Polymeric materials as biomaterials under particular consideration of biodegradable polymers

Biomaterials may be defined as artificial materials which fulfill the mechanical requirements and interact with the biosystem they are in contact with in same way as a natural material would react in the same place. While the requirements of mechanical properties can be reached by suitable organo-polymeric and inorganic materials the interfacial biocompatiblity is neither understood in all its complexity nor can be fulfilled by any of the applied materials. Surface modification and characterization with greatest scrutiny and the observation of the answer of selected parameters of the biosystem are a subject of utmost interest. A few examples will be presented. In the long range, however, it has to be considered that any material is degraded and hence should present continuously a renewable biocompatible surface. On the other hand, materials are desired which deliberately are biodegradable. Presently available materials are polylactides and copolymers. An alternative could be presented by polydepsipeptides because of two reasons, (i) the local concentration of acid formed upon degradation would be reduced as compared to polylactides which in certain cases might be advantageous and (ii) the aminoacid units could carry side groups with bioactive molecules attached. Therefore, a new method of acylation of an aminoacid with a hydroxyacid is presented as well as the cyclisation to result in the cyclic depsipeptide and the polymerisation to yield the polydepsipeptide. The microstructure of the polymers, the thermal properties and the degradation behaviour is presented.     

Model analysis of zeolite-like phosphates and their adsorption complexes with water molecules

Molecular models of borophosphates, aluminophosphates, and silicon-containing derivatives of these phosphates have been subjected to quantum-chemical analysis in the MNDO approximation. Bonding energies of these compounds with water molecules have been calculated. Incorporation of silicon atoms into the phosphate matrix increases its hydrophilicity and acidity.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 30, No. 4, pp. 223–226, July–August, 1994.     

Gas phase reactions of trimethyl borate with phosphates and their non-covalent complexes

Using a quadrupole ion trap mass spectrometer, trimethyl borate was allowed to react with dihydrogen phosphate, deprotonated O-phosphoserine, and a set of hydrogen bonded complexes involving dihydrogen phosphate and neutral acids (phosphoric acid, acetic acid, serine, and O-phosphoserine). The reactions show a consistent pattern in which the initial attack leads to addition with the loss of one or two CH3OH molecules. Collision-activated dissociation (CAD) experiments on the reaction products generally lead to the loss of an additional CH3OH molecule. In no case is a partner from the original hydrogen-bonded complex lost. The results indicate that the reactions lead to structures where the phosphate and its complex partner are covalently bound to the boron. For each of the reactions, rate constants were determined. In the course of CAD experiments (up to MS5), several novel borophosphate structures were identified. The work is supported by ab initio calculations on selected species.     

New metal compounds and their reactivity towards bovine milk casein

The l,2-bis(sulphapyridyl)oxamide ligand [L] and its complexes with Fe^III, Co^II, Cu^II and Zn^II chloride were synthesized and characterized by elemental analyses, i.r., n.m.r., e.p.r. and u.v.–vis. spectroscopy and molar conductance measurements. Spectroscopic studies show that all the complexes are octahedral and covalent. The electrochemical behaviour of the Co^II complex was monitored by cyclic voltammetry in a buffer/DMF solution (95:5). The E ⁰ values –0.622 and –0.502 V reveal a reversible one electron redox wave attributed to a Co^II/Co^I redox couple at a scan rate of 0.1 V s^–1. The interaction of the Co^II complex with bovine milk casein (BMC) was studied at the same scan rate, which reveals a strong binding as the E ⁰ values shift to more negative potential (E ⁰ = –0.908 and –0.703 V). The cyclic voltammograms of the Co^II complex bound by BMC were recorded at different pH's. The plot of E ⁰ versus pH showed that E ⁰ values are maximal at pH 7.4 indicating good interaction between the BMC and the Co^II complex which is further confirmed by kinetic data. The kinetic studies of the Co^II complex bound to BMC was monitored in phosphate buffer solution at different pH's by spectrophotometry. The absorbance changes were monitored at 278 nm ( _max for BMC) with respect to time and pseudo-first-order rate constants, K _obs, were obtained from the slope and intercept of the straight line using the least squares regression method. The plot of absorbance versus time at different pH's was linear up to 80% completion of the reaction. The pH-rate profile data reveals that the reactions are pH dependent.     

