Electrochemical enzyme biosensors are extensively utilized in clinical analysis and environmental monitoring, yet achieving effective enzyme immobilization while maintaining high activity remains a challenge. In this work, we developed a flow-through enzyme biosensor system using a 3D-printed flow-through electrochemical cell fabricated from commercially available poly (lactic acid). After modification with thiacalixarene-functionalized oligo (lactic acids) (OLAs), the material enabled efficient immobilization of uricase on the inner surface of a replaceable reactor of the cell. Swelling and hydrolytic stability of OLAs in cone, partial cone, and 1,3-alternate conformations were studied, with 1,3-alernate conformation demonstrating superior stability and enzyme immobilization performance. The use of OLAs enhanced immobilization efficiency by over 30% and protected the reactor from swelling, hydrolytic degradation, and enzyme loss. The biosensor was validated for amperometric uric acid determination, with a screen-printed carbon electrode modified with carbon black and Prussian Blue. This modification reduced the cathodic potential for uric acid detection to –0.05 V. The biosensor exhibited a linear detection range of 10 nM to 30 μM with a detection limit of 7 nM, and it performed effectively in artificial urine and synthetic blood plasma. The novel cell design, featuring easy assembly and low-cost replaceable parts, makes this biosensor a promising candidate for routine clinical analysis and other practical applications.

Thermal treatment of linear dipeptides in solid state makes it possible to obtain their cyclic analogues in high yield and without additional expenses. At the same time, such reactions occurring under the conditions of crystal lattice restrictions with the participation of molecules in the zwitterionic form have not been sufficiently studied. In this work, the cyclization reaction of the L-leucyl-L-valine dipeptide in the crystalline phase upon heating was studied. Using isoconversion kinetics approaches, a kinetic model describing this process was found, and kinetic parameters were calculated, including activation energy, Arrhenius factor, and reaction order. The enantiomeric purity of the resulting cyclic product was assessed. The self-assembly of linear and cyclic dipeptides on a solid substrate was studied. The results of the study will be useful in determining mechanisms of the cyclization reactions of dipeptides in the solid state, and can also be used in the development of effective and cost-efficient methods for the production of cyclic dipeptides.

Министерство науки и высшего образования Российской Федерации Российское химическое общество им.Д.И.Менделеева Секция по химической термодинамике и термохимии Научного совета РАН по физической химии Сибирское Отделение Российской Академии Наук Институт неорганической химии им.А.В.Николаева СО РАН

В работе изучено влияние размера макроцикла нативных циклодекстринов и их гидратации на инкапсуляцию ритонавира в условиях механического перемалывания. Разработан способ оценки степени включения ритонавира циклодекстринами, используя кристаллизацию несвязанного «гостя» в продуктах перемалывания при обработке парами воды. Установлено, что ритонавир практически полностью связывается безводными α-, β- и γ-циклодекстринами с образованием соединений включения. Для гидратов циклодекстринов соотношение структура-свойство для связывания ритонавира в зависимости от размера макроцикла «хозяина» является нелинейным. Ритонавир полностью связывается насыщенным гидратом β-циклодекстрина и промежуточными гидратом γ-циклодекстрина. Степень включения ритонавира насыщенными гидратами α-циклодекстрина и особенно γ-циклодекстрина невелика, что обусловлено конкуренцией этого гостя с водой.

We study how the size of the macrocycle of native cyclodextrins and their hydration influence the inclusion of ritonavir under mechanical grinding conditions. A procedure is proposed to estimate the degree of inclusion of ritonavir by cyclodextrins using the crystallization of the unincluded guest in the grinding products at the water vapor treatment. Ritonavir is almost completely included by anhydrous α-, β-, and γ-cyclodextrins, resulting in the formation of inclusion compounds. The structure–property relationship between ritonavir inclusion in cyclodextrin hydrates and the size of the host macrocycle is nonlinear. Ritonavir is completely included by saturated β-cyclodextrin hydrate and intermediate γ-cyclodextrin hydrates. The degree of ritonavir inclusion by saturated hydrates of α-cyclodextrin and particularly of γ-cyclodextrin is small due to the competition of this guest with water.

An efficient method to prepare polymorphs (including the unknown previously) is proposed for tert -butylthiacalix[4]arene tetrasubstituted with ethylcarboxymethyloxy groups at the lower rim by saturating this host and its inclusion compounds by solvent vapors. By means of this method and by heating this calixarene capable of the enantiotropic transition, it is shown that mutual transformations of polymorphs into each other can be controlled. Polymorphs and intermediate saturation products are characterized by a combination of thermogravimetry, differential scanning calorimetry, and powder X-ray diffraction. To reveal factors promoting polymorphism, the structures of two inclusion compounds and one of the polymorphs of calixarene studied are determined by single crystal X-ray diffraction.

