D. N. Shurpik

Acetylcholinesterase biosensor for inhibitor measurements based on glassy carbon electrode modified with carbon black and pillar[5]arene

New acetylcholinesterase (AChE) biosensor based on unsubstituted pillar[5]arene (P[5]A) as electron mediator was developed and successfully used for highly sensitive detection of organophosphate and carbamate pesticides. The AChE from electric eel was immobilized by carbodiimide binding on carbon black (CB) placed on glassy carbon electrode. The working potential of 200mV was obtained in chronoamperometric mode with the measurement time of 180 s providing best inter-biosensors precision of the results. The AChE biosensor developed made it possible to detect 1×10(-11)-1×10(-6) M of malaoxon, 1×10(-8)-7×10(-6) M of methyl-paraoxon, 1×10(-10)-2×10(-6) M of carbofuran and 7×10(-9)-1×10(-5) M of aldicarb with 10 min incubation. The limits of detection were 4×10(-12), 5×10(-9), 2×10(-11) and 6×10(-10) M, respectively. The AChE biosensor was tested in the analysis of pesticide residuals in spiked samples of peanut and beetroot. The protecting effect of P[5]A derivative bearing quaternary ammonia groups on malaoxon inhibition was shown.

Selective stepwise oxidation of 1,4-decamethoxypillar[5]arene

For the first time, the 1H and 13C{1H} NMR data were classified and analyzed for the pillar[5]arenes with one, two, three and five 1,4-benzoquinone fragments obtained in good yields. The empirical relationships established make it possible to define the relative position of the quinone and aryl fragments to each other in the oxidation products of any pillar[n]arenes.

An electrochemical aptasensor for cytochrome C, based on pillar[5]arene modified with Neutral Red

An electrochemical aptasensor is developed for the highly sensitive determination of cytochrome C, using a change in the redox current of Neutral Red covalently bound to terminal carboxyl groups of decasubstituted pillar[5]arene as a signal. The inclusion of the analyte into the complex with an aptamer reduces peaks of redox current of the dye through the dissociation of electron transfer chain in the surface layer. The aptasensor enables the determination of 1 nM to 1.0 mM of cytochrome C in the presence of 1000-fold excesses of albumin, polyethylene glycol, and lysozyme as models of interfering components in biological fluids.

Synthesis of benzothiazine sulfonamides via heteroatomic Diels–Alder reaction of para-fluoro-N-sulfinylaniline with bicyclo[2.2.1]heptenes

Reaction of 4-fluoro-N-sulfinylaniline with norbornene and norbornadiene has afforded the Diels–Alder adducts of benzothiazine structure that have been oxidized into the corresponding benzothiazine sulfonamides. Structure of the obtained compounds and stereochemistry of the diene addition and epoxidation of norbornene olefin bonds have established by means of X-ray diffraction method.

Synthesis and properties of chiral nanoparticles based on (pS)- and (pR)-decasubstituted pillar[5]arenes containing secondary amide fragments

Employing induced asymmetric synthesis, new decasubstituted pillar[5]arenes containing (R)-(+)- or (S)-(−)-1-phenylethane-1-acetamide fragments have been obtained and characterized. Using NTA and TEM, and circular dichroism spectroscopy, it was shown that the amidopillar[5]arenes synthesized form spherical chiral nanoscale aggregates in CHCl3. During heating, both positive and negative Cotton effects corresponding to nanoparticles in CHCl3 reversibly decrease. Keeping the nanoparticles at room temperature results in a decrease in their size and intensification of the Cotton effect.

Electrochemical DNA Sensor Based on Carbon Black—Poly(Neutral Red) Composite for Detection of Oxidative DNA Damage

Voltammetric DNA sensor has been proposed on the platform of glassy carbon electrode covered with carbon black with adsorbed pillar[5]arene molecules. Electropolymerization of Neutral Red performed in the presence of native or oxidatively damaged DNA resulted in formation of hybrid material which activity depended on the DNA conditions. The assembling of the surface layer was confirmed by scanning electron microscopy and electrochemical impedance spectroscopy. The influence of DNA and pillar[5]arene on redox activity of polymeric dye was investigated and a significant increase of the peak currents was found for DNA damaged by reactive oxygen species generated by Cu2+/H2O2 mixture. Pillar[5]arene improves the electron exchange conditions and increases the response and its reproducibility. The applicability of the DNA sensor developed was shown on the example of ascorbic acid as antioxidant. It decreases the current in the concentration range from 1.0 μM to 1.0 mM. The possibility to detect antioxidant activity was qualitatively confirmed by testing tera infusion. The DNA sensor developed can find application in testing of carcinogenic species and searching for new antitumor drugs.

Tetracarboxylic acids on a thiacalixarene scaffold: synthesis and binding of dopamine hydrochloride

For the first time thiacalix[4]arene derivatives in 1,3-alternate conformation simultaneously containing amide, carboxyl and hydroxyl groups capable of forming 1 : 1 stoichiometry complexes with dopamine hydrochloride were obtained. The efficiency of dopamine hydrochloride binding was evaluated by a number of spectral methods. Using the methods of fluorescent, UV-Vis and NMR spectroscopy, the mechanism of interaction of the synthesized macrocycles with dopamine has been studied. It was shown that quenching of dopamine fluorescence by the studied macrocycles is carried out through a static mechanism.

Electrochemical Determination of Malathion on an Acetylcholinesterase-Modified Glassy Carbon Electrode

ABSTRACT An acetylcholinesterase biosensor based on glassy carbon electrode modified with carbon black and pillar[5]arene was used for the determination of malathion after its preliminary oxidation. The contributions of enzyme immobilization and oxidation conditions to the improvement of analytical characteristics of the biosensor were considered and quantified. In optimal conditions, the acetylcholinesterase biosensor allows the determination of 40 pM of malathion with 10 min of incubation and 15 pM with 30 min of incubation. The sensitivity of immobilized enzyme was found to be higher than that the free enzyme due to sorbtional accumulation in the modifier layer. Incomplete oxidation of malathion decreased the sensitivity of the assay. The developed acetylcholinesterase biosensor was validated for the determination of malathion residues in grapes, wine, and peanuts. The recoveries calculated against a high-performance liquid chromatography assay were between 80 and 120% due to possible matrix effects and the simplified extraction protocols.

Supramolecular polymer based on aminated monosubstituted pillar[5]arene

The interaction of nonamethoxypillar[5]arene containing an ester fragment with a series of di- and triamines has yielded novel macrocyclic amide derivatives of pillar[5]arene. The data of NOESY 1H–1H and DOSY NMR spectroscopy, dynamic light scattering, and transmission electron microscopy have revealed that nonamethoxypillar[5]arene containing diethylenediaminoamide moiety can form a network supramolecular polymer with average pores size of 100 nm.

Synthesis of cyclic sulfonamides by reaction of N-sulfinyl-3-(trifluoromethyl)aniline with norbornenes

N-Sulfinyl-3-(trifluoromethyl)aniline reacted with bicyclo[2.2.1]hept-2-ene and bicyclo[2.2.1]-hepta-2,5-diene to give the corresponding Diels‒Alder adducts which were oxidized to 8-trifluoromethyl-2,3,4,4a,6,10b-hexahydro-5λ6-1,4-methanodibenzo[c,e][1,2]thiazine-5,5(1H)-diones. The cycloaddition occurred predominantly with participation of the S=N–C1=C6 fragment of N-sulfinyl-3-(trifluoromethyl)aniline and exclusively at the endo side of bicyclo[2.2.1]heptenes.