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2010 | Buch

Introduction to Hydrogels Kapitel lesen Erstes Kapitel lesen

Biomedical Applications of Hydrogels Handbook

herausgegeben von: Raphael M. Ottenbrite, Kinam Park, Teruo Okano

Verlag: Springer New York

Enthalten in: Springer Professional "Wirtschaft+Technik" , Springer Professional "Technik" , Springer Professional "Wirtschaft"

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Über dieses Buch

Hydrogels are networks of polymer chains which can produce a colloidal gel containing over 99 per cent water. The superabsorbency and permeability of naturally occurring and synthetic hydrogels give this class of materials an amazing array of uses. These uses range from wound dressings and skin grafts to oxygen-permeable contact lenses to biodegradable delivery systems for drugs or pesticides and scaffolds for tissue engineering and regenerative medicine. Biomedical Applications of Hydrogels Handbook provides a comprehensive description of this diverse class of materials, covering both synthesis and properties and a broad range of research and commercial applications. The Handbook is divided into four sections: Stimuli-Sensitive Hydrogels, Hydrogels for Drug Delivery, Hydrogels for Tissue Engineering, and Hydrogels with Unique Properties.

Key Features:

Provides comprehensive coverage of the basic science and applications of a diverse class of materials Includes both naturally occurring and synthetic hydrogels Edited and written by world leaders in the field.

Inhaltsverzeichnis

Frontmatter

Introduction to Hydrogels

Introduction to Hydrogels
Abstract
Hydrogels are a class of crosslinked polymers that, due to their hydrophilic nature, can absorb large quantities of water. These materials uniquely offer moderate-to-high physical, chemical, and mechanical stability in their swollen state. The structure of a hydrogels can be designed for a specific application by selecting proper starting materials and processing techniques. Since the equilibrium swelling capacity of a hydrogels is a balance between swelling and elastic forces, hydrogels with different swelling capacities can be designed by modulating the contribution of individual forces. Certain hydrogels respond to the changes in environmental factors by altering their swelling behavior. This chapter explains the evolution of hydrogels as a new class of the crosslinked polymers, the hydrogels structures, swelling forces, swelling kinetics, types of water in a swollen hydrogels, and composite properties of hydrogels materials.
Hossein Omidian, Kinam Park

Stimuli-Sensitive Hydrogels

Frontmatter
Stimuli-Responsive Hydrogels and Their Application to Functional Materials
Abstract
Many kinds of stimuli-responsive polymer gels that respond to the change in their surroundings such as solvent composition, temperature, pH, and supply of electric field have been developed. They are of interest as intelligent (or smart, biomimetic) materials which have sensor, processor, and actuator functions. This article is related to stimuli-­responsive gels and their application for bio- or biomimetic materials designed as self-oscillating gels.
Ryo Yoshida, Teruo Okano
Feedback Control Systems Using Environmentally and Enzymatically Sensitive Hydrogels
Abstract
A large number of hydrogels can be classified as smart materials that offer a natural integration of sensing, actuating, and regulating functions applicable to feedback control systems. This multifunctionality added to biocompatibility and enzyme-based selectivity characteristics enables self-regulation or implicit control in hydrogels-based devices to maintain physiological variables at a desired level or range by appropriate drug release. Therefore, hydrogels can enhance the performance of individual actuator and sensing units. Applications of hydrogels in explicit and implicit controller systems are presented based on recent experimental and theoretical research studies. Integration of cascade and feedforward control types of functionalities in hydrogels systems is suggested from their capability to respond to more than one stimulus. Enzymatic glucose sensing and insulin delivery are often used as references for the discussion of hydrogels in the development of sensor, actuator, and control technology due to the relevance of the diabetes disease.
Irma Y. Sanchez, Nicholas A. Peppas
Biomolecule-Responsive Hydrogels
Abstract
Biomolecule-responsive hydrogels that exhibit volume changes in response to target biomolecules have become increasingly important because of their potential applications as smart biomaterials. Researchers are developing novel biomedical systems using glucose, proteins and other biomolecule-responsive hydrogels as biosensing systems for applications such as drug delivery and cell culture systems. In the synthesis of biomolecule-responsive hydrogels, both biomolecular recognition and responsive functions that perceive a target biomolecule and induce structural changes must be introduced into the hydrogels network. Many biomolecule-responsive hydrogels are prepared by combining structural designs of hydrogels networks with molecular recognition events of biomolecules, such as enzymes, lectins and antibodies. Most important is the need to synthesize and develop more biomolecule-responsive hydrogels in tandem with their biomedical applications so that the field continues to evolve.
Takashi Miyata
Stimuli-Responsive PEGylated Nanogels for Smart Nanomedicine
Abstract
PEGylated nanogels are composed of cross-linked polyamine gels core with tethered PEG chains. The stimuli-responsive PEGylated nanogels have significant volume phase transitions in response to the extracellular pH (7–6.5) of a tumor environment as well as endosomal/lysosomal pH (6.5–5.5). The pH-responsive PEGylated nanogels containing 19F compounds in the polyamine gels core have remarkable on–off 19FMR signals (T 2 values of 19F) and signal-to-noise (S/N) ratio in response to the extracellular of tumor environment, making these nanogels effective as tumor-specific smart 19F MRI (magnetic resonance imaging) nanoprobes. The doxorubicin (DOX)-loaded pH-responsive PEGylated nanogels release DOX intracellular in response to endosomal/lysosomal pH, thereby conferring more antitumor activity than free DOX against naturally drug-resistant human hepatoma cells. The PEGylated nanogel with gold nanoparticles as the fluorescence quencher in the core and fluorescence dye-labeled DEVD (Asp-Glu-Val-Asp) peptide at the tethered PEG chain end provide pronounced fluorescence signals in response to apoptotic cells. Thus, stimuli-responsive PEGylated nanogels can be utilized as smart nanomedicines for cancer diagnosis and therapy.
Motoi Oishi, Yukio Nagasaki
Stimuli-Sensitive Microhydrogels
Abstract
Microhydrogels have become a very interesting and important material in hydrogels ­bioapplications. New techniques for the design, synthesis, characterization, function, and application of microhydrogels are providing exciting new possibilities in the micronized ­science. Hydrogels are a soft material with sizes and shapes that are subject to change depending on environmental conditions such as temperature, pH, coexisting materials, and light. Hydrogels that respond to these environmental stimuli and cause swelling changes in aqueous media are known as “stimuli-sensitive hydrogels.”
Haruma Kawaguchi

