoted by the presence of the PANI layer. In contrast to uncoated membranes, the PANI-coated membrane exhibited a sensitivity of −39.9 ± 0.9 mV decade−1 and the detection limit reached 0.45 mg mL−1. The results of the potentiometric analysis of risedronate agreed with those obtained with a validated chromatographic method. The TDDMACl-based membrane coated with the PANI layer differentiated 0.94 wt % and 3.44 wt % of a specific contaminant in 1.6 mg mL−1 risedronate.

Influence of surface properties on the deposition of a polyaniline film and detection of tumor markers

The deposition of polyaniline (PANI) onto the surface of plasticized poly(vinyl chloride) (PVC) membranes requires optimizing the membrane composition. Controlling the ratio between the plasticizer and PVC enables the hydrophilic surface to be prepared and a homogeneous PANI film to be deposited through chemical polymerization. Our studies showed that such modified PVC membranes can be used for the potentiometric detection of three tumor markers (TMs) that are metabolites of catecholamines and serves as a screening test for neuroblastoma. Furthermore, the interactions of PANI with these TMs were proved by a capillary electrophoresis method in which a capillary covered with PANI was used.