Для тетразамещенного по нижнему ободу этилкарбоксиметилокси группами трет-бутилтиакаликс[4]арена предложен эффективный способ приготовления полиморфов, в том числе ранее неизвестного, путем насыщения парами растворителей этого хозяина и его соединений включения. С применением этого способа и нагрева для этого каликсарена, способного к энантиотропному переходу, показана возможность управления взаимными превращениями полиморфов друг в друга. Полиморфы и промежуточные продукты насыщения были охарактеризованы совмещенным методом термогравиметрии и дифференциальной сканирующей калориметрии, порошковой рентгеновской дифрактометрии. Для выявления факторов, способствующих полиморфизму, методом рентгеноструктурного анализа определена структура двух соединений включения и одного из полиморфов изученного каликсарена.

Bis-sulfophenylamino derivative of phenothiazine has been synthesized by the reaction of 4-aminobenzenesulfonic acid with phenothiazin-5-ium tetraiodide. The obtained water-soluble structural analog of emeraldine tetramers was used as doping agent for emeraldine base. It has been found that 3,7-bis((4-sulfophenyl)amino)phenothiazin-5-ium chloride-doped emeraldine forms monodisperse system in water (439 nm, PDI=0.1) and is more stable than p-toluenesulfonic acid-doped emeraldine (1360 nm, PDI=0.3 in one hour after ultrasonication). Dispersions have been investigated using scanning electron microscopy. Dispersion of 3,7-bis((4-sulfophenyl)amino)phenothiazin-5-ium chloride-doped emeraldine is a two-component nanomaterial: nanofibers (diameter 50 nm) with uniformly distributed 3,7-bis((4-sulfophenyl)amino)phenothiazin-5-ium chloride particles (average size 100 nm).

Oligo−/polylactides functionalized with p-tert-butylthiacalix[4]arenes in three conformations (cone, partial cone, 1,3-alternate) were synthesized by ring-opening polymerization. Conformational isomers of p-tert-butylthiacalix[4]arene tetrapropanolamide derivatives differing in relative position of hydroxyl groups were introduced into reaction with l-lactide in presence of catalytic amounts of tin (II) octoate in DMSO and 1,2-dimethylbenzene. It was shown that oligo−/polyester molecular weight depends on macrocycle's conformation and solvent used for l-lactide ROP. Highest molecular weight was achieved for 1,3-alternate conformation and 1,2-dimethylbenzene, while on the contrary in DMSO higher molecular weight was achieved for cone stereoisomer. Regardless molecular weight of oligo−/polylactides synthesized, 1,3-alternate stereoisomer derivatives are characterized by higher thermal stability, indicating that the relative position of oligo−/polylactides fragments, which are pre-oriented by cyclophane core is the key factor determining thermal stability of oligo−/polylactides synthesized. Modification of polyesters with thiacalixarene fragment bestows them with sorption activity towards rhodamine 6G in contrast to non-modified polylactide.

Silver nanoparticles (AgNPs) are an attractive alternative to plasmonic gold nanoparticles. The relative cheapness and redox stability determine the growing interest of researchers in obtaining selective plasmonic and electrochemical (bio)sensors based on silver nanoparticles. The controlled synthesis of metal nanoparticles of a defined morphology is a nontrivial task, important for such fields as biochemistry, catalysis, biosensors and microelectronics. Cyclophanes are well known for their great receptor properties and are of particular interest in the creation of metal nanoparticles due to a variety of cyclophane 3D structures and unique redox abilities. Silver ion-based supramolecular assemblies are attractive due to the possibility of reduction by “soft” reducing agents as well as being accessible precursors for silver nanoparticles of predefined morphology, which are promising for implementation in plasmonic sensors. For this purpose, the chemistry of cyclophanes offers a whole arsenal of approaches: exocyclic ion coordination, association, stabilization of the growth centers of metal nanoparticles, as well as in reduction of silver ions. Thus, this review presents the recent advances in the synthesis and stabilization of Ag (0) nanoparticles based on self-assembly of associates with Ag (I) ions with the participation of bulk platforms of cyclophanes (resorcin[4]arenes, (thia)calix[n]arenes, pillar[n]arenes).