Hydrogels For Drug Delivery

Frontmatter
In-Situ Gelling Stimuli-Sensitive PEG-Based Amphiphilic Copolymer Hydrogels
Abstract
In-situ gelling stimuli-sensitive block copolymer hydrogels exhibit sol–gel phase-transitions in response to external stimuli, due to the formation of reversible polymer networks caused by physical interactions. In-situ gelling stimuli-sensitive block copolymer hydrogels show many advantages, such as simple drug formulation and administration procedures, no organic solvent, site-specificity, a sustained drug release behavior, less systemic toxicity, and ability to delivery both hydrophilic and hydrophobic drugs. Poly(ethylene glycol)s with relatively low molecular weight are hydrophilic, nontoxic, absent of antigenicity and immunogenicity, and can be directly excreted by the kidneys. PEG-based amphiphilic copolymers have attracted extensive interest for their unique self-assembly and biocompatibility. The PEG-based amphiphilic copolymers exhibit unique changes in micellar architecture and aggregation number in response to changes near physiological temperature; therefore, in-situ gelling systems made of the PEG-based amphiphilic copolymers have received worldwide investigation. This article stresses the recent development and biomedical evaluation of the in-situ gelling stimuli-sensitive PEG-based amphiphilic copolymers that are capable of responding to changes in temperature and/or pH.
Doo Sung Lee, Chaoliang He
Biodegradable Hydrogels for Controlled Drug Release
Abstract
Biodegradable hydrogels for controlled drug release are based on functionalized polymer systems and are of great importance in polymer therapeutics. The most relevant aspects of biodegradable polymeric hydrogels for the release of specific drugs and bio-active compounds are the nature of biodegradable polymer, the gelation process by physical or chemical crosslinking, and the properties of the bioactive compound. The design of bio-degradable hydrogels for drug delivery is an important aspect in the administration of therapeutics, such as the formulation and application of injectable hydrogels, are discussed on the basis of components and bioactive counterparts.
Luis García, María Rosa Aguilar, Julio San Román
Thermo-Responsive Biodegradable Hydrogels from Stereocomplexed Poly(lactide)s
Abstract
Hydrogels that form by responding to temperature changes are used for injectable biomaterials with many potential applications. Numerous techniques have been used to prepare biodegradable polymers for bioapplications. Specifically, biocompatible hydrogels that can be safely injected without surgery and sustained/disintegrated in a controlled manner are of interest. Poly(lactide), PLA, is the most studied and utilized biodegradable polymer, and its block copolymers provide a great variety of structures and properties. Utilizing stereocomplexation technology of enantiomeric PLAs on thermo-sensitive hydrogels of PLA–PEG block copolymers is an important aspect of bioapplications of hydrogels.
Tomoko Fujiwara, Tetsuji Yamaoka, Yoshiharu Kimura
Hydrogels-Based Drug Delivery System with Molecular Imaging
Abstract
Drug delivery systems with molecular imaging capability are usually nanoscopic therapeutic systems that incorporate therapeutic agents and diagnostic imaging probes. ­Polymers (which form hydrogels) and molecular imaging probes used currently were reviewed firstly. ­Polymer-coated molecular imaging probes were also reviewed to introduce the ­basic com­ponent in the preparation of drug delivery systems with molecular imaging capability. Finally, the recent studies on the drug delivery systems with molecular imaging capability were summarized and their prospect was addressed.
Keun Sang Oh, Soon Hong Yuk

