Preparation of CaCO3‐based biomineralized polyvinylpyrrolidone–carboxymethylcellulose hydrogels and their viscoelastic behavior

In the blend of natural and synthetic polymer‐based biomaterial of polyvinylpyrrolidone (PVP) and carboxymethylcellulose (CMC), fabrication of CaCO₃ was successfully accomplished using simple liquid diffusion technique. The present study emphasizes the biomimetic mineralization in PVP–CMC hydrogel, and furthermore, several properties of this regenerated and functionalized hydrogel membranes were investigated. The physical properties were studied and confirmed the presence of CaCO₃ mineral in hydrogel by Fourier transform infrared spectroscopy and Scanning electron microscopy. Moreover, the absorptivity of water and mineral by PVP–CMC hydrogel was studied to determine its absorption capacity. Further, the viscoelastic properties (storage modulus, loss modulus, and complex viscosity) of mineralized and swelled samples (time: 5–150 min) were measured against angular frequency. It is interesting to know the increase of elastic nature of mineralized hydrogel filled with CaCO₃ maintaining the correlation between elastic property and viscous one of pure hydrogel. All these properties of biomineralized hydrogel suggest its application in biomedical field, like bone treatment, bone tissue regeneration, dental plaque and tissue replacement, etc. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40237.     

水凝胶的制备

主要叙述了水凝胶的各种制备方法,包括化学方法和物理方法,不同的高分子原料和不同的制备方法所得到的水凝胶的性质会有所差异,可以满足不同领域的应用需求。     

离子凝胶复合吸附剂的制备及空气取水性能

制备了一种LiCl复合可得然离子凝胶,并将其首次用于空气取水性能研究。在不同吸附温度、吸附湿度的开式环境中,完成了复合吸附剂的水蒸气吸附特性研究。探究了浸渍盐的质量浓度对复合吸附剂吸附性能的影响。根据目标工况,完成了复合吸附剂组分的优化配比。对优化后的离子凝胶进行了吸附动力学和等温吸附特性研究。结果表明,15% LiCl溶液复合而成的可得然吸附剂综合性能最佳。在35℃&75%RH下,该复合吸附剂的吸附量高达3.30g/g,是传统硅胶复合吸附剂的6.6倍;在55℃&40%RH工况下实现1.66 g/g的水量脱附,是硅胶复合吸附剂的3倍。在25℃&75%RH下,可得然复合凝胶吸附剂的吸附速率K高达3.48×10^-3s^-1;该离子凝胶复合吸附剂的研究,为吸附式空气取水技术提供了基础支持。     

双重动态共价键交联纳米纤维素导电水凝胶及其柔性传感器

自愈合导电水凝胶因其良好的自愈合性能与导电性能,在柔性可穿戴设备中具有巨大的应用前景。以4-甲酰基苯硼酸（Bn）交联聚乙烯醇（PVA）和聚乙烯亚胺（PEI）构建基于硼酸酯键和亚胺键的双重动态交联水凝胶网络,引入聚吡咯修饰的纤维素纳米纤维（PPy@CNF）构建了具有良好自愈合和导电性的PBP-PPy@CNF纳米复合水凝胶。结果表明,当PPy@CNF的质量分数为0.8%时,水凝胶的力学性能最佳,其最大应力可达6.65kPa,断裂拉伸应变可达2080%,电导率为2174μS/m。基于该水凝胶的电阻式传感器具有良好的稳定性和重复性,在应变检测范围0~800%内,灵敏因子GF可分为三个线性响应区域,分别是0~200%（GF₁=2.82）、200%~600%（GF₂=7.15）和600%~800%（GF₃=12.85）,该传感器能有效检测人体不同部位的运动,可应用于可穿戴传感设备。     

