Preparation and nitromethane sensing properties of chitosan thin films containing pyrene and β-cyclodextrin units

Chitosan thin films, coated on a quartz plate surface, containing pyrene (Py) and β-cyclodextrin (β-CD) units on their surfaces have been designed and prepared as novel sensing materials for nitromethane. Fluorescence studies revealed that the immobilized Py was included in the cavity of its neighbor β-CD. This structure makes the fluorescence emission of the films could not be quenched by commonly used quenchers, including copper, cobalt and some other transition metal salts, KI and acrylamide. However, addition of nitromethane quenched the emission dramatically. Considering the high selectivity and sensitivity, great reversibility and stability, wide dynamic range and long storage time, it is proposed that these novel films could be applicable to the sensing of nitromethane in some energetic fuels.     

Interactions between preservatives and 2-hydroxypropyl-β-cyclodextrin

The interactions between several commonly used preservatives, i.e. benzalkonium chloride, chlorhexidine gluconate, chlorobutanol, methylparaben and propylparaben, and 2-hydroxypropyl-β-cyclodextrin were investigated. The interactions were shown to be twofold. Firstly, the preservative molecules can displace the drug molecules from the cyclodextrin cavity, thus, reducing the solubilizing effects of the cyclodextrin. Secondly, the antimicrobial activity of the preservatives were reduced by formation of preservative-cyclodextrin inclusion complexes. The magnitude of the interactions were dependent on the degree of complexation.     

Cyclodextrin nanosponges to enhance the dissolution profile of quercetin by inclusion complex formation

ABSTRACT

The therapeutic potential of quercetin is mostly hampered by its low water solubility and poor absorption. The aim of this study was to enhance the dissolution rate of quercetin by molecular encapsulation with cyclodextrin nanosponges. The inclusion complexes were obtained by freeze-drying method. Inclusion complexes were characterized by Fourier Transformed Infrared Spectroscopy (FTIR), x-ray diffraction (XRD), Differential Scanning Calorimetry (DSC), transmission electron microscopy (TEM), and dissolution testing. FTIR, XRD, and DSC studies confirmed the interactions of quercetin with nanosponges. TEM images revealed the spherical morphology of complexes. The dissolution of the drug nanosponge complex was significantly higher compared with the pure drug in simulated intestinal fluid (SIF; pH 6.8). The results indicated that the degree of cross-linking has the significant influence on dissolution. Nanosponges with lower degree of cross-linking released 91% of the drug within 45 min, whereas nanosponges with higher degree of cross-linking resulted in sustained release up to 24 h.     

Inclusion complexation of vitamin a palmitate with β-cyclodextrin in aqueous solution

Study of the inclusion complex between vitamin A palmitate and β-cyclodextrin in aqueous solution was performed to determine the stoichiometry and the association constant of the complex by the phase solubility diagram and fluorescence intensity measurements.     

Photophysical properties of β-alkylated quater-, octa-, dodeca- and hexadecatiophenes

The order and deactivation of excited electronic states of β-alkylated oligothiophenes consisting of n = 4, 8, 12 and 16 thiophene rings are investigated by absorption spectroscopy as well as by steady state and time resolved fluorescence spectroscopy. Transition energies in oligothiophenes are linearly dependent on reciprocal chain-length only for n <- 8. For n > 8, chain-length dependence is correctly described by calculations which take alternating bond-lengths into account. β-Alkylation leads to enhanced nonplanarity in the ground state and thus to blue-shifted absorption maxima. Due to the quinoid structure of the excited state, which leads to planarization, fluorescence maxima are not blue-shifted versus unsubstituted oligothiophenes. In solution, up to the longest chain under investigation, N = 16, the 1B_u state is energetically below the 2A_g state, as inferred from comparison of radiative rate constants of fluorescence and absorption according to the Strickler-Berg relationship. 113, is also below 2A_g in the solid state, as concluded from the coincidence of the 0-0-transitions of absorption and fluorescence.     