Hydrogels for Tissue Engineering

Frontmatter
Hydrogels for Tissue Engineering Applications
Abstract
Hydrogels have been widely applied in biomedical applications, such as drug delivery and tissue engineering, due to their many favorable characteristics. Their high water content renders them compatible with living tissues and proteins and their rubbery nature minimizes damage to the surrounding tissue. Their mechanical properties parallel those of soft tissues, making them particularly appealing for engineering of these tissues. Hydrogels used in tissue engineering are preferably biodegradable, thus further surgery, after the hydrogels has performed its function, is not required. Also, biodegradable hydrogels allow for the replacement of the hydrogels over time by the extracellular matrix produced when cells are incorporated. The biofunctionality of hydrogels is essential to guide cellular behavior such as proliferation, differentiation, and matrix production. An on-demand biofunction can be obtained by the incorporation of growth factors into hydrogels to enhance cellular prolife­ration in the tissue-engineered matrices.
Rong Jin, Pieter J. Dijkstra
Composite Hydrogels for Scaffold Design, Tissue Engineering, and Prostheses
Abstract
Hydrogels have been successfully used in several biomedical applications, such as controlled drug release and micro-patterning. More recently, the ability to engineer composite hydrogels has generated new opportunities in addressing challenges in tissue engineering as well as in tissue function restoration via prostheses. Indeed, the knowledge of biocompatible materials and preparation technologies may be efficaciously used in synthesizing biocompatible hydrogels to develop state-of-the-art hydrogel-based devices for tissue regeneration and reconstruction. Important details with respect to the design of the materials adopted and with respect to specific tissues, such as tendons and ligaments, intervertebral discs, bone, menisci, and cartilage will be discussed.
V. Guarino, A. Gloria, R. De Santis, L. Ambrosio
Hydrogels for Cartilage Tissue Engineering
Abstract
Tissue engineering is an emerging field of regenerative medicine that holds promise for the restoration of tissues and organs affected by chronic diseases, age-linked degeneration, congenital deformity, and trauma. Tissue engineering consists of building tissue and organs using cells grown on natural or artificial biomaterials outside the body. Recent efforts in bone and cartilage tissue regeneration have turned to tissue engineering, which have shown the proof of concept in clinical situations. Articular cartilage is composed of 70–80% of water retained in the form of a stable macromolecular gels. The extracellular matrix (ECM) and chondrocytes represent 20–30% of the articular cartilage. The lack of vascularization of the articular cartilage, however, prevents the development of an inflammatory response; this severely limits spontaneous repair. Currently, research is being directed to cell therapy associated with specific scaffold-like hydrogels. Articular cartilage, in particular, is considered to be a good candidate for tissue engineering, because it requires less metabolic involvement due to lower cellularity and avascular matrix. Cartilage organization and pathology have been highlighted here with respect to scaffold strategies using synthetic hydrogels as biomimetic extracellular matrices for tissue engineering.
Pierre Weiss, Ahmed Fatimi, Jerome Guicheux, Claire Vinatier
Gelatin-Based Hydrogels for Controlled Cell Assembly
Abstract
Controlled cell assembly technique is a new research area in complex organ development technologies. Gelatin-based hydrogels, such as gelatin, gelatin/alginate, gelatin/chitosan, gelatin/fibrinogen, gelatin/hyaluronan, and gelatin/alginate/fibrinogen, have played an important role in the rapid fabrication of tissue or organs with well-defined structures and functions. Cryoprotectants, such as dimethylsulfoxide (DMSO) and glycerol, can be easily incorporated into the system for long-term conservation of the cell containing constructs. Hepatocytes, chondrocytes, cardiac myocytes, and adipose-derived stromal cells (ADSCs) are used to show function of the assembled cells. ADSCs can be controlled to differentiate into different targeted cell types according to their positions within the orderly predesigned three-dimensional (3D) constructs. A multicellular model for the metabolic syndrome was established along with the development of the double-syringe deposition system which lead to a hybrid cell/hydrogels construct with a vascular-like network fabricated using a digital model. The preliminary results indicate that the double-syringe assembly technique is a powerful tool for fabricating complex constructs with special intrinsic/extrinsic structures, and has the potential to be widely used in regenerative medicine and drug screening.
Xiaohong Wang, Yongnian Yan, Renji Zhang
Double Network Hydrogels as Tough, Durable Tissue Substitutes
Abstract
Hydrogels are soft and wet materials with a wide range of biomedical applications to make tissue due to their unique properties, such as phase-transition, chemo-mechanical behavior, stimuli-responsiveness, and low surface friction. However, most hydrogels are mechanically too weak to be used practically in load-bearing applications. Double Network (DN) hydrogels are composed of both rigid and soft hydrogels networks, and are expected to perform better under mechanical loads. The DN gels exhibit a 0.1–1 MPa elastic modulus, 60 MPa compressive fracture stress, 3,000% of tensile strain, and 2,500 J/m2 of fracture energy. These soft and wet gels materials with high mechanical strength, low surface friction, and high deterioration-resistance properties are good candidates as load-bearing tissue substitutes, such as auricular cartilage.
Takayuki Murosaki, Jian Ping Gong
Hydrogels Contact Lenses
Abstract
Contact lenses can be classified in a number of ways; however, the two main categories are hard and soft lenses, which are based on the material used for their manufacture. The soft lens category can be further divided into hydrophobic and hydrophilic subcategories. Consequently, the development of contact lens materials took three specific directions: hydrogels with high water content, rigid gas-permeable lenses with enhanced oxygen permeability, and surface modification of silicone elastomer lenses. These polymeric systems are expected to improve the water content of the contact lenses as well as the permeability to oxygen, which are crucial properties but controllable through the molecular design. Currently, the high water content hydrogels are being challenged by the silicone-hydrogels for the world market share.
Jiri Michalek, Radka Hobzova, Martin Pradny, Miroslava Duskova

