The role of bulky polysiloxanylalkyl methacrylates in polyurethane–polysiloxane hydrogels

Silicone hydrogels based on polyurethane–polysiloxane prepolymer and hydrophilic monomers such as N,N-dimethylacrylamide, although possessing high oxygen permeability and satisfactory tear strength, are too stiff to be targeted for applications such as contact lenses. However, with the inclusion of bulky polysiloxanylalkyl methacrylates, such as methacryloxypropyl tris(trimethylsiloxy)silane (TRIS), to replace part of the polyurethane prepolymer, the hydrogels obtained not only maintained high oxygen permeability, but also had a lower modulus and improved tear strength. These changes in properties are all favorable for applications such as oxygen-permeable hydrogel lenses. © 1996 John Wiley & Sons, Inc.     

Synthetic hydrogels: Synthesis,novel trends,and applications

Hydrogels have been generated and explored for use in various applications. The main objective of this comprehensive review is to collate the fundamental concepts of hydrogels, and elaborate on knowledge gaps, and to provide a perspective on the future directions. This review includes details of constituent molecules (monomers, cross-linkers, composite materials, etc.) and the methods used to prepare polymer networks. Moreover, the review highlights modifications of hydrogels that introduce new properties or enhance the existing features to suit the desired applications and challenges of synthetic polymer hydrogels. The other important topics covered in this review are the synthesis and applications of 3D printed hydrogels, nanocomposite hydrogels, injectable hydrogels, and self-healing hydrogels.     

环境刺激响应型高强度智能水凝胶研究进展

环境刺激响应型智能水凝胶能够对外界环境因素的变化产生显著的体积或其他特性的变化,且其性质和结构与生物组织类似,有望应用于人工软骨、人造肌肉、组织工程等领域,引起了广泛的关注。提高环境刺激响应型智能水凝胶的力学性能是智能水凝胶应用研究的重要方向之一。本文综述了近年来环境刺激响应型高强度智能水凝胶的研究进展,简述了高强度智能水凝胶的网络结构的构建策略与方法,分析了其具备高力学性能的机理,重点介绍了4类不同结构的高强度智能水凝胶,即超低交联结构水凝胶、纳米颗粒复合水凝胶、拓扑结构水凝胶以及双网络结构水凝胶,最后讨论了环境刺激响应型高强度智能水凝胶在面向应用的研究过程中仍然需要解决的关键科学问题,如智能水凝胶的环境刺激与力学性能的博弈效应以及响应环境刺激前后的力学性能差异等。     

The synthesis,mechanisms, and additives for bio-compatible polyvinyl alcohol hydrogels: A review on current advances,trends, and future outlook

Vinyl polymers are widely used in biological, textile and industrial applications and are currently attracting research attention for specialized bio-based applications. Polyvinyl alcohol (PVA) hydrogels show great advantages as a material with high biocompatibility, permeability, hydrophilicity, and low-friction coefficient, allowing applications as smart materials, wound dressings, and flexible sensors. However, the poor mechanical properties of PVA hydrogels and biocompatibility less than natural polymers make them unsuitable in practical applications. Additives are often added to PVA hydrogels to enhance mechanical properties, endow more compatibility, functionality and expand their application range. Among them, bio-additives such as nanocellulose, natural polysaccharides and proteins are biodegradable, biocompatible, and inexpensive, broadening their applications in the biomedical and tissue engineering fields. This work reviews the synthesis of PVA hydrogels, methods to enhance their mechanical properties, types of bio-additives incorporated for biocompatibility, their mechanism of interaction with PVA and future prospects of PVA composite bio-hydrogels for application in various fields. Representative cases are carefully selected and discussed with regard to their composition and pros and cons are discussed. Finally, future requirements, as well as the opportunities and challenges of these bio-additives for improving the multifunctionality of PVA hydrogels are also presented.     

Theophylline-loaded pectin-based hydrogels. II. Effect of concentration of initial pectin solution,crosslinker type and cation concentration of external solution on drug release profile

A series of drug-loaded pectin hydrogels were prepared by mixing method in two ion types, Ca⁺² or Zn⁺², for wound dressing applications and their drug release performances were investigated at pH 6.4 in four different calcium ion concentrations of external solution. Pectin hydrogels were synthesized in three different concentrations of initial pectin solution and theophylline was used as a model drug. Fourier transform infrared spectroscopy, scanning electron microscopy, and atomic force microscopy were used for hydrogel characterization. Additionally, fluid handling capacity, swelling behavior, dehydration rate, dispersion characteristic, dressing pH determination, water vapor permeability, oxygen permeability, surface contact angle, flexibility, mass per unit area, and thickness were determined for selected hydrogels. One of the most valuable contributions of our study is that the concentration of initial pectin solution and calcium ion concentration of external solution are very important parameters to obtain an effective drug release. After evaluating all data, we have shown that flexible and transparent pectin-based wound dressings can be synthesized as a controlled drug release system. Zinc-containing hydrogel was antibacterial against Staphylococcus aureus and Escherichia coli but not suitable for cell migration. On the other hand, calcium-based hydrogel was nontoxic on the fibroblast cells and it had no negative effect on cell migration. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48155.     

