三维结构和氧化度对C6位氧化再生纤维素止血材料性能影响

C6位氧化再生纤维素作为可吸收止血材料,其止血性能受材料理化性质的影响。通过比较氧化再生纤维素的吸水率、凝胶化速率、溶解速率、降解速率、抗老化性能和止血效果,研究三维结构和氧化度对氧化再生纤维素性能影响。结果发现,氧化度增高,氧化再生纤维素吸水率增强,凝胶化速率加快,溶解速率和降解速率变快,抗老化性能变差,产品有效期变短。纤丝松散网状多孔结构比纱布致密结构更有利于提高吸水率,加快凝胶化速率和溶解速率;同时降低氧化剂用量,提高抗老化性能。同一氧化度条件下,纤丝止血速率优于纱布,止血效果更好。     

Fabrication and characterization of superparamagnetic and thermoresponsive hydrogels based on oleic-acid-coated Fe3O4 nanoparticles, hexa(ethylene glycol) methyl ether methacrylate and 2-(acetoacetoxy)ethyl methacrylate

Stimuli-responsive hydrogel nanocomposites comprised of swollen polymer networks, in which magnetic nanoparticles are embedded, are a relatively new class of “smart” soft materials presenting a significant impact on various technological and biomedical applications. A novel approach for the fabrication of hydrogel nanocomposites exhibiting temperature- and magneto-responsive behavior involves the random copolymerization of hexa(ethylene glycol) methyl ether methacrylate (HEGMA, hydrophilic, thermoresponsive) and 2-(acetoacetoxy)ethyl methacrylate (AEMA, hydrophobic, metal-chelating) in the presence of preformed oleic-acid-coated magnetite nanoparticles (OA·Fe₃O₄). In total, two series of hydrogel nanocomposites have been prepared in two different solvent systems: ethyl acetate (series A) and tetrahydrofuran (series B). The degrees of swelling (DSs) of all conetworks were determined in organic and in aqueous media. The nanocrystalline phase adopted by the embedded magnetic nanoparticles was investigated by X-ray diffraction (XRD) spectroscopy. The obtained diffraction patterns indicated the presence of magnetite (Fe₃O₄). Deswelling kinetic studies that were carried out at ∼60 °C in water demonstrated the thermoresponsive properties of the hydrogel nanocomposites, attributed to the presence of the hexaethylene glycol side chains within the conetworks. Moreover, thermal gravimetric analysis (TGA) measurements showed that these materials exhibited superior thermal stability compared to the pristine hydrogels. Further to the characterization of compositional and thermal properties, the assessment of magnetic characteristics by vibrational sample magnetometry (VSM) disclosed superparamagnetic behavior. The tunable superparamagnetic behavior exhibited by these materials depending on the amount of magnetic nanoparticles incorporated within the networks combined with their thermoresponsive properties may allow for their future exploitation in the biomedical field.     

Analysis of Fatty Acid Ethyl Esters in Hair by Headspace Solid-Phase Microextraction (HS-SPME) and Gas Chromatography-Mass Spectrometry (GC-MS)

Abstract

Fatty acid ethyl esters (FAEE) can be used as alcohol markers in hair. The purpose of this study was to validate a new method for the detection of FAEE in hair, reducing the extraction time. Hair samples were analyzed by gas chromatography-mass spectrometry after headspace solid-phase microextraction with deuterated internal standards. Linear curves for ethyl myristate, palmitate and stearate were obtained in the range considered. The limits of detection were 0.8, 0.005, and 0.01 and the lower limits of quantification were 1.8, 0.01, and 0.4 for ethyl myristate, palmitate and stearate, respectively. Intra- and inter-assay precision and accuracy were less than 12.5% and 16.1%, respectively. Recoveries were higher than 13.5% in all cases. Finally, the method was applied to analyze hair of alcoholics, social drinkers, and teetotallers.     

Degradation Products from Naturally Aged Paper Leaves of a 16th‐Century‐Printed Book: A Spectrochemical Study

In this work, we present a wide‐range spectrochemical analysis of the degradation products from naturally aged paper. The samples obtained from wash waters used during the de‐acidification treatment of leaves from a 16th‐century‐printed book were analysed through NMR, IR, Raman UV/Vis, EPR and X‐ray fluorescence (XRF) spectroscopy and HPLC‐MS and inductively coupled plasma (ICP) analysis. By these methods we also studied some of the previous samples treated by acidification (sample AP) and catalytic hydrogenation (sample HP). Crossing all the data, we obtained precise indications about the main functional groups occurring on the degraded, water‐soluble cellulose oligomers. These results point out that the chromophores responsible for browning are conjugated carbonyl and carboxyl compounds. As a whole, we show that the analysis of wash waters, used in the usual conservation treatments of paper de‐acidification, gives much valuable information about both the conservation state of the book and the degradation reactions occurring on the leaves, due to the huge amount of cellulose by‐products contained in the samples. We propose therefore this procedure as a new very convenient general method to obtain precious and normally unavailable information on the cellulose degradation by‐products from naturally aged paper.     

pH值调控构建的纳米Ni-W催化剂用于纤维素氢解制多元醇的研究

采用等体积浸渍法制备了双金属Ni-W催化剂，并研究了制备过程中前驱体溶液pH值对活性的影响。柠檬酸和氢氧化钾分别作为酸碱调节剂将前驱体溶液pH值调节至0.83、1.00、3.09、5.00、7.03、8.97和11.0。纤维素氢解反应结果表明，当前驱体溶液的pH值为1.00时，在氢压为5.0 MPa、温度为518 K的反应条件下，得到低碳（C_2，3）多元醇的总收率为74.5%。此外，通过BET和SEM表征了催化剂的物理性质。其比表面积为330-450 m²/g，且在高温煅烧下SBA-15仍保持良好的水热稳定性。TEM和SEM-EDX结果显示，催化剂粒子在载体表面分散性较好，但也有少量的聚集现象。XRD表征表明，NiO等物种的还原程度明显受到pH值的影响，且镍、钨物种的相态也存在着显著不同。     