Electrochemical behavior of new phenothiazine derivative, N-phenyl-3-(phenylimino)-3H-phenothiazin-7-amine (PhTz) and of the product of its electropolymerization has been investigated on glassy carbon electrode using electrochemical techniques. Monomeric PhTz is involved in quasi-reversible electron transfer complicated with adsorption of oxidized form. The transfer coefficient and standard heterogeneous constant were estimated in a wide pH range. In multiple cycling of the potential, the PhTz was oxidized to the polymeric film, which growth was confirmed by electrochemical impedance spectroscopy. Maximal deposition of the product was found for application of the upper potential of 1.3 V. Sulfate and nitrate anions promote electropolymerization whereas chloride ions inhibit the reaction. The reduction of polyPhTz depended on the number of the potential scans because of the increase of diffusional permeability with the number of cycles. A broad pH dependency of the potential, reversibility of the redox reactions and similarity of the behavior of monomeric and polymeric forms of PhTz make them attractive for future application in the assembly of electrochemical (bio)sensors. It was shown on the example of application of appropriately modified electrodes in acid-base and redox titration and in discrimination of native and damaged DNA adsorbed onto the polyPhTz layer based on the changes in the impedance parameters. (C) 2020 Elsevier Ltd. All rights reserved.

Methylene blue and its structural analogs (phenothiazine derivatives) are well known photodynamically and photochemically active agents, which are used in modern medicine, biology, and industry due to their low toxicity, high absorption in the therapeutic window region (600-660 nm). Methylene blue being one of the most studied phenothiazine derivative is employed as an antibacterial agent and also as an antidote to cyanide, carbon monoxide and hydrogen sulfide. Phenothiazin-5-ium tetraiodide is one of the most convenient precursors for the synthesis of structural analogues of methylene blue among the variety of modern synthetic approaches. Nucleophilic addition of aromatic and aliphatic amines to phenothiazin-5-ium tetraiodide can be used to obtain a wide range of 3,7-phenothiazine-5-ium derivatives. The specificities of addition reactions of dialkylamines and aromatic amines to phenothiazin-5-ium tetraiodide are low yields and formation of difficultly separable mixtures of products. It was found that reactions of phenathiazin-5-ium tetraiodide with amines containing secondary and tertiary amino groups lead to oligomerization of phenathiazin-5-ium tetraiodide (3,10-positions). Basicity of tertiary amino group is crucial in oligomerization of phenathiazin-5-ium tetraiodide. It is shown, that triethylamine use as a base allows to synthesize of oligo(3,10)phenothiazines with high yields. According to 1Н, 13C NMR, IR spectroscopy data and MALDI mass-spectrometry data, thereaction product is a mixture of oligomers, consisting mainly of three to four units.

Dispersions of non-toxic compounds characterized by an intense absorbance in the near-IR range find use in photodynamic therapy as effcient antibacterial and anticancer agents. An approach to the preparation of aqueous dispersions of nanoparticles with controlled morphology is described. 3,7-Bis(arylamino)phenothiazin-5-ium derivatives containing the ester and carboxylic groups were synthesized for the first time by the oxidative addition of methyl anthranilate to phenothiazin-5-ium tetraiodide with subsequent hydrolysis of the ester groups. The association with 3-phenylimino-7-phenylaminophenothiazine was studied for the synthesized bis(carboxyl)phenothiazinium derivative. The obtained 1: 1 associate is characterized by the bathochromic shift. The nanoprecipitation of the obtained nanoassociate in a methanol-water system was studied, and the morphology of the prepared dispersions was characterized: 3-phenylimino-7-phenylaminophenothiazine forms nanofiber structures, bis(carboxyl) derivative forms spherical particles, and the two-component associate forms facet-shaped particles

The determination of antibiotics in food is important due to their negative effect on human health related to antimicrobial resistance problem, renal toxicity, and allergic effects. We propose an impedimetric aptasensor for the determination of kanamycin A (KANA), which was assembled on the glassy carbon electrode by the deposition of carbon black in a chitosan matrix followed by carbodiimide binding of aminated aptamer mixed with oligolactide derivative of thiacalix[4]arene in aconeconfiguration. The assembling was monitored by cyclic voltammetry, electrochemical impedance spectroscopy, and scanning electron microscopy. In the presence of the KANA, the charge transfer resistance of the inner interface surprisingly decreased with the analyte concentration within 0.7 and 50 nM (limit of detection 0.3 nM). This was attributed to the partial shielding of the negative charge of the aptamer and of its support, a highly porous 3D structure of the surface layer caused by a macrocyclic core of the carrier. The use of electrostatic assembling in the presence of cationic polyelectrolyte decreased tenfold the detectable concentration of KANA. The aptasensor was successfully tested in the determination of KANA in spiked milk and yogurt with recoveries within 95% and 115%.

