Alginates E-Book
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- Herausgeber: John Wiley & Sons
- Kategorie: Fachliteratur
- Sprache: Englisch
Alginate is a hydrophilic, biocompatible, biodegradable, and relatively economical polymer generally found in marine brown algae. The modification in the alginate molecule after polymerization has shown strong potential in biomedical, pharmaceutical and biotechnology applications such as wound dressing, drug delivery, dental treatment, in cell culture and tissue engineering. Besides this, alginates have industrial applications too in the paper and food industries as plasticizers and additives.
The few books that have been published on alginates focus more on their biology. This current book focuses on the exploration of alginates and their modification, characterization, derivatives, composites, hydrogels as well as the new and emerging applications.Sie lesen das E-Book in den Legimi-Apps auf:
Seitenzahl: 514
Veröffentlichungsjahr: 2019
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Contents
Cover
Title page
Copyright page
Dedication
Preface
Part 1: Alginates—Introduction, Characterization and Properties
Chapter 1: Alginates: General Introduction and Properties
1.1 Introduction
1.2 History
1.3 Structure
1.4 Alginates and Their Properties
1.5 Sources
1.6 Biosynthesis of Bacterial Alginate
1.7 Conclusion
Acknowledgment
Conflict of Interests
References
Chapter 2: Alginates Production, Characterization and Modification
2.1 Introduction
2.2 Alginate: Production
2.3 Characterization of Physicochemical Properties of Alginate
2.4 Modification of Alginates
2.5 Future Perspectives
2.6 Conclusions
References
Chapter 3: Alginate: Recent Progress and Technological Prospects
3.1 Introduction
3.2 Structure
3.3 Sources
3.4 Characteristics of Alginate Salts
3.5 Properties
3.6 Applications
3.7 Future Perspectives
3.8 Advantages
3.9 Disadvantages
3.10 Conclusion
Acknowledgments
References
Chapter 4: Alginate Hydrogel and Aerogel
4.1 Introduction
4.2 Alginate Hydrogel
4.3 Alginate Aerogel
4.4 Future Perspectives
References
Part 2: Alginates in Biomedical Applications
Chapter 5: Alginate in Biomedical Applications
5.1 Introduction
5.2 Chemical Structure and Properties of Alginate
5.3 Types of Interaction of Alginate
5.4 Biomedical Application of Alginates
5.5 Future Perspective of the Use and Biomedical Applications
References
Chapter 6: Alginates in Pharmaceutical and Biomedical Application: A Critique
6.1 Introduction
6.2 Structure of Alginate
6.3 Different Types of Alginates Used in Pharmaceutical Industries
6.4 Properties of Alginate
6.5 Pathway for the Biosynthesis of Alginate
6.6 Regulatory Consideration of Alginate
6.7 Applications
6.8 Conclusion
References
Chapter 7: Alginates in Evolution of Restorative Dentistry
7.1 Introduction
7.2 Method of Alginate Extraction
7.3 Evolution of Alginate in Restorative Dentistry
7.4 The Art of Impression Taking Using Alginates
7.5 Conclusions
References
Chapter 8: Alginates in Drug Delivery
8.1 Introduction
8.2 Chemistry of Alginates
8.3 Pharmaceutical and Biomedical Chemistry of Alginates
8.4 Conclusions
Acknowledgments
References
Chapter 9: Alginate in Wound Care
9.1 Introduction
9.2 Sources and Synthesis of Alginate
9.3 Physicochemical Properties of the Alginate Biopolymer
9.4 Biomedical Applications of Alginate
9.5 Opportunities and Future Thrust
References
Chapter 10: Alginate-Based Biomaterials for Bio-Medical Applications
10.1 Introduction
10.2 Alginate: General Properties
10.3 Extraction and Preparation
10.4 Alginate Hydrogels