Impact of cellulose nanocrystal aspect ratio on crystallization and reinforcement of poly(butylene adipate‐co‐terephthalate)

Cellulose nanocrystals (CNCs) are appealing nanomaterials for the reinforcement of polymeric materials. It is now well established that high mechanical properties are obtained when preparing the nanocomposite by casting/evaporation methods and using CNC contents above the percolation threshold. This phenomenon results from the formation of a stiff CNC network within the matrix meaning that the properties of the matrix play only a limited role on the mechanical properties of the material when the matrix is in the rubbery state. In subpercolation concentration or when using a different processing technique, the level of understanding is less clear, mainly when the CNC‐induced crystallization of the matrix interferes with the reinforcing mechanism. In this study, we used CNCs with different aspect ratios to prepare nanocomposites by extrusion with polybutyrate adipate terephthalate as matrix. The impact of CNC on the crystallinity of the matrix and mechanical properties of the nanocomposite has been investigated. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 2284–2297     

Synergistic effect of cellulose nanowhiskers reinforcement and dicarboxylic acids crosslinking towards polyvinyl alcohol properties

In the presented work, a significant increase in the tensile strength of the PVA composite material is reported. The obtained best value of 122 MPa and 14.6% swelling shows the excellent synergistic effect of both crosslinker and reinforcement material. The composite films were prepared by simple mechanical dispersion of reinforcement material, bacterial cellulose nanowhiskers (BCNW) into PVA solution followed by crosslinking with diacids, succinic acid (SuA), and adipic acid (AdA). The effect of aliphatic carbon chain length of crosslinker on thermal, mechanical, and water uptake properties is evaluated and discussed in detail. Neat PVA had the strength of 37.3 MPa. With 5% reinforcement of BCNW, that is, without crosslinking, it exhibited 97% increase, that is, 74.5 MPa. With crosslinking of 15 mmol of SuA and AdA PVA films for 2 h had excellent thermal properties with swelling percentage of 19 and 26.6% and tensile strength of 103 and 67 MPa, respectively. The best result obtained was for 5% BCNW–PVA films crosslinked with 15 mmol SuA. These results were explained on the basis of synergetic crosslinking and extended hydrogen bonding between PVA and reinforcement material. The composite films can be used as biological implants, a membrane for pervaporation and filtration system, etc. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 2515–2525     

The performance of 1‐ethyl‐3‐methylimidazolium tetrafluoroborate ionic liquid as mobile phase additive in HPLC‐based lipophilicity assessment

Ionic liquids have been widely used as green alternative mobile phase additives to shield the residuals silanols groups and modify the stationary/mobile phase HPLC systems. The present study aimed to evaluate the performance of the ionic liquid 1‐ethyl‐3‐methylimidazolium tetrafluoroborate ([EMIM][BF4]) in producing extrapolated logk_w indices suitable to substitute for octanol–water logP or logD values. The effect of [EMIM][BF4] was investigated for a set of basic and neutral drugs using two different columns, BDS and ABZ⁺. [EMIM][BF4] was added simply alone or in combination with n‐octanol and was compared with the conventional masking agent n‐decylamine. [EMIM][BF4] reduced the retention by suppressing silanophilic interactions, althoug to a lower extent than n‐decylamine. Addition of n‐octanol further decreased the retention by shielding silanol sites on BDS and/or interacting with polar groups through hydrogen bonding on ABZ⁺. Logk_w/logD_7.4 relationships proved moderate compared with those derived upon addition of n‐decylamine. They were considerably improved upon the introduction of protonated fraction F⁺ in the correlation, reflecting ion pair formation between the chaotropic anion [BF4]^‐ and the protonated basic compounds. In this aspect, the ionic liquid [EMIM][BF4], although efficient as a masking agent, cannot be recommended as mobile phase additive to reproduce octanol–water partitioning. Copyright © 2010 John Wiley & Sons, Ltd.     

Determination of ethyl glucuronide and fatty acid ethyl esters in hair samples

Hair testing for alcohol biomarkers is an important tool for monitoring alcohol consumption. We propose two methods for assessing alcohol exposure through combined analysis of ethyl glucuronide (EtG) and fatty acid ethyl esters (FAEEs) species (ethyl myristate, palmitate, stearate and oleate) in hair (30 mg). EtG was analysed by liquid chromatography–tandem mass spectrometry, while FAEEs were analysed by gas chromatography–tandem mass spectrometry using electron impact ionization. Both methods were validated according to internationally accepted guidelines. Linearity was proven between 3 and 500 pg/mg for EtG and 30–5000 pg/mg for FAEEs, and the limits of quantification were 3 pg/mg for EtG and 30 pg/mg for each of the four FAEEs. Precision and accuracy were considered adequate, processed EtG samples were found to be stable for up to 96 h left in the injector and processed FAEEs samples for up to 24 h. Matrix effects were not significant. Both methods were applied to the analysis of 15 authentic samples, using the cut‐off values proposed by the Society of Hair Testing for interpretation. The results agreed well with the self‐reported alcohol consumption in most cases, and demonstrated the suitability of the methods to be applied in routine analysis of alcohol biomarkers, allowing monitoring consumption using low sample amounts.