Study of inclusion complex formation between chlorpromazine hydrochloride,as an antiemetic drug,and β-cyclodextrin,using conductometric technique

The behavior of micellization of chlorpromazine hydrochloride (CPH) as an antiemetic drug and its inclusion complex formation with β-cyclodextrin (β-CD) was studied using conductometric technique. The binding or association constant of the complexation equilibrium is evaluated from conductometric measurements by using a nonlinear regression method. The resulting K values for micellization as well as complexation are analyzed. The experiments were carried out at different temperatures. It has been found that CPH form only the 1:1 complex. The association constant values are used for evaluation of thermodynamic parameters of complexation, such as ΔG_complex°, ΔH_complex° and ΔS_complex°.     

Comparative study on Inclusion compounds of 4-Biphenylacetic acid with β-Cyclodextrin, Hydroxypropylated-β-Cyclodextrins, and methylated-β-Cyclodextrins

The inclusion behavior of Hydroxypropyl-β-Cyclodextrin (HP-β-Cyd) and of methylated-β-Cyclodextrins, heptakis-(2,6-di-O-methyl)-β-Cyclodextrin (DM-β-Cyd) and heptakis-(2,3,6-tri-O-methyl)-β-Cyclodextrin (TM-β-Cyd), in solution and solid state was compared with that of natural β-Cyclodextrin (β-Cyd) using an anti-inflammatory drug, 4-biphenylacetic acid (BPAA), as a guest molecule. The solubility of BPAA with β-Cyd and β-Cyd derivatives in aqueous solution were determined. Stability constants were calculated by phase solubility method at various pH values and temperatures. The formation of inclusion complexes with β-Cyd and β-Cyd derivatives in the solid slate were confirmed by infrared spectroscopy, differential scanning calorimetry and X-Ray diffractometry, and in the liquid phase by ultraviolet spectroscopy, circular dichroism and NMR studies. Dissolution rate and “in vitro” release of BPAA from complexes were examined. The results obtained suggest that DM-β-Cyd is more effective than other β-Cyclodextrins in improving the pharmaceutical properties of BPAA.     

Synthesis and Characterization of Thrombin Conjugated γ‐Fe2O3 Magnetic Nanoparticles for Hemostasis

Thrombin is the final protease produced in the clotting pathways. Thrombin has been used in the clinic more than six decades for topical hemostasis and wound management. In human plasma the half‐life of thrombin is shorter than 15 seconds due to close control by inhibitors. In order to stabilize thrombin, this enzyme was conjugated covalently and physically to γ‐Fe₂O₃ magnetic nanoparticles. The physical conjugation was accomplished through adsorption of thrombin to BSA coating on the nanoparticles. The coagulant activity of the covalently bound thrombin was significantly lower than that of the physically adsorbed thrombin. Leakage of the physically bound thrombin into PBS containing 4% HSA was negligible. The physical conjugation of thrombin onto the nanoparticles stabilized the thrombin against its major inhibitor antithrombin III and improved its storage stability. At optimal CaCl₂ concentration, the clotting time by the bound thrombin is shorter than that of the free enzyme. This novel conjugated thrombin may be an efficient candidate for topical hemostasis and wound healing.     

Inclusion Complexes of Tolnaftate with β-Cyclodextrin and Hydroxypropyl β-Cyclodextrin