基于荧光水凝胶的功能表面器件

基于水凝胶体系的功能材料及应用发展迅速,在包括组织工程、能源存储、柔性器件等领域展现出广阔的应用前景。采用聚乙烯醇、壳聚糖和琼脂糖构建水凝胶主体结构,并添加羟乙基纤维素增塑保湿,添加碳量子点赋予材料荧光效应。制备获得了兼具有优良的自修复性能和优异拉伸性能的多网络结构水凝胶,具有高达33 MPa的拉伸强度并能够在多种媒介环境下实现快速的自修复,在空气中60 s自修复效率达93%。研究发现复合水凝胶材料的荧光强度同表面所受压强呈负相关性,而同其拉伸伸长率呈正相关。数据拟合证实,通过检测水凝胶的荧光强度可以监控其变形率,而结合水凝胶和仿壁虎表面结构制备出能够黏附于多种表面的压强检测器,通过对器件荧光强度的检测能够探测液下环境压强。该研究拓展了荧光水凝胶材料的应用途径,有望用于液下压强探测、工程结构失效监控等。     

快速响应型P(NIPA-co-SA)水凝胶制备及温敏性能

研究具有较高LCST且响应速率快的温敏性水凝胶。以NaCl水溶液为反应介质,采用相分离法合成了多孔水凝胶P(NIPA-co-SA)。利用傅立叶变换红外光谱仪(FT-IR)表征产物结构,并借助扫描电子显微镜、差示扫描量热法(DSC)、浊度法等手段研究了反应介质浓度对产物微观形貌、相变温度和相变响应速率的影响规律。结果表明,P(NIPA-co-SA)水凝胶具有对温度敏感的响应特性,其低临界溶解温度(LCST)可达到75℃。NaCl水溶液浓度不影响产物的LCST,且随着反应中NaCl水溶液浓度的提高,水凝胶表面逐渐出现不连续的浅而封闭的小孔到互相贯穿的开孔,水凝胶相变响应速率在一定范围内逐渐提高,具有快速响应特性。     

Hydrogel‐mediated formation of living cartilage template for endochondral initiation

The use of hydrogel in cartilage tissue engineering is especially popular due to its high hydrophilic property which is similar to native cartilage matrix. Alginate hydrogel was used as a transient scaffold material to facilitate chondrocyte proliferation into a three‐dimensional scaffold‐free living hyaline cartilaginous graft (LhCG). As LhCG is purely cell‐based and has a marked resemblance to native hyaline cartilage, it served as an excellent in vitro platform for studying the endochondral ossification pathway. Due to the complexity of events involved throughout endochondral ossification, this study only focuses on early stages of the process where it involves chondrocyte hypertrophy and blood vessel invasion. Human umbilical vein endothelial cells (HUVECs) were selected as the target cells for possible endothelialization in the LhCG template. They were seeded onto the LhCG construct and subjected to vascular endothelial growth factor (VEGF) treatment. Results suggested that VEGF is indeed a potent driving force for initiation of the endochondral pathway. It alone is sufficient to induce hypertrophy in chondrocytes and the corresponding expression of osteogenic genes with or without the presence of HUVECs in the LhCG template. On the other hand, the effect of HUVECs in the LhCG system was less evident. It is hypothesized that this is attributed to the preservation of anti‐angiogenic properties in primary chondrocytes from the LhCG construct, inhibiting HUVECs from endothelialization in the LhCG+HUVEC construct. Based on the outcome from this study, it is recommended that hypertrophy in chondrocytes should be induced prior to endothelial cell introduction so that the microenvironment will be altered to favor angiogenesis within the cartilaginous template. © 2013 Society of Chemical Industry     

