Enzymatic Decomposition of Chitosan-Based Film Materials Modified by Antibiotics of the Cephalosporin Series

The enzymatic decomposition of film materials based on chitosan with inclusions of cephalosporin antibiotics on a substrate impregnated with Ringer–Locke’s solution was studied. The introduction of antibiotics led to a decrease in the rate of the enzymatic decomposition of chitosan, as in the case of chitosan lysis in the presence of aminoglycoside antibiotics. A possible reason for the decrease in the rate of the enzymatic decomposition of chitosan is suppression of polyelectrolyte swelling in the presence of low-molecular electrolytes including medicinal agents. The introduction of drugs in the chitosan-based film is a potential method for selectively decreasing the rate of enzymatic hydrolysis of chitosan for increasing the service life of the film material on a wound surface.     

Bio-inspired network optimization in soft materials — Insights from the plant cell wall

The dynamic-mechanical responses of ionotropic gels made from the biopolymer pectin have recently been investigated by microrheological experiments and found to exhibit behaviour indicative of semi-flexible polymer networks. In this work we investigate the gelling behaviour of pectin systems in which an enzyme (pectinmethylesterase, PME) is used to liberate ion-binding sites on initially inert polymers, while in the presence of ions. This is in contrast to the previous work, where it was the release of ions (rather than ion-binding groups) that was controlled and the polymers had pre-existing cross-linkable moieties. In stark contrast to the semi-flexible network paradigm of biological gels and the previous work on pectin, the gels studied herein exhibit the properties of chemically cross-linked networks of flexible polymers.     

Application of EPR spectroscopy to examination of gentamicin and kanamycin binding to DOPA-melanin

Electron paramagnetic resonance (EPR) spectroscopy was applied to measure the influence of two aminoglycoside antibiotics: gentamicin and kanamycin on free radical propertis of DOPA-melanin. DOPA-melanin was formed by oxidative polymerization of 3,4-dihydroxyphenylalanine. Different concentrations of gentamicin and kanamycin (from 1·10⁻⁴ to 1·10⁻² M) were used. o-Semiquinone free radicals with ag factor of 2.0043 were found in all studied melanin samples. Their concentrations in the DOPA-melanin-drug complexes were higher than in DOPA-melanin, and increased with the increase of gentamicin and kanamycin concentration. A single EPR line of the analyzed samples (ΔB _pp, 0.48-0.52 mT) indicates that aminoglycoside antibiotics do not create a new type of free radicals in DOPA-melanin. Microwave saturation behavior of the experimental lines indicates the homogeneous broadening of resonance absorption curves for DOPA-melanin and its complexes with aminoglycosides. The EPR lines saturate at low microwave powers. Slow spin-lattice relaxation processes were characteristic for all studied melanin samples.     

Preparation and properties of kenaf dust-filled chitosan biocomposites

Kenaf dust filled chitosan biocomposites have been prepared using a solution blending method. Diluted acetic acid was used as medium to dissolve the chitosan powder. Kenaf dust particles were dispersed in the chitosan solution using a high speed homogenizer. Chitosan biocomposites with five different compositions of kenaf loading (w/w) were prepared. The biocomposites were evaluated in terms of mechanical, chemical and micro-structural properties. The maximum tensile strength, tensile strain and toughness values were obtained from biocomposites containing 28% of kenaf dust, while pure chitosan film exhibit the lowest value as expected. Morphological study on the tensile fracture surface of the biocomposites under FESEM showed the interconnected structure of chitosan matrix with fine distribution of kenaf dust. From the FT-IR spectrum, the finger print peak of chitosan was detected (3233 cm^?1) as well as the increasing in intensity of typical functional groups (aldehyde, primary amine and ammonium ions), indicating a strong interaction between kenaf dust and chitosan matrix.     

Chitosan magnetic microspheres for technological applications: Preparation and characterization

One of the major applications of chitosan and its many derivatives are based on its ability to bind strongly heavy and toxic metal ions. In this study chitosan magnetic microspheres have been synthesized. Acetic acid (1%w/v) solution was used as solvent for the chitosan polymer solution (2%w/v) where magnetite nanoparticles were suspended in order to obtain a stable ferrofluid. Glutaraldehyde was used as cross-linker. The magnetic characteristic of these materials allows an easy removal after use if is necessary. The morphological characterization of the microspheres shows that they can be produced in the size range 800–1100 μm.The adsorption of Cu(II) onto chitosan–magnetite nanoparticles was studied in batch system. A second-order kinetic model was used to fit the kinetic data, leading to an equilibrium adsorption capacity of 19 mg Cu/g chitosan.     

