Synthesis and Properties of IPN Hydrogels Based on Konjac Glucomannan and Poly（acrylic acid）

As a random copolymer of β-(1,4) linked D-mannose and D-glucose, konjac gluco- mannan (KGM) is a naturally occurring water-soluble polysaccharide, and has been paid attention in the field of drug controlled release carriers potentially used in colon1,2. …     

A Review of the Development of Properties and Structures Based on Konjac Glucomannan as Functional Materials

In recent years, konjac glucomannan(KGM) has gained considerable attention due to its non-toxic, harmless, excellent biocompatibility, biodegradability, good water imbibition as well as gel properties. KGM and its derivatives have been widely used in food science, chemical, pharmaceutical, and material areas. In this review, we will focus on the most recent advances in the structures and properties of KGM. We will first describe the influence of different modification methods on the structures and properties of KGM. Then we will review the results obtained with KGM as functional materials in different studies in the fields of hydrogels, aerogels, nanoparticles, membrane materials, microspheres and microcapsule to provide theoretical basis for the further study.     

酶催化魔芋葡甘聚糖的可控降解

魔芋葡甘聚糖 (KGM)是一种来自植物的天然高分子 .它具有优异的可生物降解性和生物相容性 ,并具有许多独特的生理和药理功能 .本实验首先测定了 β 甘露糖酶在不同条件 (温度、pH值、介质 )下的活性 ,发现 β 甘露糖酶在 5 0℃左右 ,pH 9 4附近 ,乙醇含量低于 5 %的水介质中具有较高的活力 ;而在pH 7 0以下 ,或温度低于 3 0℃ ,或加入 2 0 %乙醇的条件下均基本上失活 .在此研究基础上 ,探讨了 β 甘露糖酶催化KGM降解反应的规律 ,通过调节反应条件制备了一系列分子量不同的降解样品 ,并确定了KGM的分子量与特性粘数之间的关系为 :[η]=5 0 6× 1 0 - 4M0 754w ,使得酶催化KGM的可控降解成为可能 ,从而为深入研究KGM及其衍生物的结构与性能 ,扩展其应用领域奠定了良好的理论和实验基础     

CHARACTERIZATION OF POLY(VINYL ALCOHOL)-KONJAC GLUCOMANNAN BLEND FILMS

This article deals with the characterization of blend films obtained by mixing poly(vinyl alcohol) (PVA) and konjac glucomannan (KGM) in aqueous solution. The DTA curves of PVA/KGM blend films showed overlapping of the main thermal transitions characteristic of the individual polymers. The exothermic peak at 312°C, which resulted from the thermal degradation of the KGM, shifted slightly to a higher temperature at low PVA content (≤20 wt%). The weight-retention properties of the blend films indicated that thermal stability of the blend films were better than pure KGM film at PVA content below 20 wt%. The crystallinities, tensile strength, and elongation at break of the films increased with the PVA content, and reached the maximum values at 20 wt% PVA, then decreased. Changes in the carbonyl stretching band of KGM and hydroxyl stretching regions of KGM and PVA were detected by FTIR analysis. Those are attributable to the existence of a certain degree of inteaction between KGM and PVA, and resulted from intermolecular hydrogen bonds. Phase separation phenomena were observed by examining the surface of the blend films by SEM.     

