有机-无机纳米复合水凝胶*

本文综述了近年来有机-无机纳米复合水凝胶领域的研究进展。针对无机成分的不同种类及复合形式,本文将目前已见报道的有机-无机纳米复合水凝胶划分为三类,分别为层状硅酸盐纳米插层复合水凝胶、粘土交联纳米复合水凝胶和二氧化硅纳米杂化复合水凝胶。阐述了三类纳米复合水凝胶的发展趋势,特别就它们的合成方法进行了详细归纳与总结。在此基础上,介绍了纳米无机成分对复合水凝胶的性能增强机理,并就三者之间的增强差异进行了说明。     

明胶凝胶表面润湿性的研究

本工作利用测定几种参照液体在明胶凝胶上的接触角,定量地估算了明胶凝胶的表面自由能。加入表面活性剂,尤其是非离子表面活性剂,能增加明胶凝胶的表面自由能(主要是其极性分量)并大大改善明胶凝胶的表面润湿性。在表面上分子的吸附与定向和明胶凝胶中非极性网状结构形成的基础上,解释了上述实验结果。     

P(AMPS-co-BMA)水凝胶的电场敏感性及电刺激响应机理

以离子型单体2-丙烯酰胺-2-甲基丙磺酸(AMPS)及非离子型单体甲基丙烯酸丁酯为原料, 偶氮二异丁腈为引发剂, N,N′-亚甲基双丙烯酰胺为交联剂, N,N-二甲基甲酰胺为溶剂, 通过自由基聚合合成了一系列聚离子浓度不同的聚(2-丙烯酰胺-2-甲基丙磺酸-co-甲基丙烯酸丁酯)电场敏感性水凝胶. 研究了其在去离子水及NaCl溶液中的溶胀行为. 结果表明, 该水凝胶在去离子水中的平衡溶胀度在236.4~298.5之间, 其溶胀速率随着AMPS用量的增加而增加; 并且随着凝胶内部聚离子浓度的增加, 凝胶在NaCl溶液中的消溶胀速率及消溶胀度逐渐减小. 凝胶的电刺激响应性能研究结果表明, 在电场存在下, 凝胶在NaCl溶液中的溶胀行为与凝胶内部聚离子浓度和溶液中NaCl浓度的相对大小有关, 当凝胶内部聚离子浓度大于溶液中NaCl浓度时, 凝胶溶胀, 反之则凝胶消溶胀; 而且, 凝胶在电场作用下的偏转行为同样与凝胶内部聚离子浓度和溶液中NaCl浓度的相对大小有关, 当凝胶内部聚离子浓度大于溶液中NaCl浓度时, 偏向阴极, 反之则凝胶偏向阳极. 另外, 在电场存在下, 凝胶在NaCl溶液中的电偏转速度与环境温度密切相关.     

Properties of 2-hydroxy-ethylmethacrylate copolymers and hydrogels based on them

Data on properties of 2-hydroxy-ethylmethacrylate copolymers and hydrogels obtained on their basis are generalized. The effect of conditions of preparation of the hydrogels on their swelling degree in water is analyzed. Peculiarities of swelling of the hydrogels in aqueous solutions of inorganic salts are studied. Properties of hydrogels modified by silicon rubber are presented.     

快速响应温敏水凝胶研究进展

温敏水凝胶是一类具有广泛应用前景的高分子材料,但是由于传统方法合成的水凝胶响应速率较慢因而限制了其应用,因此近年来围绕提高传统水凝胶的响应速率做了大量研究工作。本文从几个方面综述了近年来快速响应的温敏水凝胶的研究进展,并对有关现象进行了解释和说明。     

烷氧磺酸盐功能化的聚乙撑二氧噻吩水凝胶

通过氧化偶联聚合方法成功地制备出一种基于烷氧磺酸盐功能化的聚乙撑二氧噻吩水凝胶, 揭示了零维单体胶束向二维纳米片层及三维水凝胶的转变过程, 发现通过改变反应温度或初始单体浓度, 可以诱导水凝胶网络结构单元的维度变化, 即由零维纳米粒子向二维纳米片层进行转化. 提出了一种导电高分子水凝胶的合成方法, 即采用一种氧化剂与一种多价金属盐的混合物作为引发剂, 其中前者用于诱导单体聚合, 后者则充当离子交联试剂, 并发现可以通过引入不同金属离子来改变凝胶的形貌. 此外, 导电高分子水凝胶具有良好的电化学电容, 并具有选择性吸附与可控脱附某些染料分子的特性.     