10.5 Photocross-Linking
10.6 Shape-Memory Alginate Scaffolds
10.7 Biodegradation of Alginate
10.8 Biomedical Application of Alginates
References
Part 3: Alginates in Food Industry
Chapter 11: Alginates for Food Packaging Applications
11.1 Introduction
11.2 Biopolymer in Food Industry
11.3 Alginates in Food Packaging
11.4 Biosynthesis of Alginate
11.5 Application of Alginate in Formation of Biofilm
11.6 Packaging Properties of Alginate
11.7 Effect of Alginate on the Quality of Food
11.8 Interaction between Food and Alginates
11.9 Environmental Effects on Alginate Packaging
11.10 Market Outlook
11.11 Conclusion
References
Chapter 12: Potential Application of Alginates in the Beverage Industry
12.1 Introduction
12.2 Alginate Source
12.3 Extraction of Alginates
12.4 Physical, Chemical and Functional Properties of Alginate
12.5 Uses as a Food Additive/Ingredient
12.6 Alginate as Stabilizer
12.7 As Encapsulating Wall Material
12.8 Conclusion
References
Chapter 13: Alginates in Comestibles
13.1 Introduction
13.2 Alginates in Agricultural Marketing
13.3 Use of Alginates in Food Industry
13.4 Use of Alginates for Pets
13.5 Effect of Dietary Alginates
13.6 Alginate Safety
13.7 Conclusion
References
Part 4: Alginates Future Prospects
Chapter 14: Alginates: Current Uses and Future Perspective
14.1 Introduction
14.2 Sources of Alginate Synthesis
14.3 Synthesis of Alginate
14.4 Properties of Alginates
14.5 Application of Alginates
14.6 Future Perspectives of Alginates
14.7 Conclusion
References
Index
End User License Agreement
Guide
Cover
Copyright
Table of Contents
Begin Reading
List of Illustrations
Chapter 1
Figure 1.1
Structure of ALG monomers (L-guluronic acid and D-mannuronic acid).
Figure 1.2
(a) Homopolymeric blocks of poly-β-1,4-D-mannuronic acid (MM blocks);...
Figure 1.3
Egg-box structure formation during the ionic gelation of sodium ALG [17]....
Figure 1.4
Gelation process of ALG [25]....
Figure 1.5
Structure of the ALG biosynthetic complex [33]....
Chapter 2
Figure 2.1
Oxidation of sodium alginate....
Figure 2.2
Copolymerization of sodium acrylate with sodium alginate....
Figure 2.3
Esterification of alginate....
Figure 2.4
Alginate cross-linking using epichlorohydrin....
Figure 2.5
Alginate cross-linking using glutaraldehyde....
Chapter 3
Figure 3.1
Alginate monomers in block distribution....
Figure 3.2
Procedure of alginate....
Chapter 6
Figure 6.1
Structure of alginate showing all four glycosidic linkages, i.e., linkage in MM,...
Figure 6.2
Sodium alginate extraction from brown algae....
Figure 6.3
Flow chart for the production of sodium alginate....
Chapter 7
Figure 7.1
Chemical structure of alginate (adopted from Skaugrud, Hagen [11])....
Figure 7.2
Cross-linking of alginate G blocks with calcium....
Figure 7.3
Method of sodium alginate extraction from brown seaweed (adapted from Sachan,...
Chapter 8
Figure 8.1
(a) Different forms of linear polymers of alginate [1]. (b) L-guluronic acid (G)...
Figure 8.2
Different mechanisms of drug release (reproduced with permission [9])....
Chapter 9
Figure 9.1
Bacterial alginate biosynthesis pathway [11]....
Figure 9.2
Structural characteristics of alginates: (a) alginate monomers, (b) chain...
Figure 9.3
Possible junction points in alginates. (a) GG/GG junctions, (b) MG/MG junctions,....
Figure 9.4
Cross-sectional images of regeneration of rat deep wound model stained by...
Figure 9.5
Swelling capacity of PEGDA/AA/alginate hydrogels with different monomer...
Figure 9.6
Photographic findings of wounds covered with ACF-HS or Kaltostat, and controls....