高取代度魔芋葡甘聚糖醋酸酯的制备及其热塑性和流变性研究

以魔芋葡甘聚糖(KGM)为原料,浓硫酸为催化剂,乙酸酐为改性剂,制备了KGM醋酸酯.研究了反应条件对KGM醋酸酯取代度(DS)的影响,KGM醋酸酯制备的最佳反应条件是乙醇∶水量比5∶5,反应时间2h,反应温度75℃,催化剂浓硫酸的浓度0.1mol/L,KGM与乙酸酐的量比5∶40(g/mL),取代度高达2.93,其分子量与KGM相比,则明显降低.运用傅立叶红外光谱仪(FTIR)、X射线衍射仪(XRD)、扫描电镜(SEM)、热重分析仪(TGA)、示差扫描量热仪(DSC)和旋转流变仪对KGM和高取代度KGM醋酸酯进行了表征.结果表明,KGM醋酸酯的羰基(CO)特征吸收峰较KGM明显增强,其表观形貌大部分为疏松絮状,KGM及其醋酸酯均为非晶态结构.与KGM相比,KGM醋酸酯的热稳定性下降,分解温度(Td)由KGM的261.10℃降低至KGM醋酸酯的204.56℃,KGM醋酸酯出现了明显的玻璃化转变,其玻璃化转变温度(Tg)为128.49℃.KGM醋酸酯是典型的黏弹性材料,其弹性比率占21.27%,其剪切黏度η对温度变化非常敏感,可通过温度的改变来调节KGM醋酸酯的加工流动性.KGM醋酸酯具有较好的热塑性.     

干燥方式对含直链淀粉半互穿网络水凝胶溶胀和降解的影响

以4,4′-二甲基丙烯酰胺基偶氮苯(BMAAB)为交联剂,制备了丙烯酸-丙烯酰胺-甲基丙烯酸酯共聚物和直链淀粉半互穿网络水凝胶.以冷冻干燥和空气干燥两种方式,研究了干凝胶在pH2.2和pH7.4时的溶胀和降解性能.结果表明采用两种干燥方式的凝胶在不同pH的介质中都遵循二级溶胀动力学.凝胶内部水的扩散均为非Fickian机理,即扩散和链松弛协同作用的机理.但经历冷冻干燥的凝胶其扩散机制占优势.在pH=7.4的介质中,冷冻干燥凝胶的平衡溶胀比(SR)显著增大,而在pH=2.2时则无明显变化.扫描电镜(SEM)和降解实验发现,在结肠内容物的作用下,冷冻干燥凝胶在5天内降解率可达35.3%,而空气干燥凝胶的降解率为28.1%,表明冷冻干燥的方式可在一定程度上促进凝胶在结肠环境下的降解.     

Diselenide-containing poly(ε-caprolactone)-based thermo-responsive hydrogels with oxidation and reduction-triggered degradation

Herein, novel multi-responsive injectable polyester hydrogels were reported based on the diselenide-containing poly(ε-caprolactone) copolymers ((mPEG-PCL-Se)₂). The (mPEG-PCL-Se)₂ solution remained a free-flowing state at ambient temperature but spontaneously turned into a semisolid hydrogel upon heating to physiologic temperature. The phase transition temperature was examined to be dependent on the composition and aqueous concentration of the copolymers. More importantly, the thermo-responsive hydrogels were endowed with oxidation and reduction-triggered degradation by the incorporation of diselenide groups. Accordingly, the degradation of poly(ε-caprolactone)-based hydrogels was greatly improved and the rate of degradation was well regulated by the concentration of hydrogen peroxide (H₂O₂) or glutathione (GSH). This superior stimuli-responsive degradation could lead to an enhanced drug release of encapsulated drug (Doxorubicin, DOX). Thus the oxidation and reduction-triggered degradable diselenide-containing poly(ε-caprolactone) hydrogels would offer great potential for the controlled drug delivery.     

Molecular weight effects on gelation and rheological properties of konjac glucomannan–xanthan mixtures

Fractions of konjac glucomannan (KGM) with various viscosity‐average molecular weights (M_v) ranging from 4.00 × 10⁵ to 2.50 × 10⁶ were prepared by hydrolysis degradation in hydrochloride acid/ethanol. Effect of M_v of KGM on the critical gelation temperature (T_gel) determined by Winter–Chambon criterion and the elasticity of KGM/xanthan mixed gels, a kind of binary gel formed by synergistic gelation, were investigated by dynamic viscoelastic measurements. It was shown that the value of T_gel of the gel was shifted to a higher temperature and the gel strength was enhanced when M_v of KGM was increased. The critical M_v (1.91 × 10⁶) was observed, above which the T_gel and elasticity of the mixed gels showed no or slight increase. It was suggested that T_gel and elasticity of KGM/xanthan mixed gels mainly depend on the structure of junction zones driven by the strong interaction between KGM and xanthan, which was gradually improved with increasing M_v of KGM. It was found that the critical strain and yield stress of the mixed gels increased monotonically with the increasing M_v of KGM. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 313–321, 2010     