Preparation of Injectable Composite Hydrogels by Blending Poloxamers with Calcium Carbonate-Crosslinked Sodium Alginate

The effects of calcium carbonate-crosslinked sodium alginate on poloxamer hydrogels have been investigated. The mechanical strength, degradability, and thermal stability of hydrogels were characterized. The chemical and physical crosslinking in the composite hydrogels has resulted in an improvement of the compressive strength and elasticity of the hydrogels. These mixed hydrogels showed improved mechanical properties, elasticity, and stability as well as environmental responsiveness and injectability.     

Synthesis of Anisotropic Hydrogels and Their Applications

Owing to their water‐rich structures, which are similar to those of biological tissues, hydrogels have long been regarded as promising scaffolds for artificial tissues and organs. However, in terms of the structural anisotropy, most synthetic hydrogels are substantially different from biological systems. Synthetic hydrogels are usually composed of randomly oriented three‐dimensional polymer networks whereas biological systems adopt anisotropic structures with hierarchically integrated building units. Such anisotropic structures often play essential roles in biological systems to exhibit particular functions. In this context, anisotropic hydrogels provide an entry point for exploring biomimetic applications of hydrogels. Reflecting these aspects, an increasing number of studies on anisotropic hydrogels have been reported recently. This Minireview highlights the use and perspectives of these anisotropic hydrogels, particularly focusing on their preparation, structures, and applications.     

智能型水凝胶结构及响应机理的研究进展

综述了智能型水凝胶研究的新进展,简要介绍了几类新型的刺激响应性水凝胶,分析了影响水凝胶敏感性的结构因素,介绍了水凝胶的有关理论,动力学研究和敏感性机理。     

Nanocomposite hydrogels based on carbon dots and polymers

Nanocomposite hydrogels based on carbon dots(CDs) and polymers have emerged as new materials with integrated properties of individual components,leading to their important applications in the field of soft nanomaterials.This perspective highlights recent advances in the development of nanocomposite hydrogels from CDs and polymers.We review the preparation methods of nanocomposite hydrogels based on CDs and polymers,and emerging applications of these nanocomposite hydrogels such as environmental remediation,energy storage,sensing,drug delivery and bioimaging.We conclude with the discussion of new research directions in the development of new type of nanocomposite hydrogels based on CDs and polymers.     

Recent developments of polysaccharide-based double-network hydrogels

Polysaccharides possessing distinctive properties, such as biocompatibility, biodegradability, and nontoxicity, are promising matrices for hydrogels. However, the polysaccharides-based hydrogels have poor mechanical properties, which is a major limitation for their applications. In recent years, researches on double-network (DN) hydrogels with outstanding mechanical properties have gained increasing attention. Therefore, the main research orientation is to combine the benefits of both materials and broaden their applications in various fields. This paper reviews the recent progress of polysaccharide-based DN (PDN) hydrogels that show great advantages in mechanical, physiochemical properties, biocompatibility, biodegradability and so on. The preparation, structure, and unique properties of different PDN hydrogels are discussed in detail. Moreover, we summarize the applications of PDN hydrogels in biomedical and energy storage and conversion fields. This research progress is breaking through the limitations of PDN hydrogels and opening a new avenue for their future development.     

A review on tough and sticky hydrogels

In this review, we survey recent literature (2009–2013) on hydrogels that are mechanically tough and adhesive. The impact of published work and trends in the field are examined. We focus on design concepts, new materials, structures related to mechanical performance and adhesion properties. Besides hydrogels made of individual polymers, concepts developed to toughen hydrogels include interpenetrating and double networks, slide ring polymer gels, topological hydrogels, ionically cross-linked copolymer gels, nanocomposite polymer hydrogels, self-assembled microcomposite hydrogels, and combinations thereof. Hydrogels that are adhesive in addition to tough are also discussed. Adhesive properties, especially wet adhesion of hydrogels, are rare but needed for a variety of general technologies. Some of the most promising industrial applications are found in the areas of sensor and actuator technology, microfluidics, drug delivery and biomedical devices. The most recent accomplishments and creative approaches to making tough and sticky hydrogels are highlighted. This review concludes with perspectives for future directions, challenges and opportunities in a continuously changing world.     