Probabilistic model for fluences and peak fluxes of solar energetic particles.

The model is intended for calculating the probability for solar energetic particles (SEP), i.e., protons and Z=2-28 ions, to have an effect on hardware and on biological and other objects in the space. The model describes the probability for the > or = 10 MeV/nucleon SEP fluences and peak fluxes to occur in the near-Earth space beyond the Earth magnetosphere under varying solar activity. The physical prerequisites of the model are as follows. 1. The occurrence of SEP is a probabilistic process. 2. The mean SEP occurrence frequency is a power-law function of solar activity (sunspot number). 3. The SEP size (taken to be the > or = 30 MeV proton fluence size) distribution is a power-law function within a 10(5)-10(11) proton/cm2 range. 4. The SEP event particle energy spectra are described by a common function whose parameters are distributed log-normally. 5. The SEP mean composition is energy-dependent and suffers fluctuations described by log-normal functions in separate events.     

Study on factors governing the conductivity performance of acylated chitosan-NaI electrolyte system

Hexanoyl chitosan and lauroyl chitosan were prepared by acyl modification of chitosan. Films of hexanoyl chitosan- and lauroyl chitosan-based polymer electrolytes incorporated with different weight concentrations of sodium iodide (NaI) were prepared using the solution casting technique. FTIR and differential scanning calorimetry (DSC) results suggested that NaI interacted with both hexanoyl chitosan and lauroyl chitosan. Maximum conductivities of 1.3 × 10^?6 and 1.1 × 10^?8 S cm^?1 are achieved for hexanoyl chitosan and lauroyl chitosan, respectively. Higher conductivity in hexanoyl chitosan is attributed to higher ion mobility as supported by DSC results. The dielectric constants of neat hexanoyl chitosan and lauroyl chitosan are 2.7 and 1.9, respectively, estimated from impedance spectroscopy. Higher dielectric constant of hexanoyl chitosan resulted in greater NaI dissociation and hence higher conductivity. Deconvolution of O═C-NHR and OCOR bands of polymer has been carried out to estimate the amount of dissociated Na⁺ ions from NaI. The findings were in good agreement with conductivity results. In order to assess quantitatively, the conductivity, parameter number, n, and mobility, μ, of ions were calculated using impedance spectroscopy. XRD results showed the influence of NaI on the crystalline content of the electrolyte system. Sample with lower crystalline content exhibited higher conductivity.     

Geometrical model approximation for ionization cross sections of atoms and ions in ion-atom collisions

The applicability of the geometrical model (GM) proposed in [14, 15] to calculate the ionization probability and cross section of atoms and ions during collisions with ions, including structural ions, was studied at high velocities of partners. The GM represents a version of the classical impulse approximation. It was shown that the GM in all cases under consideration allows estimation of the ionization probability and total corss section of an atom or an ion during collisions with ions with deviations of no more than 50% from the results of the classical Monte Carlo method. GM calculations are rather simple in computation respect and limit the ionization probability by unity at arbitrary impact parameters.     

Proton-conducting biopolymer electrolytes based on pectin doped with NH4X (X=Cl,Br)

Research has been undertaken to develop polymer electrolytes based on biodegradable natural polymers such as cellulose acetate, starch, gelatin, and chitosan, which are being used as polymer hosts for obtaining new polymer electrolytes for their applications in various electrochemical devices such as batteries, sensors, and electrochromic windows. Pectin is a naturally available material which is extracted from the skin of citrus fruits. Pectins, also known as pectic polysaccharides, are rich in galacturonic acid. The present study focuses on the proton-conducting polymer electrolytes based on the biopolymer pectin doped with ammonium chloride (NH₄Cl) and ammonium bromide (NH₄Br) prepared by solution casting technique. The prepared membranes are characterized using XRD, FTIR, and AC impedance techniques to study their complexation behavior, amorphous nature, and electrical properties. The conductivity of pure pectin membrane has been found to be 9.41 × 10⁻⁷ S cm⁻¹. The polymer systems with 30 mol% NH₄Cl-doped pectin and 40 mol% NH₄Br-doped pectin have been found to have maximum ionic conductivity of 4.52 × 10⁻⁴ and 1.07 × 10⁻³ S cm⁻¹, respectively. The conductivity value has increased by three orders of magnitude compared to pure pectin membrane. The dielectric behavior of both the systems has been explained using dielectric permittivity and electric modulus spectra.