Hydrogels With Unique Properties

Frontmatter
Electroconductive Hydrogels
Abstract
Methods for the synthesis of electroconductive hydrogels (ECH), as polymer blends and as polymer conetworks via chemical oxidation, electrochemical, or a combination of chemical oxidation followed by electrochemical synthesis techniques, are described. Specific examples are introduced to illustrate the preparation of ECHs synthesized from poly(HEMA)-based hydrogels and polyaniline or from poly(HEMA)-based hydrogels and polypyrrole. The key applications of ECHs, as biorecognition membranes for implantable biosensors, as electrostimulated drug eluting devices, and as the low interfacial impedance layer on neuronal prostheses, provide great new horizons for biodetection devices.
Ann M. Wilson, Gusphyl Justin, Anthony Guiseppi-Elie
Self-assembled Nanogel Engineering
Abstract
Functional nanogels have been designed by the self-assembly of various associating polymers. In particular, cholesterol-bearing polysaccharides form physically crosslinked nanogels by self-assembly in water. The nanogels trap proteins mainly by hydrophobic interaction and show chaperon-like activity. They are useful as polymeric nanocarriers especially in protein delivery. Macrogels with well-defined nanostructures were obtained by self-assembly and chemical crosslinking of these nanogels as building blocks.
Nobuyuki Morimoto, Kazunari Akiyoshi
Engineered High Swelling Hydrogels
Abstract
High swelling hydrogels (HSHs) are materials with the ability to swell to a large size in an aqueous medium. The swelling feature and mechanical properties of the HSH polymers depend on many factors. Therefore, the HSH properties can be engineered to tailor a hydrogels for a specific application. This chapter begins with the HSH anatomy and its engineering aspects, and continues with the purity of hydrogels and the sources of impurities in HSH polymers. The characterization of HSH polymers includes swelling determination, mechanical properties, and analytical issues, which will be discussed with a focus on both practical and theoretical aspects. Since final hydrogels properties are closely related to the level of its stability, this aspect is discussed by explaining the sources of instability, which potentially threaten the hydrogels properties. The chapter ends with two important groups of hydrogels that have been suggested and engineered for specific applications in pharmaceutical area.
Hossein Omidian, Kinam Park
Superabsorbent Hydrogels
Abstract
Superabsorbent hydrogels have unique swelling features that are highly attractive for biomedical, pharmaceutical, and industrial applications. The swelling capacity of many hydrogels, however, is very sensitive to the pH and ionic strength of the solution. Acids and bases, as well as salts (monovalent, multivalent) can significantly affect the solution properties of these polymers. Therefore, it is essential to understand the swelling phenomena of hydrogels, such as the forces responsible for the swelling and swelling barriers. Since the swelling rate of hydrogels is basically required for most applications, detailed information with respect to the swelling kinetics in hydrogels is important as well as the theoretical aspects of swelling mechanisms, especially in solutions containing salts.
Grigoriy Mun, Ibragim Suleimenov, Kinam Park, Hossein Omidian
Backmatter
Metadaten
Titel
Biomedical Applications of Hydrogels Handbook
herausgegeben von
Raphael M. Ottenbrite
Kinam Park
Teruo Okano
Copyright-Jahr
2010
Verlag
Springer New York
Electronic ISBN
978-1-4419-5919-5
Print ISBN
978-1-4419-5918-8
DOI
https://doi.org/10.1007/978-1-4419-5919-5

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