Preparation and Characterization of Attractive Poly(amino acid)Hydrogels Based on 2-Ureido-4[1H]-pyrimidinone

Self-healing hydrogels with the shear-thinning property are novel injectable materials and are superior to traditional injectable hydrogels.The self-healing hydrogels based on 2-ureido-4[1 H]-pyrimidinone(UPy)have recently received extensive attention due to their dynamic reversibility of UPy dimerization.However,generally,UPy-based self-healing hydrogels exhibit poor stability,cannot degrade in vivo and can hardly be excreted from the body,which considerably limit their bio-application.Here,using poly(l-glutamic acid)(PLGA)as biodegradable matrix,branchingα-hydroxy-ω-amino poly(ethylene oxide)(HAPEO)as bridging molecule to introduce UPy,and ethyl acrylate polyethylene glycol(MAPEG)to introduce double bond,the hydrogel precursors(PMHU)are prepared.A library of the self-healing hydrogels has been achieved with well self-healable and shear-thinning properties.With the increase of MAPEG grafting ratio,the storage modulus of the self-healing hydrogels decreases.The self-healing hydrogels are stable in solution only for 6 h,hard to meet the requirements of tissue regeneration.Consequently,ultraviolet(UV)photo-crosslinking is involved to obtain the dual crosslinking hydrogels with enhanced mechanical properties and stability.When MAPEG grafting ratio is 35.5%,the dual crosslinking hydrogels can maintain the shape in phosphate-buffered saline solution(PBS)for at least 8 days.Loading with adipose-derived stem cell spheroids,the self-healing hydrogels are injected and self-heal to a whole,and then they are crosslinked in situ via UV-irradiation,obtaining the dual crosslinking hydrogels/cell spheroids complex with cell viability of 86.7%±6.0%,which demonstrates excellent injectability,subcutaneous gelatinization,and biocompatibility of hydrogels as cell carriers.The novel PMHU hydrogels crosslinked by quadruple hydrogen bonding and then dual photo-crosslinking of double bond are expected to be applied for minimal invasive surgery or therapies in tissue engineering.     

Structural design of stimuli‐responsive bioconjugated hydrogels that respond to a target antigen

Stimuli‐responsive bioconjugated hydrogels that can respond to a target antigen (antigen‐responsive hydrogels) were prepared by introducing antigen‐antibody bindings as reversible crosslinks into the gel networks. The preparation conditions of the antigen‐responsive hydrogels and the mechanism of the antigen‐responsive behavior were investigated, focusing on bioconjugated hydrogel structures. This article also focuses on the effect of semi‐interpenetrating polymer network (semi‐IPN) structures on the antigen‐responsive swelling/shrinking behavior of bioconjugated hydrogels with antigen‐antibody bindings. The preparation conditions and the network structures of the bioconjugated hydrogels are discussed in relation to designing antigen‐responsive hydrogels. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 2144–2157, 2009     

Birefringent hydrogels based on PAAm and lyotropic liquid crystal: Optical, morphological and hydrophilic characterization

In this work, hydrogels of polyacrylamide (or PAAm) with confined lyotropic liquid crystal (potassium laurate-decanol-water, KL-DeOH-H₂O) (or LLC) were synthesized. The hydrogels were characterized by polarized optical microscopy (POM), refractometry, optical transmission, scanning electron microscopy (SEM) and small angle X-ray scattering (SAXS). Besides these techniques, the hydrophilicity of hydrogels was characterized by the degree of swelling. Based on POM, it was observed that the texture of the birefringent hydrogels obtained depends on their cross-linking density, and that it is formed soon after hydrogel synthesis. Refractometry results indicated an behavior antagonist to that obtained for the system constituted by thermotropic liquid crystal inserted into the PAAm lattice in relation to the dependence of Δn on the AAm concentration and the optical transmittance. SEM micrographs show that birefringent hydrogels present rougher surface when compared to the surface of PAAm hydrogels. For the same AAm concentrations, it was observed that the hydrogels with confined LLC present larger swelling values (Q) when compared to those of PAAm hydrogels. The loss of water by birefringent hydrogels is twofold slower than that of PAAm hydrogels. Hydrogels formed by PAAm and lyotropic liquid crystal synthesized in this work can be potentially used in optical devices.     

Design and fabrication of functional hydrogels through interfacial engineering

Hydrogels have drawn considerable attention in the past two decades due to their excellent biocompatibility and multi-stimuli responsiveness. They have a wide range of applications in the fields related to tissue engineering, sensors and biomedicine. Their applications are strongly influenced by the surface properties of hydrogels and the interfacial interactions between hydrogels and other substrates. In particular, the surface wettability and adhesion of hydrogels decide their applications as drug carriers and wound dressing materials. Nevertheless, there is a lack of systematic discussion on the surface functionalization strategies of hydrogels. Therefore, this review aims at summarizing the strategies of functionalizing the surfaces of hydrogels and bonding hydrogels with other solid substrates. It also explores the challenges and future perspectives of interfacial engineering of hydrogels.     