互穿网络聚合物水凝胶的制备及其吸附研究进展

互穿网络聚合物(IPN)水凝胶在分离技术领域具有广泛的应用前景,这些年受到人们广泛关注.本文介绍了聚多糖基(壳聚糖、海藻酸、淀粉和其他聚多糖)、蛋白质基(明胶、胶原蛋白、丝纤蛋白和大豆蛋白)和合成聚合物基(非离子型和离子型)IPN水凝胶的制备方法,主要包括同步-IPN、分步-IPN和半-IPN的制备方法.为了提高聚合物水凝胶的生物相容性、溶胀率和机械强度,采用天然高分子与合成高分子共混制备IPN水凝胶.与单网络水凝胶相比,IPN水凝胶对染料和重金属离子的吸附速率快、吸附容量大.为了达到选择性吸附和提高水凝胶的比表面积,制备离子印迹IPN水凝胶和多孔IPN复合冷冻凝胶,是未来研究高效吸附IPN水凝胶的发展方向之一.     

Hydrogels as smart biomaterials

Hydrogels were the first biomaterials rationally designed for human use. Beginning with the pioneering work of Wichterle and Lím on three‐dimensional polymers that swell in water, we review the design, synthesis, properties, and applications of hydrogels. The field of hydrogels has moved forward at a dramatic pace. The development of suitable synthetic methods encompassing traditional chemistry to molecular biology has been used in the design of hydrogels mimicking basic processes of living systems. Stimuli‐sensitive hydrogels, hydrogels with controlled degradability, genetically engineered poly(amino acid) polymers reversibly self‐assembling in precisely defined three‐dimensional structures, and hybrid polymers composed of two distinct classes of molecules are just some examples of these exciting novel biomaterials. The biocompatibility of hydrogels and their applications from implants to nanomaterials are also reviewed. Copyright © 2007 Society of Chemical Industry     

导电水凝胶的制备及应用研究进展

导电水凝胶是一类将亲水性基质和导电介质有机结合的新型水凝胶,具有较高的柔韧性、可调的力学性能和优异的电化学性能,在柔性电子设备等领域具有广阔的应用前景。本文综述了导电水凝胶材料的研究前沿和动态,介绍了导电水凝胶的分类及制备方法,讨论了导电水凝胶的结构设计与性能,重点阐述了导电水凝胶材料的应用研究进展,归纳了导电水凝胶材料面临的问题与挑战,并展望了导电水凝胶材料的发展趋势,指出采用天然可再生资源为原料开发具有高导电性、力学性能稳定、耐极端温度、生物相容性和生物可降解的导电水凝胶将成为下一步研究重点,同时优化柔性电子装置、提高器件输出稳定性也将成为重要的研究方向之一。导电水凝胶的制备及应用研究将促进柔性电子功能材料领域的快速发展。     

Hydrogele: Verwendungsmöglichkeiten und thermodynamische Eigenschaften

Hydrogels are crosslinked macromolecules in which at least part of the network consists of hydrophilic groups. Hydrogels are widespread in nature; for example, plant and animal tissues consist mainly of hydrogels. They are becoming increasingly important in chemical engineering, e. g. as ion excahngers, in gel chromatography, and for dewatering. Hydrogels swell or shrink in aqueous solutions. Such swelling equilibria are the basis for most of their applications. This article surveys the applications and also the swelling behaviour of hydrogels. It covers both the termodynamic principles and methods for correlation of experimentally determined swelling equilibria for nonionic and ionic hydrogels. The swelling of a hydrogel results from the interplay of intermolecular interactions in aqueous, partly ionic polymer solutions on the one hand and elastic properties of polymeric networks on the other. It ist therefore hardly surprising that it is presently impossible to quantitatively predict phase equilibria and the swelling behaviour of such hydrogels from a few basic data. However, it is possible to describe the swelling of hydrogels with straightforward approaches reported in the literature if a number of the parameters of these approaches are adapted to experimentally determined swelling data.     