     

重离子核反应对单粒子翻转的影响（英文）

LET作为一个传统的工程参量,并不能完全满足单粒子翻转数据表征的需要,而且也不能直接地反映核反应的一些特性(包括核反应概率与次级粒子),因此研究了重离子与器件作用过程中核反应对单粒子翻转的影响。基于蒙特卡罗模拟与深入的分析,本研究对比了在直接电离与考虑核反应两种模式下的模拟结果。在模拟中,利用不同的重离子表征了核反应在单粒子翻转发生中所起的作用。结果显示,核反应对单粒子翻转截面的贡献依赖于离子的能量,并呈现非单调的变化关系。基于模拟的结果,建议用重离子核反应引起单粒子翻转的最恶劣情况来预估空间单粒子翻转率。     

Effect of chitosan and thiolated chitosan coating on the inhibition behaviour of PIBCA nanoparticles against intestinal metallopeptidases

Surface modified nanoparticles composed of poly(isobutylcyanoacrylate) (PIBCA) cores surrounded by a chitosan and thiolated chitosan gel layer were prepared and characterized in previous works. The presence of such biopolymers on the nanoparticle surface conferred those nanosystems interesting characteristics that might partially overcome the gastrointestinal enzymatic barrier, improving the oral administration of pharmacologically active peptides. In the present work, the antiprotease behaviour of this family of core–shell nanoparticles was in vitro tested against two model metallopeptidases present in the gastrointestinal tract (GIT): Carboxypeptidase A -CP A- (luminal protease) and Leucine Aminopeptidase M -LAP M- (membrane protease). As previous step, the zinc-binding capacity of these nanoparticles was evaluated. Interestingly, an improvement of both the zinc-binding capacity and the antiprotease effect of chitosan was observed when the biopolymers (chitosan and thiolated chitosan) were used as coating component of the core–shell nanoparticles, in comparison with their behaviour in solution, thanks to the different biopolymer chains rearrangement. The presence of amino, hydroxyl and thiol groups on the nanoparticle surface promoted zinc binding and hence the inhibition of the metallopeptidases analysed. On the contrary, the occurrence of a cross-linked structure in the gel layer surrounding the PIBCA cores of thiolated formulations, due to the formation of interchain and intrachain disulphide bonds, partially limited the inhibition of the proteases. The low accessibility of cations to the active groups of the cross-linked polymeric shell was postulated as a possible explanation of this behaviour. Results obtained in this work make this family of surface-modified nanocarriers promising candidates for the successfull administration of pharmacologically active peptides and proteins by the oral route.     

Determination of the concentration of cephalosporin antibiotics in blood by infrared spectroscopy

We studied IR spectra of blood and cephalosporin antibiotics that are widely used in medical practice. We established the spectral regions that are suitable for determining their concentration in blood. It is shown using the antibiotic cephtriacson as an example that the IR spectroscopy method allows one to determine the concentrations of antibiotics in blood in the range of practical medical interest. We examined the possible transfer of antibiotics by blood erythrocytes. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 4, pp. 512–515, July–August, 2007.     

多壁碳纳米管/铋膜修饰电极示差脉冲溶出伏安法测定水中镉和铅

制备多壁碳纳米管/壳聚糖纳米复合物修饰玻碳电极,用于同位镀铋膜法连续测定水中镉和铅离子的含量.将多壁碳纳米管分散在壳聚糖溶液中,滴涂在玻碳电极表面制得修饰电极;在含铋的溶液中,采用示差脉冲溶出伏安法测定了镉、铅离子的浓度;考察了沉积电位、富集时间对溶出电流的影响.在优化的实验条件下,对浓度在0-0.2μmol/L范围内...     

萘酰亚胺接枝壳聚糖Al3+荧光探针的合成及光谱性能研究

以1,8-萘酰亚胺、壳聚糖、盐酸吗啉胍为原料,通过酰亚胺化、席夫碱等反应,设计合成了一种萘酰亚胺接枝壳聚糖类增强型荧光探针（NCFP）。采用红外、核磁共振等技术对其结构进行表征,利用荧光光谱研究了其光谱性能及对金属离子的识别作用。研究结果表明,合成的荧光探针对Al³⁺具有较高的选择识别性能,且受常见离子的干扰较小。探针的荧光强度与Al³⁺浓度（29.90~253.41 μmol/L）有良好的线性关系,线性相关系数R²=0.997 9,Al³⁺的最低检出限达4.279 μmol/L,Job's曲线表明,荧光探针与Al³⁺的络合比为1：1。     

Solid-state structure of copper complexes of <Emphasis Type="Italic">N</Emphasis>-(2-carboxyethyl)chitosan

The sorptivity for ions of the Irving-Williams series (Zn²⁺, Cu²⁺, Co²⁺, Ni²⁺) was estimated for the chelate sorbent N-(2-carboxyethyl)chitosan cross-linked by nanosecond electron-beam irradiation. The maximum capacity reaches 3.7 mmol/g using a mixture of the appropriate sulfates at pH 4.5. The selectivity of copper sorption is 80%. The structure of the coordination sphere of the copper complexes with N-(2-carboxyethyl)chitosan was investigated by ESR spectroscopy. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 5, pp. 635–639, September–October, 2008.     

