Facile fabrication of tough and biocompatible hydrogels from polyvinyl alcohol and agarose

A polyvinyl alcohol (PVA)-agarose (agar) composite hydrogel (M-PVA-agar-60) was developed by simple three cycles of freeze-thawing, followed by successively soaking in ammonium sulfate aqueous solution to induce phase separation and dialyzing against deionized water to remove residual sulfate salts. Due to the synergy of crystalline regions, hydrogen bonding and phase separation domains, the obtained M-PVA-agar-60 hydrogel exhibits excellent mechanical properties (tensile strength = 1.1 MPa, tensile strain = 324% and compressive stress = 12.5 MPa), combined with a high water content of 87.0%. Moreover, the hydrogel hardly expands after immersing in the phosphate-buffered saline aqueous solution at 37°C for a week, and the tensile stress and toughness remain almost the same as their initial values, superior to most reported non-swellable hydrogels. Because of the biocompatible starting materials, absence of toxic chemicals, and dialysis in advance to remove ammonium sulfate, the hydrogel also shows excellent cell compatibility, making it an ideal candidate for tissue engineering materials.     

Application of high‐pressure homogenization on gums

High‐pressure homogenization (HPH) is an emerging process during which a fluid product is pumped by pressure intensifiers, forcing it to flow through a narrow gap, usually measured in the order of micrometers. Gums are polysaccharides from vegetal, animal or microbial origin and are widely employed in food and chemical industries as thickeners, stabilizers, gelling agents and emulsifiers. The choice of a specific gum depends on its application and purpose because each form of gum has particular values with respect to viscosity, intrinsic viscosity, stability, and emulsifying and gelling properties, with these parameters being determined by its structure. HPH is able to alter those properties positively by inducing changes in the original polymer, allowing for new applications and improvements with respect to the technical properties of gums. This review highlights the most important advances when this process is applied to change polysaccharides from distinct sources and molecular structures, as well as the future challenges that remain. © 2017 Society of Chemical Industry     

Microwave‐assisted synthesis of chitosan biguanidine hydrochloride and its antioxidant activity in vitro

Chitosan biguanidine hydrochloride (CSGH) was synthesized by guanidinylation of chitosan hydrochloride (CSH) under microwave irradiation and characterized by Fourier transform infrared spectroscopy, gel permeation chromatography, and element analysis. The antioxidant activity of CSGH was evaluated by both chemical and cellular methods. The results showed that CSGH was better than CSH but slightly inferior to ascorbic acid (Vc) for scavenging 2,2‐diphenyl‐1‐picryl‐hydrazyl (DPPH) free radicals, and the DPPH? scavenging ability of CSGH was dose‐dependent. However, cell experiments indicated CSGH had a superior repairing effect on oxidatively damaged cells. The intervention of CSGH could excellently recover the cell morphology, decrease the level of malondialdehyde, and enhance the activity of superoxide dismutase and glutathione peroxidase. CSGH could be a potential antioxidant reagent, and its antioxidant activity was reflected not only in scavenging the free radicals but also in regulating the oxidation/antioxidation balance of damaged cells. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43570.     

A Review on the Structure-Function Relationship Aspect of Polysaccharides from Tea Materials

Tea (Camellia sinensis) has a long history of medicinal use in the world. The chemical components of tea mainly consist of polyphenols (TPP), proteins, polysaccharides (TPS), chlorophyll, alkaloids, and so on. Great advances have been made in chemical and bioactive studies of catechins and TPP from tea in recent decades. However, the TPS from tea materials have received much less consideration than that of TPP. The number of relevant publications on the TPS from tea leaves and flowers has increased rapidly in recent years. This mini-review summarizes the structure-function relationship of TPS from tea leaves and flowers. The application of purified TPS from tea material as functional or nutritional foods was still little. It will help to develop the function foods with tea TPS and better understand the structure–bioactivity relationship of tea TPS.     

In vitro and In vivo studies on intragastric soya protein–polysaccharide gels in a beverage matrix

Intragastric gelation is a mechanism whereby a consumed liquid food gels under the acidic gastric condition. It was hypothesised that intragastric gelation would result in satiety due to delayed gastric emptying. Three treatment beverages that is soya protein isolate (SPI) with λ‐carrageenan (SPI‐LC; high viscosity, gelling), guar gum (SPI‐GG; high viscosity) and no polysaccharide (SPI; low viscosity) were given to twenty participants in a randomised 3 × 3 double‐blind within‐subject crossover design trial and asked to rate their hunger and fullness scores (visual analogue scale; VAS) before and up to 60 min after consumption of the beverage. Results show that there were no significant effects on hunger, fullness and energy intake after consuming the SPI‐LC (gelling) beverage compared to the SPI‐GG beverage, but did evoke weak satiety signals up to 20 min after consumption when compared to the control (low‐viscosity) SPI beverage. Therefore, intragastric gelation does not result in satiety in this study.     

Effect of surface acetylated‐chitin nanocrystals on structure and mechanical properties of poly(lactic acid)

In this work, the miscibility between chitin nanocrystals (ChNs) and poly(lactic acid) (PLA) was expected to be improved by surface acetylation of ChN. The reaction of acetic anhydride onto the ChN surface was confirmed by FTIR and ¹³C NMR, while XRD and TEM proved the crystalline structure and rod‐like morphology were maintained. The acetylated ChN (AChN) was incorporated into a PLA matrix by solution blending, and resulted in an increase of tensile strength and Young's modulus and they reached to the maximum value as 45 and 37% higher than neat PLA film, respectively, with the loading level of AChN reaching to 4 wt %. The enhancement could be attributed to that acetylation improved dispersion of AChN in the PLA matrix and interfacial adhesion between AChN and PLA. The performances of the nanocomposites based on PLA and chitin nanocrystals derived from renewable resources have good potential for industrial applications. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39809.     

Adsorption and desorption of zinc(II) on water‐insoluble starch phosphates

Water‐insoluble starch phosphates (SPs) with different contents of phosphate groups were used as adsorbents of Zn(II). The effects of the adsorption time, dosage of adsorbents, and pH on the removal of Zn(II) by SPs were thoroughly studied. The results showed that the water‐insoluble SPs were effective adsorbents for Zn(II) removal. The optimal adsorption effect was achieved at pH = 4.0, and the adsorption equilibrium data agreed well with the Langmuir isotherm model with a maximum adsorption capacity of 2.14 mmol/g. Furthermore, the desorption process and reusability of the adsorbents were studied. HCl (0.5N) was found to be an appropriate desorption solution to desorb Zn(II) ions from the adsorbents. After three adsorption/desorption cycles, the Zn(II) adsorption capacities of three SP samples decreased from 0.92, 1.23, and 1.44 to approximately 0.72, 1.02, and 1.29 mmol/g, respectively, and all the desorption percentages were greater than 93%. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

野生拳菜多糖的提取工艺及其抗氧化性研究

研究野生拳菜多糖的提取工艺和抗氧化性.在单因素试验基础上,采用正交试验得出野生拳菜多糖的适宜工艺条件,即提取温度90℃,提取时间100 min,料液比1∶70.在此提取工艺条件下,拳菜多糖的含量达到23.07％.体外抗氧化实验表明:拳菜粗多糖有较强的抗氧化性,对DPPH·的清除率可达到70.58％.对拳菜粗多糖的分离纯化结果表明拳菜粗多糖含有两个分子量的多糖组分.