Enzyme-Responsive Hydrogels as Potential Drug Delivery Systems—State of Knowledge and Future Prospects

Fast advances in polymer science have provided new hydrogels for applications in drug delivery. Among modern drug formulations, polymeric type stimuli-responsive hydrogels (SRHs), also called smart hydrogels, deserve special attention as they revealed to be a promising tool useful for a variety of pharmaceutical and biomedical applications. In fact, the basic feature of these systems is the ability to change their mechanical properties, swelling ability, hydrophilicity, or bioactive molecules permeability, which are influenced by various stimuli, particularly enzymes. Indeed, among a great number of SHRs, enzyme-responsive hydrogels (ERHs) gain much interest as they possess several potential biomedical applications (e.g., in controlled release, drug delivery, etc.). Such a new type of SHRs directly respond to many different enzymes even under mild conditions. Therefore, they show either reversible or irreversible enzyme-induced changes both in chemical and physical properties. This article reviews the state-of-the art in ERHs designed for controlled drug delivery systems (DDSs). Principal enzymes used for biomedical hydrogel preparation were presented and different ERHs were further characterized focusing mainly on glucose oxidase-, β-galactosidase- and metalloproteinases-based catalyzed reactions. Additionally, strategies employed to produce ERHs were described. The current state of knowledge and the discussion were made on successful applications and prospects for further development of effective methods used to obtain ERH as DDSs.     

具有快速响应特性的环境响应型智能水凝胶的研究进展

环境响应智能水凝胶应用于化学传感器、化学微阀、人造肌肉、药物控释载体、物质分离等领域时常常需要快速响应特性,提高智能水凝胶的响应速率成为了智能水凝胶研究领域的重要课题之一。本文主要综述了具有快速响应特性的环境响应智能水凝胶的构建策略与方法,重点介绍了3类具有不同结构的快速响应型智能水凝胶,即具有多孔结构的快速响应智能水凝胶、具有梳状结构的快速响应智能水凝胶以及具有微球复合结构的快速响应智能水凝胶。     

基于重组蛋白质的水凝胶

基于重组蛋白质的水凝胶在生物医学领域有广泛的潜在应用,因此这一领域在近20年吸引了研究工作者的极大研究热情并取得了巨大的进展。在这篇综述中,我们简要地讨论了基于重组蛋白质的水凝胶领域的最新进展,所涵盖的内容包括以生物识别为驱动力的物理交联的水凝胶以及化学交联的水凝胶的设计和构筑,以及它们在生物医学领域的应用。同时我们也讨论这一进展迅速的生物材料领域的发展前景与方向。     

Chitosan‐based hydrogels: recent design concepts to tailor properties and functions

Chitosan (CS) has received much attention as a functional biopolymer for designing various hydrogels for biomedical applications. This review provides an overview of the different types of CS‐based hydrogels, the approaches that can be used to fabricate hydrogel matrices with specific features and their applications in controlled drug delivery and tissue engineering. Emphasis is laid on the recent design concepts of hybrid hydrogels based on mixtures of CS and natural or synthetic polymers, interpenetrating polymer networks as well as composite hydrogels prepared by embedding nanoparticles into CS matrices. © 2017 Society of Chemical Industry     

A Carbodiimide Cross-Linked Silk Fibroin/Sodium Alginate Composite Hydrogel with Tunable Properties for Sustained Drug Delivery

Carbodiimide cross-linked silk fibroin (SF)/sodium alginate (SA) composite hydrogels with superior stability and tunable properties are developed by varying preparation parameters. SF/SA blend ratio modulation allows to achieve composite hydrogel gelation times of 18–65 min, and rheological analysis shows that the speed of gel formation, the hydrogel network's density, and the hydrogels’ compressive properties are closely related to the blend ratio. The G′ of different hydrogels varies substantially from 28 to 413 Pa, and the hydrogel with higher SF content has a greater stiffness. The composite hydrogels present appropriate porosity of 76.63–85.09% and pore size of 316–603 µm. Hydrogel stability improves significantly after cross-linking, and substantial swelling occurs due to the hydrophilicity of SA. The 7/3 and 6/4 SF/SA hydrogels are more resistant to degradation in PBS, and cytotoxicity testing confirmed their biocompatibility. For release studies in vitro, two model compounds are used as drug models, tetracycline hydrochloride, and bovine serum albumin (BSA). Different ratios of SF/SA have a greater influence on the release of BSA. This study provides a practical preparation method for flexible SF/SA composite hydrogels, which can help design hydrogels with specific physicochemical properties for different applications, especially drug delivery.     

Role of bulky polysiloxanylalkyi methacrylates in oxygen-permeable hydrogel materials

Polysiloxanylalkyl methacrylates, such as methacryloxypropyl tris(trimethylsiloxy)silane (TRIS), have been used extensively in rigid gas-permeable contact lens materials due to their ability to produce high oxygen permeability in the resulting polymeric material. In this study, the role of TRIS was evaluated as a component in silicone hydrogel materials based on polysiloxane-based prepolymers. It was found that it not only gave high oxygen permeability, but also gave hydrogels with better tear strength and lower modulus. These changes in properties are all favorable for applications such as oxygen-permeable hydrogel lenses. © 1995 John Wiley & Sons, Inc.     