Preparation and controlled degradation of oxidized sodium alginate hydrogel

Degradation is often a critical property of materials utilized in tissue engineering. Although alginate, a naturally derived polysaccharide, is an attractive material due to its biocompatibility and ability to form hydrogels, its slow and uncontrollable degradation can be an undesirable feature. In this study, the degradation behavior of hydrogel based on oxidized sodium alginate (OSA) crosslinked with Ca²⁺ was studied in phosphate buffer solution (PBS, pH = 7.4) and Tris-(hydroxymethyl) aminomethane–HCl (Tris–HCl, pH = 7.4) at 37 °C. The degradation behavior of OSA hydrogels with different degrees of oxidation was evaluated as a function of degradation time by monitoring the changes of molecular weight and weight loss. It was found that the degradation behavior relied heavily on the degree of oxidation and the surrounding medium. This result indicates that the degradation rates of OSA hydrogels can be controlled by changing the degree of oxidation.     

Preparation,Structures and Mechanical Properties of Bamboo Shoot Shell Nanofiber/Konjac Glucomannan Aerogels

With bamboo shoot shell nanofibers(BSN) and konjac glucomannan(KGM) as precursor materials, the BSN/KGM aerogels were prepared in different proportions by sol-gel method. The surface morphology, microstructure, characteristic functional groups and thermal properties of BSN/KGM aerogels were characterized by scanning electron microscopy(SEM), infrared spectroscopy(IR), X-ray diffraction(XRD) and thermogravimetric analysis(TGA). The effect of BSN on the structure and properties of BSN/KGM aerogels was also studied. The results showed that the BSN/KGM aerogels possessed network porous structure with compact and homogeneous porosity, high specific surface area and low density. With the increase of BSN, the sheet structure of aerogels was converted into the 3D porous network structure, which contributes significantly higher thermal stability. In addition, the BSN/KGM aerogels showed excellent mechanical properties. The maximum relative compression rate was 62%, suggesting the addition of BSN can enhance the compression properties of the BSN/KGM aerogels.     

Study on the Epigallocatechin Gallate and Konjac Glucomannan Mosaic Topological Structure

In order to effectively protect the activity of Epigallocatechin gallate(EGCG), we explored the protection mechanism of Konjac glucomannan(KGM) for EGCG by experiments and theory analyses. We synthesized KGM/EGCG nanofibers by using electrostatic spinning method. The microstructure of nanofibers was characterized by SEM, FTIR, TGA, XRD and Raman spectroscopic. The formation mechanism and the protection effects of KGM/EGCG nanofibers were also discussed. The results showed that the EGCG activity was protected due to the hydrogen bonds between-OH of EGCG and KGM, and EGCG was embedded in KGM nanofiber with bead style. The reducing force and DPPH scavenging ability data indicated that KGM/EGCG nanofibers have stronger antioxidant activity than the EGCG solution under the same condition. Hence, the mosaic topological structure of KGM can effectively extend the EGCG activity.     

Biodegradation of random co-polypeptide hydrogels consisting of N-hydroxypropyl l-glutamine as one component

Two component random co-polypeptide hydrogels consisting of N-hydroxypropyl l-glutamine and l-alanine (Ala) or l-phenylalanine (Phe) were prepared by performing aminolysis reactions with 3-amino-1-propanol together with crosslinking reaction with 1,8-octamethylenediamine on hydrogels of the starting co-polymers consisted of γ-benzyl l-glutamate and Ala or Phe. The relationship between their bulk structure and properties was evaluated with regard to the swelling ratio in water (q), the rate of water vapor permeability (V_f), tensile properties, and enzymatic degradation behaviors of hydrogels in a pseudo-extracellular fluid (PECF). The tensile property of the hydrogels was highly dependent on q in PECF, and on the hydrophobicity of the side chains. A relationship was obtained between the V_f and q of hydrogels in PECF regardless of the differences in the nature of the side chains. Biodegradation of the hydrogels in vitro by bromelain indicated that degradation took place in bulk rather than on the surface, and that the rate of degradation was also highly dependent on q in the samples as well as on the hydrophobicity of the side chains of the samples.     