Figure 9.7
Histology of wound sections stained with hematoxylin and eosin. Epithelialization...
Chapter 10
Figure 10.1
The (1-4)-linkage of alternate M and G residues of alginate [11]....
Figure 10.2
The intermolecular cross-linkage of G residues of alginate with Ca2+ ions [12]....
Figure 10.3
Preparation and extraction of alginate from natural resources....
Figure 10.4
Images of optical microscopic C
2
C
12
myoblasts linked to the...
Figure 10.5
Images of confocal microscopic main human fibroblasts cultivated on alginate gels...
Chapter 11
Figure 11.1
Schematic overview of different biopolymers [15]....
Figure 11.2
Conformations of M- and G-blocks [20]....
Figure 11.3
Block structures of alginates. Poly-β-D-mannuronate (above) and...
Figure 11.4
Scanning electron micrograph of alginate cast film [17]....
Figure 11.5
Schematic cross-linking of alginate in the presence of calcium counterions...
Figure 11.6
Effect of antimicrobial plastic film on
Aspergillus niger.
Agar...
Chapter 12
Figure 12.1
Schematic representation of commercial extraction of alginates....
Figure 12.2
Production of propylene glycol alginate: Reaction between alginic acid and propylene...
Figure 12.3
Structural characteristics of alginates: (a) monomers, (b) chain conformation,...
Figure 12.4
Egg box complex of Ca
2+
ion and alginate (modified from [25])....
Figure 12.5
External ionic gelation through extrusion (Source: modified from [9])....
Figure 12.6
Internal setting method (Source: modified from [9])....
Figure 12.7
Microencapsulation of probiotic culture by external and internal ionic gelation...
Chapter 14
Figure 14.1
Structure of mannuronate, guluronate, and β (1→4) mannuronic acid...
Figure 14.2
Gene order of alginate synthesis genes—(a) biosynthesis genes, (b)...
List of Tables
Chapter 6
Table 6.1
Characteristics of sodium alginate recommended by the United States Pharmacopeia...
Table 6.2
List of pharmaceutical products based on ALG....
Chapter 7
Table 7.1
Studies on the effect of extended pour time on dimensional stability of the...
Chapter 9
Table 9.1
Alginate-based wound dressings commercially available in the market [21]....
Table 9.2
Different hydrophilic polymers for preparation of hydrogel [58]....
Chapter 11
Table 11.1
Application of alginate in food packaging....
Chapter 12
Table 12.1
Grades of alginates extracted from various seaweeds in their country of harvest...
Table 12.2
Solubility of alginates in various pH solutions [18]....
Table 12.3
Various applications of alginates and its purpose of use (Source: modified from...
Table 12.4
Permissible limit for alginates in different food products (Source: modified...
Table 12.5
Multilayer encapsulation of various probiotic microbes with multilayer wall...
Chapter 13
Table 13.1
Approval of alginates by various food committees....
Chapter 14
Table 14.1
Algae used for the extraction of alginates....
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Scrivener Publishing100 Cummings Center, Suite 541JBeverly, MA 01915-6106
Publishers at ScrivenerMartin Scrivener ([email protected])Phillip Carmical ([email protected])
Alginates
Applications in the Biomedical and Food Industries
Edited by
Shakeel Ahmed
This edition first published 2019 by John Wiley & Sons, Inc., 111 River Street, Hoboken, NJ 07030, USA and Scrivener Publishing LLC, 100 Cummings Center, Suite 541J, Beverly, MA 01915, USA © 2019 Scrivener Publishing LLC For more information about Scrivener publications please visit www.scrivenerpublishing.com.