温度及pH值双重敏感性水凝胶研究进展

综述近年来在温度及pH值双重敏感水凝胶研究方面的进展,简要介绍了此类水凝胶的合成、性能及其在药物控制释放方面的应用。     

Near‐Infrared Light‐Triggered Dual Drug Release Using Gold Nanorod‐Embedded Thermosensitive Nanogel‐Crosslinked Hydrogels

Gold nanorod (AuNR)‐embedded poly(N‐isopropylacrylamide) (PNIPAM) hydrogels offer the possibility of achieving near‐infrared (NIR) light‐triggered drug release. In addition, using nanoparticles as a crosslinker can enhance the mechanical properties of PNIPAM hydrogels, and nanoparticle‐crosslinked hydrogels provide an important approach for dual drug release. Here, NIR light‐triggered dual drug release using AuNR‐embedded thermosensitive nanogel‐crosslinked hydrogels is reported for the first time. Two kinds of drugs are encapsulated, one in the nanogel and the other in the hydrogel. The volume phase transition of the PNIPAM hydrogels is induced by NIR light by utilizing the photothermal effect of AuNRs. By changing the number of embedded AuNRs and the intensity of NIR light, the release rate and drug quantity can be adjusted for on‐demand release. Because of its NIR light‐triggering and nanoparticle‐crosslinking capabilities, AuNR‐embedded thermosensitive nanogel‐crosslinked hydrogels may expand the application scope of hydrogels and provide enhanced properties in their applications.     

Precision Control of Programmable Actuation of Thermoresponsive Nanocomposite Hydrogels with Multilateral Engineering

Hydrogels capable of stimuli-responsive deformation are widely explored as intelligent actuators for diverse applications. It is still a significant challenge, however, to “program” these hydrogels to undergo highly specific and extensive shape changes with precision, because the mechanical properties and deformation mechanism of the hydrogels are inherently coupled. Herein, two engineering strategies are simultaneously employed to develop thermoresponsive poly(N-isopropyl acrylamide) (PNIPAm)-based hydrogels capable of programmable actuation. First, PNIPAm is copolymerized with poly(ethylene glycol) diacrylate (PEGDA) with varying molecular weights and concentrations. In addition, graphene oxide (GO) or reduced graphene oxide (rGO) is incorporated to generate nanocomposite hydrogels. These strategies combine to allow the refined control of mechanical and diffusional properties of hydrogels over a broad range, which also directly influences variable thermoresponsive actuation. It is expected that this comprehensive design principle can be applied to a wide range of hydrogels for programmable actuation.     

ATRP in the design of functional materials for biomedical applications

Atom Transfer Radical Polymerization (ATRP) is an effective technique for the design and preparation of multifunctional, nanostructured materials for a variety of applications in biology and medicine. ATRP enables precise control over macromolecular structure, order, and functionality, which are important considerations for emerging biomedical designs. This article reviews recent advances in the preparation of polymer-based nanomaterials using ATRP, including polymer bioconjugates, block copolymer-based drug delivery systems, cross-linked microgels/nanogels, diagnostic and imaging platforms, tissue engineering hydrogels, and degradable polymers. It is envisioned that precise engineering at the molecular level will translate to tailored macroscopic physical properties, thus enabling control of the key elements for realized biomedical applications.     

Thermo- and pH-responsive HPC-g-AA/AA hydrogels for controlled drug delivery applications

This paper describes smart hydrogels composed of pH-sensitive poly(acrylic acid) (PAA) and biodegradable temperature-sensitive hydroxypropylcellulose-g-acrylic acid (HPC-g-AA) for controlled drug delivery applications. In a pH-responsive manner, the hydrogels with the higher HPC-g-AA content resulted in the lower equilibrium swelling. Although temperature had little influence on the swelling of the hydrogels, optical transmittance of the hydrogels was changed as a function of temperature, which reflecting that the HPC parts of hydrogel became hydrophobic at temperature above the lower critical solution temperature (LCST). Scanning electron microscopic analysis revealed that the pore size and the morphology of the hydrogels could be controlled by changing the composition of AA and the crosslinking density. Using BSA as a model drug, in vitro drug release experiment was carried out in artificial gastric juice (pH = 1.2) for the first 2 h and then in artificial intestinal liquid (pH = 6.8) for the subsequent 6 h. The release profiles indicated that both HPC-g-AA and AA contents played important roles in the drug release behaviors. The temperature- and pH-responsive HPC-g-AA/AA hydrogels might be exploited for wide applications in controlled drug delivery.