Polymeric nitrile–palladium chloride complexes and their reaction with olefins

Polymers containing cyano groups connected to the polymeric chain by means of at least one methylene group adsorb palladium dichloride reversibly from its slightly acidic solutions and form surface complexes of the probable structure (? CH₂CN)₂? PdCl₂. These complexes can adsorb gaseous olefins; ethylene is consumed continuously, but adsorption of propylene and 1-butene reaches saturation. Additional ethylene can be added to the propylene or 1-butene adsorbate. Hydrolysis of the surface olefinic complexes yields aldehydes, the ethylene complex giving acetaldehyde and butanal, the mixed ethylene–1-butene complex giving acetaldehyde, butanal and hexanal.     

Production of activated carbons from biodegradable waste materials as an alternative way of their utilisation

New carbonaceous adsorbents were prepared by means of direct, physical and chemical activation of corn cobs and cherry stones as well as coffee and tobacco industry waste materials. The effect of activation method on the textural parameters, acid-base character of the surface and sorption properties toward toxic gases of the materials obtained was tested. Depending on the precursor as well as method of preparation, the final products were micro/mesoporous activated carbons of surface area reaching to 1426 m²/g, showing largely different acid-base properties of the surface. The results obtained in our study have proved that a suitable choice of the activation procedure for industrial and agricultural biodegradable waste materials permits production of cheap carbonaceous adsorbents with very high sorption capacity towards nitrogen dioxide and hydrogen sulphide reaching to 83 mg NO₂/g_ads and 215 mg H₂S/g_ads, respectively.     

Polymeric cobalt-schiff-base and -porphyrin complexes as a dioxygen device

New functions of polymeric cobalt complexes were examined using their oxygen-binding reactions in the solid state. An oxygen-releasing device was prepared by compositing the oxygen-binding but electrically insulating cobalt-Schiff-base or -porphyrin complex with a conductive carbon powder. The device quickly released the absorbed oxygen in response to an applied voltage. A polymer film containing the cobalt-Schiff-base complex reversibly stretched in response to the atmospheric oxygen concentration. The driving force of the stretching of the film was attributed to the crystal structure change of the complex before and after the oxygen-binding.     

Estimation of substituted phosphates such as dibutyl and monobutyl phosphates, based on their reaction with lanthanum-Xylenol Orange complex

Development of a new method for the estimation of substituted phosphates such as dibutyl phosphate (DBP) and monobutyl phosphate (MBP) is described in this paper. The method is based on the decolouration of lanthanum-Xylenol Orange complex by DBP and MBP at pH 5.     

Microwave-assisted synthesis of tin sulfide nanoflakes and their electrochemical performance as Li-inserting materials

A novel and quick method has been developed for the preparation of tin sulfide (SnS and SnS₂) nanoflakes in high yield (≈93%) by a microwave irradiation technique for 10–40 min. The sulfides were synthesized in a simple domestic microwave oven (DMO) using stannic chloride and stanous chloride as the precursors of tin and thiourea as the precursor of sulfur in ethylene glycol under argon atmosphere. Elemental sulfur and sodium thiosulfate were also tried as precursors of sulfur. The structures, morphologies, compositions, and physical properties of the products were characterized by powder X-ray diffraction (XRD), differential scanning calorimetry, energy dispersive X-ray analysis, transmission electron microscopy, selected area electron diffraction, Raman spectroscopy, and standard electrochemical techniques. The XRD patterns indicate that the as-synthesized product, obtained after microwave irradiation, is crystalline orthorhombic in the case of the SnS phase and amorphous in the case of SnS₂. Heat treatment of this SnS₂ produced a crystalline hexagonal phase. A possible mechanism for the formation of the tin sulfide nanoflakes is proposed herein. The electrochemical performance of these materials as Li-insertion materials was investigated in a number of electrolyte solutions and was found to be highly sensitive to the solution composition. A stable reversible capacity higher than 600 mAh/g could be obtained with SnS electrodes.     