Doublestimuli-responsive degradable hydrogels for drug delivery: Interpenetrating polymer networks composed of oligopeptide-terminated poly(ethylene glycol) and dextran

Biodegradable hydrogels composed of oligopeptide-terminated poly(ethylene glycol) (PEG) and dextran with interpenetrating polymer network (IPN) structure were proposed as a novel substrate for multistimuli-responsive drug delivery. IPN-structured hydrogels were synthesized by sequential crosslinking reactions of N-methacryloyl-glycilglycilglycil-terminated PEG and dextran. In vitro degradation of the IPN-structured hydrogels was examined using papain and dextranase as model enzymes for hydrolyzing the oligopeptide and the dextran. Specific degradation in the presence of papain and dextranase was observed in the IPN-structured hydrogel with a particular composition of PEG and dextran, whereas this hydrogel was not degraded by one of the two enzymes.     

分子量及酰基供体对酶促魔芋葡甘聚糖酰化反应的影响

研究了在有机介质叔丁醇中魔芋葡甘聚糖(KGM)的分子量及酰基供体对固定化脂肪酶Novozym 435催化KGM乙酰化反应的影响.KGM的分子量对酶促其酰化反应的活性及产物取代度有显著影响.随着KGM分子量的增大,酶催化反应的速率逐渐下降,产物的取代度逐渐减小.KGM分子量对该反应的影响与不同分子量KGM的溶解度、体系粘度、空间位阻及颗粒形态等因素有关.以不同链长的脂肪酸乙烯酯为酰基供体时,随着酰基供体中脂肪酸碳链的增长,酶促KGM酰化反应速率逐渐下降,产物的取代度逐渐减小,且该酰化反应具有高度的区域选择性,反应均发生在C6-OH上.     

魔芋葡甘聚糖／SiO2纳米复合物的制备与表征

用纳米SiO2为原料,以魔芋葡甘聚糖(KGM)为基体,采用共混法制得KGM/SiO2纳米复合物。通过傅立叶红外光谱(FTIR)、热重分析(TG)、透射电镜(TEM)等手段对该体系进行了表征。结果表明:由于纳米SiO2粒子的引入,KGM分子FTIR的某些特征峰的波数发生明显变化;纳米SiO2在复合物中的分散性较好;复合材料的热稳定性高于KGM薄膜;此外,复合材料的力学性能有所提高。     

Novel poly(amido-amine)-based hydrogels as scaffolds for tissue engineering

Biodegradable and biocompatible amphoteric poly(amido-amine) (PAA)-based hydrogels, containing carboxyl groups along with amino groups in their repeating unit, were considered as scaffolds for tissue engineering applications. These hydrogels were obtained by co-polymerising 2,2-bisacrylamidoacetic acid with 2-methylpiperazine with or without the addition of different mono-acrylamides as modifiers, and in the presence of primary bis-amines as crosslinking agents. Hybrid PAA/albumin hydrogels were also prepared. The polymerisation reaction was a Michael-type polyaddition carried out in aqueous media. The PAA hydrogels were soft and swellable materials. Cytotoxicity tests were carried out by the direct contact method with fibroblast cell lines on the hydrogels both in their native state (that is, as free bases) and as salts with acids of different strength, namely hydrochloric, sulfuric, acetic and lactic acid. This was done in order to ascertain whether counterion-specific differences in cytotoxicity existed. It was found that all the amphoteric PAA hydrogels considered were cytobiocompatible both as free bases and salts. Selected hydrogels samples underwent degradation tests under controlled conditions simulating biological environments, i.e. Dulbecco medium at pH 7.4 and 37 degrees C. All samples degraded completely and dissolved within 10 d, with the exception of hybrid PAA/albumin hydrogels that did not dissolve even after eight months. The degradation products of all samples turned to be non-cytotoxic. All these results led us to conclude that PAA-based hydrogels have a definite potential as degradable matrices for biomedical applications.     

