Thermally Responsive Reversed Micelles for Immobilization of Enzymes

In this study, thermally responsive alkyl end‐capped poly(N‐isopropylacrylamide‐co‐acrylic acid) amphiphilic copolymers were synthesized, and successfully utilized to fabricate reversed micelles and immobilize enzymes. Transmission electron microscopy (TEM) study showed that the reversed micelles were spherical in nature. The activity of Candida rugosa lipase immobilized in the reversed micelles towards catalyzing the esterification of lauric acid and 1‐propanol was analyzed in comparison with naked enzyme. Immobilized lipase provided much greater catalytic activity. In addition, the effects of pH, water content, polymer and enzyme concentration on the catalytic activity were investigated. The optimized fabrication conditions of lipase‐loaded reversed micelles, under which lipase gave the highest activity, were as follows: polymer concentration, 12 mg mL^–1; enzyme concentration, 25 mg mL^–1 phosphate buffered saline (PBS); pH, 7.4; W₀ ([water]/[surfactant]), 83.3. Lipase immobilized in these micelles was much more stable than that in conventional sodium bis(2‐ethylhexyl) sulfosuccinate micelles. More importantly, the size of lipase‐immobilized micelles decreased, and the enzyme solution precipitated from the reaction mixture when the temperature increased to a value slightly higher than the lower critical solution temperature (LCST) of the polymer. The recovery rate of enzyme was about 75 %. The α‐helix structure of the recovered lipase remained intact. In addition, the enzymatic reaction was terminated after raising the environmental temperature slightly above the LCST. These thermally responsive micelles may make a promising system for enzyme immobilization.     

基于分级磁阀结构的三相磁控电抗器谐波抑制研究

为了降低磁控电抗器MCR产生的谐波对电网的影响,笔者提出将MCR工作铁心设计为分级磁阀结构,并建立了这种铁心结构的磁路等效数学模型。在分析一般磁控电抗器谐波分布特性的基础上,给出了分级磁阀结构电抗器的谐波抵消原理。计算结果表明分级磁阀结构电抗器将现有MCR半极限饱和条件下输入电网的最大谐波电流含量由6%降低到3%。     

A redox poly(ionic liquid) hydrogel: Facile method of synthesis and electrochemical sensing

In this article, a redox-responsive poly(ionic liquid) (redox-PIL) hydrogel Poly(1-vinyl-3-propionate imidazole phenothiazine sulfonic acid)-chitosan [Poly(VPI⁺PTZ-(CH₂)₃SO₃⁻)-CS] was produced by using chitosan (CS) crosslinking with redox-PIL Poly(1-vinyl-3-propionate imidazole phenothiazine sulfonic acid [Poly(VPI⁺PTZ-(CH₂)₃SO₃⁻)]. The incorporation of redox-active counter anions 3-(phenothiazine-10-yl) propane 1-sulfonic acid anions (PTZ-(CH₂)₃SO₃⁻) into cationic PIL-polyimidazole rendered Poly(VPI⁺PTZ-(CH₂)₃SO₃⁻) with electron catalytic ability, ionic conductivity, and electron conductivity. Poly(VPI⁺PTZ-(CH₂)₃SO₃⁻)-CS combines the properties of hydrogel and redox-PIL, thus offering intrinsic porous conducting frameworks and promoting the transport of charges, ions, and molecules, leading hydrogel with excellent electrochemical properties. The crosslinking occurrence of Poly(VPI⁺PTZ-(CH₂)₃SO₃⁻) and CS resulting from the synthetic process of hydrogel was verified by differential scanning calorimetry and thermogravimetric analysis. A three-dimensional polymer network hydrogel with good biocompatibility and permeability was formed after crosslinking. In addition, only 64% weight loss within 600 °C was observed in Poly(VPI⁺PTZ-(CH₂)₃SO₃⁻)-CS representing its thermally stable performance. When used as an electrochemical sensor, the hydrogel-modified gold electrode improved the electrocatalytic oxidation of cysteine. Differential pulse voltammetry results indicated that the detection range was from 5 × 10⁻⁸ to 5 × 10⁻³ M and the limit of detection was 6.64 × 10⁻⁸ M. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48051.     