In situ-forming injectable hydrogels for regenerative medicine

Regenerative medicine involves interdisciplinary biomimetic approaches for cell therapy and tissue regeneration, employing the triad of cells, signals, and/or scaffolds. Remarkably, the field of therapeutic cells has evolved from the use of embryonic and adult stem cells to the use of induced pluripotent stem cells. For application of these cells in regenerative medicine, cell fate needs to be carefully controlled via external signals, such as the physical properties of an artificial extracellular matrix (ECM) and biologically active molecules in the form of small molecules, peptides, and proteins. It is therefore crucial to develop biomimetic scaffolds, reflecting the nanoenvironment of three-dimensional (3D) ECM in the body. Here, we describe in situ-forming injectable hydrogel systems, prepared using a variety of chemical crosslinkers and/or physical interactions, for application in regenerative medicine. Selective and fast chemical reactions under physiological conditions are prerequisites for in situ formation of injectable hydrogels. These hydrogels are attractive for regenerative medicine because of their ease of administration, facile encapsulation of cells and biomolecules without severe toxic effects, minimally invasive treatment, and possibly enhanced patient compliance. Recently, the Michael addition reaction between thiol and vinyl groups, the click reaction between bis(yne) molecules and multiarm azides, and the Schiff base reaction have been investigated for generation of injectable hydrogels, due to the high selectivity and biocompatibility of these reactions. Noncovalent physical interactions have also been proposed as crosslinking mechanisms for in situ forming injectable hydrogels. Hydrophobic interactions, ionic interactions, stereocomplex formation, complementary pair formation, and host–guest interactions drive the formation of 3D polymeric networks. In particular, supramolecular hydrogels have been developed using the host–guest chemistry of cyclodextrin (CD) and cucurbituril (CB), which allows highly selective, simple, and biocompatible crosslinking. Molecular recognition and complex formation of supramolecules, without the need for additional additives, have been successfully applied to the 3D network formation of polymer chains. Finally, we review the current state of the art of injectable hydrogel systems for application in regenerative medicine, including cell therapy and tissue regeneration.     

硅水凝胶隐形眼镜材料的合成与性能研究

以甲基丙烯酸羟乙酯（HEMA）、N-乙烯基毗咯烷酮（NVP）和γ-（甲基丙烯酰氧）丙基三甲氧基硅烷（KH-570）为单体,以偶氮二异丁腈（AIBN）为引发剂,通过本体聚合反应合成新型硅水凝胶角膜接触镜.考察了各单体配比、反应温度等对聚合的影响.结果表明,当反应温度为90℃,反应时间为2h,V（HEMA）：V（NVP）：V（KH-570） =8∶ 1∶1时,合成的隐形眼镜透氧量（DK/t）达到64.0×10-9（cm3O2·cm）/（cm2·s·mmHg）,含水量38％,透光率95.5％以上.     

Highly stretchable,ionic conductive and self-recoverable zwitterionic polyelectrolyte-based hydrogels by introducing multiple supramolecular sacrificial bonds in double network

Zwitterionic hydrogels have been explored for applications in electrochemical devices very recently due to their high water retention ability and interesting electrochemical properties. The use of zwitterionic hydrogels in devices requires them tough and recoverable or healable from fatigue damage. Herein, a double network zwitterionic hydrogel contains a reversible noncovalent interaction crosslinked polyvinyl alcohol (PVA) first network, together with a covalent/noncovalent hybrid crosslinked acrylamide and sulfobetaine methacrylate copolymer (P(AM-co-SBMA)) second network, was fabricated by a simple two-steps methods of copolymerization and freezing/thawing. The reversible hydrogen bonds, crystalline domain, and electrostatic interactions in the double networks work as sacrificial bonds to dissipate energy and toughen the materials when hydrogel deforms. The broken bonds can reform upon unloading endowing the recovery of hydrogels' properties with the assistance of the elastic covalent network. The optimal hydrogels are highly stretchable (fracture strain 970%), tough (fracture toughness 693 kJ m⁻³), rapidly recoverable (65% toughness recovery and 75% stiffness recovery after resting 5 min at room temperature) and with widely tunable mechanical properties by multibond crosslinking. Meanwhile, the zwitterionic counterions of SBMA moieties endow the tough and recoverable hydrogels extremely high intrinsic ionic conductivities (7.49 S m⁻¹) at room temperature. This work not only provides a simple strategy for fabricating tough and recoverable zwitterionic hydrogels but also demonstrates multifunctional properties of the zwitterionic hydrogels, which possess a great potential to fulfill flexible devices applications. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47783.