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Library of Congress Cataloging-in-Publication Data
ISBN 978-1-119-48791-3
This book is dedicated to:
The woman who raised me—AmmaThe woman who guided me—Prof Saiqa IkramThe women who loved me—Nasreen Akhter, Parveen Akhter, ShamimAkhter, and Naida BhabhiThe men who supported me during ups and downs of my life—Mohd Shabbir, Abdul Hamid, Mohd Aslam, and Naseeb BajraanThe friends who stood with me—Wahid ul Rehman, Faheem Rasool,Aamir Mushtaq, and Maqbool Bajjar
Preface
Alginates are linear biopolymers consisting of 1,4-linked β-D-mannuronic acid and 1,4 α-L-guluronic acid residues. These groups of naturally occurring polysaccharides, which are derived from brown algal cell walls and several bacterial strains, have found numerous applications in biomedical sciences and pharmaceutical and food industries. Although there are currently many books available with chapters referencing alginates, this is the first of its kind solely devoted to their properties, modification, and characterization, with particular emphasis on their applications in the biomedical and food industries.
The wide-ranging topics discussed in this book are as follows. Chapter 1 gives an overview of alginates, their structures, and properties, and a detailed account of the modification of alginates, various characterization techniques, and methods of processing is given in chapter 2. Chapter 3 covers the dynamic properties of alginates and their innovative application in various materials, namely, the nanomaterial or the polymer. Chapters 4 and 5 discuss the biomedical applications of alginates. The focus of chapter 6 is the wide use of alginates in pharmaceutical and biomedical industries and that of chapter 7 is the evolution of alginate materials in restorative dentistry. Chapter 8 discusses applications of different cross-linked alginate networks, their microspheres, and hydrogel in relation to drug encapsulation and delivery processes and includes a brief introduction of the chemistry and pharmaceutical chemistry of alginates.
In chapter 9, biomedical applications of alginates—particularly wound care application in the various forms of alginate-based wound dressings—are discussed. Chapter 10 discusses the present use and future potential of alginates as a tool in drug formulation and regenerative medicine. Chapters 11, 12, and 13 focus on food packaging, beverage industry, and comestible applications of alginates, respectively. The last chapter of the book discusses the current uses and future prospects of alginates in food packaging and biomedical applications.
I hope that this book will be helpful to research scholars and scientists working in the area of alginates. I hope that it will also be helpful to beginners and undergraduate and graduate students, as it gives a full description of alginate structural details, history, properties, processing, etc. I am very grateful to the contributors of this book for their valuable contributions and Scrivener-Wiley for its publication.
Shakeel Ahmed December 2018 Jammu & Kashmir, India
Part 1ALGINATES—INTRODUCTION, CHARACTERIZATION AND PROPERTIES
Chapter 2Alginates Production, Characterization and Modification
Pintu Pandit1*, T. N. Gayatri1 and Baburaj Regubalan2
1Department of Fibres and Textile Processing Technology
2Department of Food Engineering and Technology, Institute of Chemical Technology, N. P. Marg, Matunga, Mumbai, India
*Corresponding author:[email protected]
Abstract
Alginate, naturally occurring in brown seaweeds, is an anionic polysaccharide that has been deeply researched, and its properties of biocompatibility with human tissue, bone, and teeth, and mild gelation along with minimal toxicity while being relatively cheap, have found application in many biomedical science and engineering products and processes. Globally, seaweeds provide the major raw material source for economically producing alginate and related polysaccharides and industrial products. The physicochemical properties of alginates vary as they are composed of various proportions of β-d-mannuronic acid (M) and α-l-guluronic acid (G) residues in their polymeric chains, measured by the G/M ratio, and the specific distribution of molecular weight of the different polymers in the product. The sequence and nature of extraction and precipitation procedures of alginates from seaweed species not only affect the purity and amount of yield but also control the chemical constitution and rheological properties of the product alginate. This chapter will provide a detailed overview of alginate’s production, characterization, and modification, which could indicate new starting points for future studies.