Tolnaftate, an antifungal agent, was found to form inclusion complexes with both β-cyclodextrin (β-CD) and hydroxypropyl β-cyclodextrins (HPBCDs) with two different degrees of substitution [HPBCD(A)-8% and HPBCD(B)-3%]. Complex formation in the solution state was studied using phase solubility and spectral shift methods. Solid complexes were prepared by the coprecipitation method. Solubilities and dissolution rates were determined for each solid complex, its corresponding physical mixture, and free drug. The increase in solubility of tolnaftate with added HPBCD was found to be significantly greater than with added β-CD. For both HPBCD(A) and HPBCD(B), over the concentration range 0-0.05 M. 1:1 complexes with stability constants of 1460 ± 139 M^-1 and 1860 ± 165 M^-1 were observed, respectively. Over the β-CD concentration range 0-0.02 M, a 1:1 complex with a stability constant of 1190 ± 105 M^-1 was observed. At higher HPBCD concentrations, the increase in solubility was observed to show a positive deviation from linearity (type A_p phase diagram). Using the spectral method, in a 2 5% v/v methanol in water system, the stability constants were determined to be 1020 ± 150 M^-1 1110 ± 120 M^-1 and 1100 ± 260 M^-1 for HPBCD(A), HPBCD(B) and β-CD, respectively. The solid complexes prepared showed improved dissolution over physical mixtures and free drug.     

Comparative determination of the α/β phase fraction in α+β-titanium alloys using X-ray diffraction and electron microscopy

A comparison is made between the measured α/β phase fractions in Ti-6246 using X-ray diffraction (XRD) and electron microscopy. Image analysis of SEM and TEM images was compared to the phase fraction estimate obtained using electron backscattered diffraction, lab and high-energy synchrotron XRD. There was a good agreement between the electron microscopic and diffraction techniques, provided that the microstructural parameters of grain size and texture are estimated correctly when using quantitative Rietveld refinement.     

Study of autoabsorption for total α and β counting

The RaMsEs Group (Radioprotection et Mesures Environnementales) of the IPHC performs research and offers services mainly in the field of radioactivity measurements and sample analysis. This report will describe some of our recent experience using a semiautomatic evaporation system to prepare large area thin deposits for total α and β counting and gives experimental and simulated results for the autoabsorption coefficients.     

Amyloid Self‐Assembly of hIAPP8‐20 via the Accumulation of Helical Oligomers, α‐Helix to β‐Sheet Transition,and Formation of β‐Barrel Intermediates

The self‐assembly of human islet amyloid polypeptide (hIAPP) into β‐sheet‐rich nanofibrils is associated with the pathogeny of type 2 diabetes. Soluble hIAPP is intrinsically disordered with N‐terminal residues 8–17 as α‐helices. To understand the contribution of the N‐terminal helix to the aggregation of full‐length hIAPP, here the oligomerization dynamics of the hIAPP fragment 8–20 (hIAPP8‐20) are investigated with combined computational and experimental approaches. hIAPP8‐20 forms cross‐β nanofibrils in silico from isolated helical monomers via the helical oligomers and α‐helices to β‐sheets transition, as confirmed by transmission electron microscopy, atomic force microscopy, circular dichroism spectroscopy, Fourier transform infrared spectroscopy, and reversed‐phase high performance liquid chromatography. The computational results also suggest that the critical nucleus of aggregation corresponds to hexamers, consistent with a recent mass‐spectroscopy study of hIAPP8‐20 aggregation. hIAPP8‐20 oligomers smaller than hexamers are helical and unstable, while the α‐to‐β transition starts from the hexamers. Converted β‐sheet‐rich oligomers first form β‐barrel structures as intermediates before aggregating into cross‐β nanofibrils. This study uncovers a complete picture of hIAPP8‐20 peptide oligomerization, aggregation nucleation via conformational conversion, formation of β‐barrel intermediates, and assembly of cross‐β protofibrils, thereby shedding light on the aggregation of full‐length hIAPP, a hallmark of pancreatic beta‐cell degeneration.     

Physico-chemical study of inclusion compound Phenothiazine-β-Cyclodextrin

In this work, the authors have made many assays to prove the inclusion of phenothiazine in β-cyclodextrin.

The inclusion compound was prepared in two various ways and we have checked the inclusion using NMR and Differential Thermal Analysis tests.

This experimentation leads to other assays making inclusion compounds with molecules using the phenothiazine core and used in humans medicines.     