Drug release kinetics of pH-responsive microgels of different glass-transition temperatures

The pH-responsive microgels (MGs) consisting of methacrylic acid-ethyl acrylate (MAA-EA), methacrylic acid-butyl methacrylate (MAA-BMA) or methacrylic acid-methyl methacrylate (MAA-MMA) crosslinked with di-allyl phthalate (DAP) were synthesized via emulsion polymerization. It was found that the energy required to extract a proton from MGs with higher glass-transition temperature (T_g) was greater than at a lower T_g. Procaine hydrochloride (PrHy) was used to study the release of a model hydrophobic drug from MGs with different T_gs. A drug selective electrode (DSE) was used to monitor the release as a function of pHs and T_gs. With increasing pH or decreasing T_g, the swelling of MGs was enhanced, leading to greater release of the drug. From the Berens and Hopfenberg model, the contributions of chain relaxation and diffusion processes during a release process were determined. The drug release from lower T_g MGs and at high pH is dominated by diffusion rather than chain relaxation. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47284.     

富含鼠尾草酸液态提取物的制备工艺研究

通过响应面分析优化了富含鼠尾草酸液态提取物制备工艺条件.结果表明,其最优工艺条件为:乙醇浓度为60%,油水比例为7.6,旋转浓缩温度为65℃,上述工艺条件下提取鼠尾草酸含量为14.91%.抗氧化实验结果表明该提取物具有良好的油脂抗氧化活性.     

Informative and corrective responsive packaging: Advances in farm-to-fork monitoring and remediation of food quality and safety

Microbial growth and fluctuations in environmental conditions have been shown to cause microbial contamination and deterioration of food. Thus, it is paramount to develop reliable strategies to effectively prevent the sale and consumption of contaminated or spoiled food. Responsive packaging systems are designed to react to specific stimuli in the food or environment, such as microorganisms or temperature, then implement an informational or corrective response. Informative responsive packaging is aimed at continuously monitoring the changes in food or environmental conditions and conveys this information to the users in real time. Meanwhile, packaging systems with the capacity to control contamination or deterioration are also of great interest. Encouragingly, corrective responsive packaging attempting to mitigate the adverse effects of condition fluctuations on food has been investigated. This packaging exerts its effects through the triggered release of active agents by environmental stimuli. In this review, informative and corrective responsive packaging is conceptualized clearly and concisely. The mechanism and characteristics of each type of packaging are discussed in depth. This review also summarized the latest research progress of responsive packaging and objectively appraised their advantages. Evidently, the mechanism through which packaging systems respond to microbial contamination and associated environmental factors was also highlighted. Moreover, risk concerns, related legislation, and consumer perspective in the application of responsive packaging are discussed as well. Broadly, this comprehensive review covering the latest information on responsive packaging aims to provide a timely reference for scientific research and offer guidance for presenting their applications in food industry.     

Dual pH‐ and thermal‐responsive nanocomposite hydrogels for controllable delivery of hydrophobic drug baicalein

Hydrogels have been widely used as mild biomaterials due to their bio‐affinity, high drug loading capability and controllable release profiles. However, hydrogel‐based carriers are greatly limited for the delivery of hydrophobic payloads due to the lack of hydrophobic binding sites. Herein, nano‐liposome micelles were embedded in semi‐interpenetrating poly[(N‐isopropylacrylamide)‐co‐chitosan] (PNIPAAm‐co‐CS) and poly[(N‐isopropylacrylamide)‐co‐(sodium alginate)] (PNIPAAm‐co‐SA) hydrogels which were responsive to both temperature and pH, thereby establishing tunable nanocomposite hydrogel delivery systems. Nano‐micelles formed via the self‐assembly of phospholipid could serve as the link between hydrophobic drug and hydrophilic hydrogel due to their special amphiphilic structure. The results of transmission and scanning electron microscopies and infrared spectroscopy showed that the porous hydrogels were successfully fabricated and the liposomes encapsulated with baicalein could be well contained in the network. In addition, the experimental results of response release in vitro revealed that the smart hydrogels showed different degree of sensitiveness under different pH and temperature stimuli. The results of the study demonstrate that combining PNIPAAm‐co‐SA and PNIPAAm‐co‐CS hydrogels with liposomes encapsulated with hydrophobic drugs is a feasible method for hydrophobic drug delivery and have potential application prospects in the medical field. © 2018 Society of Chemical Industry