Keywords: Alginates, production, characterization, modification
2.1 Introduction
Alginate is an anionic polysaccharide, naturally occurring in brown seaweeds, and has been extensively studied and used in many biomedical applications due to its biocompatibility, minimal toxicity, and mild gelation achieved through addition of divalent cations such as Ca2+, along with its availability at a relatively cheap price [1]. Alginate hydrogels can be prepared by different cross-linking techniques and agents; depending on the nature of cross-linking and density of the network, drugs ranging in size from small molecules to large macromolecular proteins can be released in a controlled manner from the alginate gel, which encapsulates them or carries them. Their structure has features similar to the extracellular matrices of biological structural tissues promoting their extensive application in wound healing medical devices, cell transplantation and in the delivery of bioactive drugs and proteins. Alginate wound dressings favor wound healing by maintaining a physiologically moist microenvironment, while inhibiting bacterial infection at the wound site.
Alginate gels find important and numerous applications in the pharmaceutical field as they may be orally ingested or given as injections into the body, without causing much discomfort to the patient. In tissue engineering, cell and organ transplants and implants made from alginate gels provide a substitute for regeneration for patients with damaged, nonfunctioning organs and tissues [2]. Hydrogels function by carrying a payload of regenerative cells and drugs to the site of damage, while also acting as a substrate for the growth of new tissue, whose structure and function can be guided by the mechanical flexibility, stiffness, and pore size of the alginate gel [3].
Alginate has been utilized in biomedical applications such as wound healing, drug delivery, and in vitro cell culture and has unexplored potential as a biomaterial for many tissue engineering problems. The suitability and fit of alginate for these applications are because of its biocompatibility, gelation under mild conditions, and the ease of synthetic modifications required to make alginate derivatives that have the required properties. Chemically modified alginate has found a crucial use as a carrier for dental follicle cells and suitable growth factors to initiate and promote periodontal regeneration while sustaining osteogenesis [4]. Similar to other hydrogels from agarose, polyvinyl alcohol, and acrylates, alginate gels have a limited mechanical stiffness and degrade gradually on exposure to physiological fluids, and the more general physical properties of absorption, swelling, and ion and small molecule binding and release could be modulated with the structure and compositional variation. The encapsulation of cells by covalent cross-linking reactions can cause toxic harm to the cells encapsulated, but through a suitable choice of cell-compatible chemical reagents (e.g., initiator), and complete removal of unreacted reagents and by-products, cross-linked alginate can be fitted such applications. Looking to the future, the alginate-based materials used in medicine are likely to develop exponentially.
The clinical application of alginate gels in wound healing involves their passive role as resorbable matrices. The use and design of alginate gels as reservoirs of drugs and progenitor cells for growth, which release on external mechanical signals or tuned magnetic fields, is feasible [5, 6]. The ability of alginates to interact with cells is pivotal to tissue engineering applications, since without modification with protein signaling motifs, alginates are not recognized for mammalian cell adhesion. The nature of adhesion ligands and their spatial arrangement in gels are key parameters that can regulate and select the growth of cell phenotype in regenerated tissue, eventually determining its resultant function. Genetic engineering techniques to modify bacterial synthesis of alginates could forge new pathways to the design and creation of alginate polymers with tailor-made properties. Various polypeptides and proteins that improve structural properties and engender novel functions in alginate gels have been prepared and examined for biomedical applications [7, 8]. The ability to design and synthesize new classes of alginates with control of specific physical and chemical characteristics, unlike the limited range of properties available from natural alginate sources, tuned to a particular application could herald a revolution in the use of these materials. In this chapter, general properties, production, and modification of alginate have been discussed.
Biopolymer demand continues to grow annually by 3–4% because of their enhanced application in different areas, but production needs to keep pace with it. The annual growth rate over 2007–2011 in volume terms of seaweed produced has been 9%. Emerging producers in China, Eastern Europe, Brazil, etc. have driven most of this growth. Prices have tended to remain stable, even though demand has outstripped production because the markets do not support increased prices where substitution or extension with cheaper materials is possible. The higher seaweed material and process costs of energy and chemicals reflect the production of alginic acid on a large scale. The islands of the Philippines and Indonesia are the major producers of cultivated Laminaria digitata, Laminaria hyperborea, and Laminaria saccharina because their oceanic geography assists the growth of alginate-producing seaweed throughout the year. In comparison, in India, the available alginate produce much less and the viscosity of the produced alginate does not readily fit the requirements of the textile industry. Therefore, there is a great need to discover bacterial resources for alginate production with higher viscosity, which may be exploited with little capital cost. Production of alginate depends on the demand from various industries, and the viscosity of the alginate production can be enhanced, for example, by using recombinant strains of Azotobacter, obtained by genetic manipulation [9].