Superlattice stacking fault formation and twinning during creep in γ/γ′ single crystal superalloy CMSX-4

This paper describes further insight which has been gained into the formation of deformation twins during high temperature creep in a high volume fraction single crystal superalloy (CMSX-4) and correlation with the nature of superlattice stacking faults also observed. In general it is found that the formation of high temperature twinning can always be associated with the loading orientation in which SESF formation is expected from a determination of the sign of the shear stress. One can rationalise the reason for this twinning being associated with extrinsic stacking faults, by consideration of the critical radius of stacking fault loop nucleation. In particular calculations at 1223 K demonstrate a minimum in radius being associated with four overlapping faulted planes for the extrinsic case. Although the process by which twin formation occurs has not been observed, it is shown that twin formation can take place by the passage of extrinsic stacking faults within the precipitate which operate on every alternate plane of the structure. If one considers formation to occur via a pole mechanism similar to that in a face centred cubic structure a mechanism for this occurrence is postulated due to the fact that climb of the helix structure as it rotates around a pair of suitable matrix dislocations, will amount to double that which occurs in the single pole case.     

Microstructure and mechanical properties of cold-rolled TiNbTaZr biomedical β titanium alloy

The influence of the plasma-sprayed coatings and of the atmosphere on creep of the Ti–6Al–4V alloy was investigated. Yttria partially stabilized zirconia (YSZ) with CoNiCrAlY bond coat was atmospherically plasma sprayed on Ti–6Al–4V substrates. Constant load creep tests were conducted on a standard creep machine in air and nitrogen atmospheres on uncoated samples and in air on coated samples, at stress levels of 520 MPa at 500 °C, 319 MPa at 600 °C and 56 MPa at 700 °C. Results indicated that the creep rates in nitrogen and of the coated alloy were lower than those of the uncoated in air.     

γ-NaxCoO2粉体的聚丙烯酸钠凝胶法制备及其表征

本研究发展了一种用于制备氧化物热电材料γ-Na_xCoO₂粉体的化学合成方法——聚丙烯酸钠(PAAS)凝胶法。主要研究了PAAS/Co²⁺摩尔比、原料浓度和煅烧温度对产物相组成及微观形态的影响规律, 探讨了物相形成机制, 同时用该方法结合SPS制备了不同Na离子浓度的Na_xCoO₂多晶样品, 并对其热电性能进行了表征。结果表明, PAAS/Co²⁺摩尔比对产物相组成产生了显著影响, 随着PAAS/Co²⁺摩尔比的增加, 样品的相组成由Co₃O₄相向单相γ-Na_xCoO₂转变, 合适的PAAS/Co²⁺摩尔比为0.8~1.1。而反应原料浓度对产物相组成的影响存在一个临界值(0.025 mol/L), 大于临界值抑制单相形成, 小于临界值促进单相形成。煅烧温度的升高有助于γ-Na_xCoO₂单相的形成, 800℃煅烧得到γ-Na_xCoO₂单相, 晶粒形态呈片状, 平均厚度约200 nm, 片状方向的尺寸在1~4 μm之间。随着Na含量的增加, 样品的Seebeck系数增大, 电导率增加, 热导率降低, 最终导致ZT值大幅增加。     

Calculation of efficiency functions in 4π β-γ counting

An attempt is made to calculate an efficiency function applicable to 4πβ-γ coincidence measurements as the first stage of evaluating the order of the polynomial of the fitting function. For this purpose, the β-ray energy spectra and self-absorptions of spherical particle sources are calculated by the Monte Carlo simulation under the continuous slowing down approximation. On the other hand, it is shown that three sets of absorption coefficients and partial intensity ratios corresponding to a β-ray group give analytically the self-absorption for the same particle sources. Finally, we show that the efficiency functions applicable to ⁵⁹Fe and ¹³⁴Cs are easily obtained by using the energy spectra or self-absorptions.