Novel pH-Sensitive Lactic Acid Oligomer Grafted Chitosan Hydrogel for Controlled Drug Release

A pH-sensitive hydrogel, using chitosan as hydrophilic segment and lactic acid oligomer (LAO) as hydrophobic segment, was successfully synthesized through a dehydration reaction between amino and carboxyl groups. Scanning electron microscope (SEM) images revealed that the channel-like network structure of the as-prepared hydrogels, which plays an important role in controllable drug release behavior, was gradually collapsed with increasing content of lactic acid. Fourier-transform infrared (FTIR) spectra were obtained to demonstrate the occurrence of the dehydration reaction. Furthermore, the swelling ratio measurement and release study were performed, and the results showed that the chitosan/LAO hydrogel had an outstanding pH-sensitive property, and thus has high potential for usage in controlled-drug release.     

Citrus pectin modified by microfluidization and ultrasonication: Improved emulsifying and encapsulation properties

In this study, modified citrus pectin treated with a combination of microfluidization and ultrasonication was compared to the original and ultrasonication treated pectin on hydrodynamic diameter, molecular weight, polydispersity, zeta potential, apparent viscosity, Fourier-transform infrared spectroscopy (FTIR), 2,2-diphenyl-1-picryl hydrazyl (DPPH) radical scavenging capacity, scanning electron microscope (SEM), atomic force microscopy (AFM), their emulsifying properties and encapsulation properties. Modified pectin treated with a combination of microfluidization and moderate ultrasonication (MUB) was found to have lowest hydrodynamic diameter (418 nm), molecular weight (237.69 kDa) and polydispersity (0.12), and relatively low apparent viscosity among all pectin samples. Furthermore, it showed significantly higher DPPH radical scavenging capacity than the original pectin although only slightly higher than that of ultrasonication treated one (UB). MUB showed a thin fibrous morphology and decreased degree of branching from SEM and AFM. Emulsion stabilized by MUB had highest centrifugal and thermal stability compared to emulsions stabilized by UB and the original pectin. This could be attributed to higher interfacial loading of MUB (17.90 mg/m²) forming more compact interfacial layer observed by confocal laser scanning microscopy (CLSM). Moreover, both MUB and UB exhibited improved encapsulation functionality to protect cholecalciferol (vitamin D₃) from UV degradation compared to the original pectin.     

Influence of surface morphology of cpTi on the adsorption and attachment of collagen/chitosan

The surface microtopography of implant influences distinctly the rate of bone-formation and the ratio of bone-implant contact. However, it is indicated that the surface of titanium implant existed contamination after different surface treatments. Chitosan is one of the most abundant natural polymers for its adsorption property for metal ions. In this study, we report on the pretreatment of the metal surface and aim to compare the efficacy of three treatments for the binding ability of collagen/chitosan (CL/CS). The compound of collagen and chitosan was immobilized on the titanium oxide and the morphology and chemical composition were used to characterize the titanium surfaces by scanning electron microscope (SEM), X-ray photoelectron spectrometry (XPS). The result showed that the surface displayed irregularities after roughness treatments and the rough surface was beneficial to the adsorption and attachment of CL/CS. The combination of CL/CS was related with the titanium surface character.     

New luminophor-activators based on (fluoro)quinolone antibacterials

It was shown that (fluoro)quinolone antibiotics form strongly fluorescent solid-state complexes with Eu(III) and Tb(III) lanthanide ions, with a wavelength red-shift beneficial for applications to greenhouse-cover polymers. Complexes with optimal properties were prepared by the mechanical activation of fine-dispersed composite mixtures with the lanthanide salts. The spectral properties, photo-stability to UV-light, and compatibility with the polyethylene matrix were investigated. The formulation additives of the tablet forms of the antibiotic medicines did not quench the fluorescence from the lanthanide ions. Therefore, the outdated drug forms of the antibiotics can serve as cheap recyclable sources for the covering material of greenhouses. In addition, diphenylguanidine (DPG) was investigated as a coligand. DPG enhanced fluorescence of the fluoroquinolone complexes by decreasing the non-radiative energy loss through O-H vibration of H₂O.