2.2 Alginate: Production
Seaweeds are the major source for producing value-added polysaccharides and industrial by-products globally. Alginates are one of the chief products extracted from seaweeds, mainly brown algae. These polysaccharides constitute the structural composition of the cell walls and the intercellular matrix in seaweeds.
The ratio M/G varies with the source of alginates, but its physical properties, for similar M/G ratio, are almost the same even when extracted from different biosources. Alginates are most often used in food processing as a stabilizer, viscosity agent, and gelling agent, with annual industrial requirements of alginates reaching ~30,000 metric tons [10]. Alginates form 40% of the dry matter of the commercially harvested species of seaweeds, such as Laminaria spp. and Macrocystis spp. [11]. Recently, this polysaccharide has been used for wide range of pharmaceutical and biological products, as in wound dressings [12]. Prior to 1975, commercial alginate production was based on seaweeds, where they were treated with alkali solution followed by filtration. The alginates were precipitated with chloride salts of sodium/calcium cations, so that the alginate salts can be converted to alginic acid, on acidifying with dilute HCl. On purification, the obtained alginic acid gave water-soluble sodium alginates [13]. During the late 1980s, two genera of bacteria, the nonpathogenic Pseudomonas and Azotobacter, were identified to be major producers of alginate and alginic acids. In nature, microbes produce alginates through different metabolic processes with various material functions. Pseudomonas aeruginosa produces alginates that constitute the thick highly structured biofilm, characteristic of the species [9], whereas Azotobacter produces rigid alginate, essential for the formation of water-conserving cysts [14] resistant to dessication and stress.
2.2.1 Screening of Alginate-Producing Microbes
Alginates are hydrocolloids derived from seaweed that interact with water to form colloid systems, like a gel or solubilized particles. Alginates are extracted in disparate ways depending on the application, but the most generally applied procedure [9] involves extracting the alginate as sodium alginate. The insoluble calcium and magnesium alginates present in the brown seaweed cell walls are extracted by maceration and converted to soluble sodium alginates, eventually obtained as alginic acid or calcium alginate. The consecutive addition of acid, alcohol, and sodium carbonate affects the conversion. The extraction procedures applicable to alginate extraction encounter problems such as insolubility from seaweed residuals interfering with the ease of separation. Filtration of the solution of dissolving alginate as sodium alginate requires large volumes of water, as the increased viscosity of the solution makes the separation onerous. The fine particulate nature of the seaweed residuals can block the filter; so filter aids are required to ease the process and make it cost effective. Also, the chemicals utilized for extraction influence the physicochemical properties of alginates. There exists a need to establish extraction and processing by alternate and milder methods, so as to overcome the problems faced in the traditional extraction procedures along with the detrimental effects on the quality and quantity of alginate yield. Enzymatic extraction techniques of alginate from seaweed using enzymes such as alginate lyase, laminarinase, which could degrade the seaweed cell wall to release free alginate, have been studied, but not standardized to routine extractions. The main hurdles facing alginate producers are the varying available areas for alginate farming and production due to increasing non-alginate uses for the same types of seaweed, increasing government proscriptions on the harvesting of natural seaweeds, and decreasing ease of access to large natural seaweed resources. Natural seaweed releases alginate alone into the surrounding sea water, but in the marine environment, it is converted to sodium salt of alginates. Hence, potassium alginate also is present in the extract from cells of marine seaweed. Calcium alginate is obtained from sodium alginate, where sodium is substituted with calcium.