Synthesis and degradation of intelligent hydrogels containing polyacetal segments

Intelligent hydrogels were first obtained by copolymerization of telechelic poly(1,3-dioxolane) (pDXL) with acrylic acid, acrylamide, N-isopropylacrylamide respectively. The synthesis and characterization of the networks were discussed. The swelling behavior of the hydrogel was dependent on the solubility parameter of the solvents and hydrogels. The networks containing polyacetal segments (pDXL) can degrade by acid in different solvents. DXL and few other cycle molecules measured by GC-MS analysis were formed after degradation. According to the degradation products, the polymerization mechanism can be testified.     

Preparation and characterization of hydrogels based on acryloyl end-capped four-arm star-shaped poly(ethylene glycol)-branched-oligo(<Emphasis Type="SmallCaps">l</Emphasis>-lactide) via Michael-type addition reaction

An acryloyl end-capped four-arm star-shaped poly(ethylene glycol)-branched-oligo(l-lactide) (4A-PEG-PLA) macromer was firstly prepared. A novel kind of hydrogels was synthesized via the Michael-type addition reaction between (2S,3S)-1,4-bis-sulfanylbutane-2,3-diol (dithiothreitol) and this macromer. Gelation time was determined visually as the time when the precursor solution did not flow on inverting the vials. Hydrogel structure was characterized by FTIR analysis, swelling and degradation tests. It was found that colorless and transparent hydrogels were quickly generated in situ. The gelation time, swelling and degradation behaviors of this kind of hydrogels could be adjusted by changing the concentration of the macromer solution in PBS buffer (pH 7.4). This novel hydrogel is expected to be used as a biomedical material.     

Preparation and properties of redox responsive modified hyaluronic acid hydrogels for drug release

A series of oxidized hyaluronic acid (oxi‐HA)/3,3′‐dithiobis (propionohydrazide) (DTP) redox responsive hydrogels by Schiff base reaction under physiological conditions were designed and prepared. The influence of the concentration of oxi‐HA and DTP on rheological properties, equilibrium swelling ratio, and degradation rate were investigated. All oxi‐HA/DTP hydrogels exhibited good rheological properties, high equilibrium swelling ratio, low degradation rate, and sustainable drug release properties, and the comprehensive performance of oxi‐HA5/DTP6 hydrogel was better than that of others. The redox responsiveness was evaluated by means of degradation and in vitro bovine serum albumin release behavior investigation with the stimulus of different concentration of dithiothreitol as reducing agent. The intelligent hydrogels could be potentially applied in the fields of drug delivery system, tissue engineering, or cell scaffold materials. Copyright © 2017 John Wiley & Sons, Ltd.     

Synthesis and characterization of novel thermoresponsive‐co‐biodegradable hydrogels composed of N‐isopropylacrylamide,poly(L‐lactic acid), and dextran

A series of novel multifunctional hydrogels that combined the merits of both thermoresponsive and biodegradable polymeric materials were designed, synthesized, and characterized. The hydrogels were copolymeric networks composed of N‐isopropylacrylamide (NIPAAM) as a thermoresponsive component, poly(L‐lactic acid) (PLLA) as a hydrolytically degradable and hydrophobic component, and dextran as an enzymatically degradable and hydrophilic component. The chemical structures of the hydrogels were characterized by an attenuated total reflection–Fourier transform infrared spectroscopy (ATR–FTIR) technique. The hydrogels were thermoresponsive, showing a lower critical solution temperature (LCST) at approximately 32 °C, and their swelling properties strongly depended on temperature changes, the balance of the hydrophilic/hydrophobic components, and the degradation of the PLLA component. The degradation of the hydrogels caused by hydrolytic cleavage of ester bonds in the PLLA component was faster at 25 °C below the LCST than at 37 °C above the LCST, determined by the ATR–FTIR technique. Due to their multifunctional properties, the designed hydrogels show great potential for biomedical applications, including drug delivery and tissue engineering. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5054–5066, 2004