Polymeric complexes of chitosan with proteins and hydroxyl-containing polymers

The structures of polymeric complexes of chitosan with methyl cellulose, lactoserum protein, gelatin, and polyvinyl alcohol were simulated on a computer. The mechanism of metal captures in cavities of these complexes was analyzed. The conformational and geometric characteristics of polymeric complexes of chitosan were obtained. The properties and structure of complexes in solutions and in the bulk were examined.     

FTIR features of lithium-iron phosphates as electrode materials for rechargeable lithium batteries

The essential structural features of lithium-metal phosphates (LMP) have been studied using FTIR spectroscopy which is a sensitive tool to probe the local environment in the solid materials. Various LMP materials where M is iron have been investigated including phospho-olivine LiFePO(4), diphosphate LiFeP(2)O(7), Nasicon-type phosphate Li(3)Fe(2)(PO(4))(3) and dihydrate FePO(4).2H(2)O. Vitreous and amorphous materials are also considered. Analysis of internal and external modes of vibration allows to distinguish between the different phases and the type of cationic environment in the framework. Results corroborate the contribution of the main factors which are responsible for the complexity of the spectra, i.e. departure from ideal symmetry, interactions between polyhedra, bridging atoms and lattice distortion.     

硫脲壳聚糖-银配合物的制备及其结构和抑菌性能

合成了一系列不同银含量的硫脲壳聚糖-银配合物;利用傅立叶变换红外光谱分析了合成产物的结构,并测定了壳聚糖、硫脲壳聚糖及4种硫脲壳聚糖-Ag配合物对细菌和植物病原菌的抑菌性能.结果表明:硫脲壳聚糖-Ag配合物的抑菌性能优于单一的壳聚糖和硫脲壳聚糖;随着硫脲壳聚糖-Ag配合物中银含量的增大,抑菌效果明显增强.     

Polymeric heterometallic CuII dimethylmalonate complexes with potassium and cadmium ions

A reaction of (HPiv)₂Cu₂(Piv)₄ with dimethylmalonic acid dipotassium salt (K₂Me₂mal) leads to the formation of a cage coordination polymer {(μ-H₂O)₆K₈[(μ-H₂O)Cu-(μ₃,κ²-Me₂mal)(μ₆,κ²-Me₂mal)]₂[Cu₂(μ₅,κ²-Me₂mal)₂(μ₅,κ²-Me₂mal)₂]}n (1). It was found that when 1 reacted with CdSO₄·8H₂O in a mixture of EtOH-H₂O (3: 1), the potassium ions in 1 were displaced with cadmium(ii) ions with the formation of a heterometallic 1D-polymer [(κ¹-H₂O)₄CdCu(μ,κ²-Me₂mal)₂] _n (2). Compounds 1 and 2 were characterized by X-ray crystallography and ESR spectroscopy.     

Chemistry of glycosyl phosphates and their derivatives

Conclusions 4,6-Dtdesoxy-- and-L-lyxohexopyranosyl phosphates were synthesized.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 887–891, April, 1976.The authors are deeply indebted to K. S. Adamyanets for submitting samples of the initial monosaccharides.See [1] for preceding communication.     

Chemistry of glycosyl phosphates and their derivatives

Conclusions We were the first to synthesize 4-thio-ga-D-glucopyranosyl phosphate.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 425–430, February, 1973.     

Polymeric cryogels as a new family of macroporous and supermacroporous materials for biotechnological purposes

The review is devoted to a specific kind of polymeric gels formed as a result of non-deep freezing of solutions or colloidal sols of the corresponding precursors. These materials are termed as cryogels. They possess a series of unique properties, first of all, the specific character of porosity (macroporous cryogels with the pore cross-section from tenth fractions of μm to ∼10 μm and supermacroporous (gigaporous) cryogels with pores of tens and hundreds of μm) and are attractive from the viewpoint of biotechnological implementation. Approaches to the preparation of the so-called “smart” composites based on the cryogels are considered. The use of various cryogels as carriers of immobilized biocatalysts (enzymes, cells), matrices for wide-porous affinity sorbents and immunosorbents, and spongy scaffolds for 3D culturing of animal cells is discussed. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 996–1013, May, 2008.