Biocompatible hydrogels based on chitosan,cellulose/starch,PVA and PEDOT:PSS with high flexibility and high mechanical strength

Fabricating mechanically strong hydrogels that can withstand the conditions in internal tissues is a challenging task. We have designed hydrogels based on multicomponent systems by combining chitosan, starch/cellulose, PVA, and PEDOT:PSS via one-pot synthesis. The starch-based hydrogels were homogeneous, while the cellulose-based hydrogels showed the presence of cellulose micro- and nanofibers. The cellulose-based hydrogels demonstrated a swelling ratio between 121 and 156%, while the starch-based hydrogels showed higher values, from 234 to 280%. Tensile tests indicated that the presence of starch in the hydrogels provided high flexibility (strain at break?>?300%), while combination with cellulose led to the formation of stiffer hydrogels (elastic moduli 3.9–6.6 MPa). The ultimate tensile strength for both types of hydrogels was similar (2.8–3.9 MPa). The adhesion and growth of human osteoblast-like SAOS-2 cells was higher on hydrogels with cellulose than on hydrogels with starch, and was higher on hydrogels with PEDOT:PSS than on hydrogels without this polymer. The metabolic activity of cells cultivated for 3 days in the hydrogel infusions indicated that no acutely toxic compounds were released. This is promising for further possible applications of these hydrogels in tissue engineering or in wound dressings.

Graphical abstract

     

Chitosan-Carboxymethylcellulose Hydrogels as Supports for cell Immobilization

Abstract

The preparation of hydrogels from the polyelectrolyte complexation (PEC) of carboxymethylcellulose (CMC) and hydrogels from the complexation with an additional or simultaneous ionotropic gelation is reported. The reaction yield is high enough and depends strongly on the additional ionotropic gelation (IG). Infrared spectroscopy was used to confirm complexation between the carboxylic (in CMC) and amine (in chitosan) groups. The scanning electron microscope images show the formation of a fibrillar structure with characteristic pore sizes between 0.1 and 1 μm. The swelling capacity, Q, of PEC hydrogels is not high, but the Q value of hydrogels from PEC with an additional IG is high and depends strongly on the pH medium. These hydrogels are mechanically more stable than the PEC hydrogels; their mechanical strength is about 7 times higher than that of PEC hydrogels. The hydrogels were used to immobilize yeast cells with the cell density 1 × 10⁹ cells/mL, about 100 times higher than that in the free-cell culture. Only the hydrogels with additional IG were stable enough for continuous fermentation over 10 days. These hydrogels proved to have higher affinity to substrate, which led to higher productivity than the ionotropic gel of CMC and aluminum ion.     

Preparation and characterization of pH- and temperature-responsive semi-IPN hydrogels of carboxymethyl chitosan with poly (<Emphasis Type="Italic">N</Emphasis>-isopropyl acrylamide) crosslinked by clay

A new kind of pH- and temperature-responsive semi-interpenetrating polymer network hydrogel based on linear carboxymethylchitosan (CMCS) and poly (N-isopropylacrylamide) (PNIPA) crosslinked by inorganic clay was prepared. The pH-and temperature-responsive behaviors, the deswelling kinetics, and the mechanical properties of the hydrogel were investigated. The hydrogels exhibited a volume phase transition temperature around 33 °C with no significant deviation from the conventional PNIPA hydrogels. The results of the influence of pH value on the swelling behaviors showed that the minimum swelling ratios of the hydrogels appeared near the isoelectric point (IEP) of CMCS, and when pH deviated from the IEP, the hydrogels behaved as polycations or polyanions. The novel hydrogels had much higher response rate than the conventional CMCS/PNIPA hydrogels. Moreover, the semi-IPN hydrogels crosslinked by clay could be elongated to more than 800% and the elongation could be recovered almost completely and instantaneously.     

Structure and swelling-release behaviour of poly(vinyl pyrrolidone) (PVP) and acrylic acid (AAc) copolymer hydrogels prepared by gamma irradiation

Copolymer network hydrogels were prepared by gamma irradiation of aqueous solutions of poly(vinyl pyrrolidone) (PVP) and acrylic acid monomer (AAc). The composition of the final hydrogels compared to the composition of the initial preparation solutions of hydrogels was determined. The chemical structure and nature of bonding was characterized by IR spectroscopy analysis, while the thermal durability of the prepared hydrogels was assessed by thermogravimetric analysis (TGA). The kinetic swelling in water and the pH-sensitivity of PVP/AAc copolymer hydrogels was studied. The drug release properties of PVP/AAc hydrogels taking methyl orange indicator as a drug model was investigated. The IR spectra indicate the formation of copolymer networks, whereas the TGA study showed that the PVP/AAc hydrogels possess higher thermal stability than pure PAAc and lower than PVP hydrogels. The kinetic swelling in water showed that all the hydrogels reached equilibrium after 24 h and that the degree of swelling increases with increasing the ratio of AAc in the initial feeding solutions. It was found that the degree of swelling of PVP/AAc hydrogels increases greatly within the pH range 4-7 depending on composition.