Oligolactic acid modified with thiacalixarenes forms nanosized associates with transport proteins and micron-scale aggregates with lysozyme.

A new acetylcholinesterase biosensor has been developed for the determination of anticholinesterase drugs applied for neurodegenerative disease treatment. For this purpose, silver nanosendrites were deposited by potentiostatic electrolysis on a glassy carbon electrode covered with oligolactides cross-linked with p-tert-butylthiacliax[4]arene core in the cone, partial cone, and 1,3-alternate configurations. The roles of macrocycle configuration and electrolysis conditions on the silver depostion were characterized and optimal conditions selected for the subsequent immobilization of acetylcholinesterase. Silver nanoparticles provide higher response at low working potential (0.05 V) due to the electrostatic accumulation of silver ions and prevention of their leaching after reoxidation. The biosensor allows the determination of 10(-12) - 10(-7) M donepezil, berberine, and huperzine A within 20-30 s by the relative decay of the current related to the oxidation of thiocholine formed in enzymatic reaction. The reversible inhibition of immobilized acetylcholinesterase with huperzine A was quantified for the first time. The developed biosensor was employed for the analysis of spiked urine samples.

DNA sensors were assembled by consecutive deposition of thiacalix[4]arenes bearing oligolactic fragments, poly(ethylene imine), and DNA onto the glassy carbon electrode. The assembling of the layers was monitored with scanning electron microscopy, cyclic voltammetry and electrochemical impedance spectroscopy. The configuration of the thiacalix[4]arene core determined self-assembling of the polymeric species to the nano/micro particles with a size of 70–350 nm. Depending on the granulation, the coatings show the accumulation of a variety of DNA quantities, charges, and internal pore volumes. These parameters were used to optimize the DNA sensors based on these coatings. Thus, doxorubicin was determined to have limits of detection of 0.01 nM (cone configuration), 0.05 nM (partial cone configuration), and 0.10 nM (1,3-alternate configuration of the macrocycle core). Substitution of native DNA with aptamer specific to aflatoxin M1 resulted in the detection of the toxin in the range of 20 to 200 ng/L (limit of detection 5 ng/L). The aptasensor was tested in spiked milk samples and showed a recovery of 80 and 85% for 20 and 50 ng/L of the aflatoxin M1, respectively.

Phenothiazine oligomers were synthesized by oxidative oligomerization. Optimal reaction conditions were found: phenothiazine reacts with ammonium persulfate and silver (I), nickel (II), copper (II), and iron (III) nitrates in mechanochemical conditions in a mixture with p-toluenesulfonic acid. Effect of oxidants on the structure and morphology of oligomers was demonstrated by complex of physical methods, most prominent structural difference is demonstrated by MALDI mass-spectrometry and method of scanning electron microscopy. The use of metal nitrates leads to formation of oxidized oligophenothiazines (mass peaks correspond to side reactions leading to hydroxyl groups) which form bulk, granular material, the use of ammonium persulfate leads to formation of mesoporous material. Dielectric permittivity of oxidized oligomers is 2.9 - 10.2 in the case of metal nitrates while the maximum of permittivity was obtained for nanostructured oligophenothiazine - 4027.3 which was synthesized with ammonium persulfate as an oxidizing agent. We conclude that side reactions affect the morphology and dielectric permittivity - i.e. hydroxyl, quinone groups participate in forming intermolecular hydrogen bonds while in oligophenothiazine these interactions are less significant, which leads to mesoporous structure.

The interaction of (L)-lactic acid with p-tert-butylthiacalix[4]arene containing ethoxycarbonyl fragments in the 1,3-alternate conformation was studied in tetraglyme. For the first time, the lactic acid oligomer was obtained by polycondensation with the macrocycle and characterized by H-1, C-13 NMR, IR spectroscopy, MALDI mass spectrometry and gel permeation chromatography. Thermal stability of the obtained copolyester of lactic acid and thiacalix[4]arene was studied by TG/DSC analysis and the effect of the macrocydic platform on its thermal properties was shown. Copolyester obtained was thermally more stable than oligolactic acid. Self-assembly of synthesized oligomer was studied by dynamic light scattering method. It was shown that monodisperse particles (PDI = 0.13) with the size of 208 +/- 4 nm are formed in CH3CN solution at 2.5 x 10(-5) M concentration. (C) 2019 Elsevier B.V. All rights reserved.