Chitosan Based Biomaterials Volume 1

Chitosan Based Biomaterials Volume 1
Author: Jessica Jennings
Publsiher: Woodhead Publishing
Total Pages: 390
Release: 2016-10-01
ISBN 10: 9780081002308
ISBN 13: 0081002300
Language: EN, FR, DE, ES & NL

Chitosan Based Biomaterials Volume 1 Book Review:

"Chitosan Based Biomaterials: Fundamentals, Volume 1, " provides the latest information on chitosan, a natural polymer derived from the marine material chitin. Chitosan displays unique properties, most notably biocompatibility and biodegradability. It can also be easily tuned to modify its structure or properties, making chitosan an excellent candidate as a biomaterial. Consequently, chitosan is being developed for many biomedical functions, ranging from tissue engineering and implant coatings to drug and gene delivery. This book looks at the fundamentals of chitosan-based biomaterials. Contains specific focus on the techniques and technologies needed to develop chitosan for biomedical applicationsPresents a comprehensive treatment of the fundamentalsProvides contributions from leading researchers with extensive experience in chitosan

Chitosan

Chitosan
Author: Shakeel Ahmed,Saiqa Ikram
Publsiher: John Wiley & Sons
Total Pages: 516
Release: 2017-08-04
ISBN 10: 1119364817
ISBN 13: 9781119364818
Language: EN, FR, DE, ES & NL

Chitosan Book Review:

This book delves deeply in to the preparation, characterization and multiple applications of chitin and chitosan. The 17 chapters written by leading experts is an excellent reference source and state-of-the-art review for researchers and scientists using chitosan or biopolymers in their respective areas. This book is divided into following sections: • Production and derivatives of chitosan • Chitosan in the textile and food industries • Chitosan in biomedical applications • Chitosan in agriculture and water treatment The book is practical as readers will be able to see descriptions of chitosan production methods as well as techniques that can be used to estimate and modify their physical and chemical properties. It provides a full description not only of the traditional and recent developments in the applications of chitosan in the fields of biotechnology, environmental studies, food, medicine, water treatments, drug delivery, but it includes all of the therapeutically usages as well.

Functional Chitosan

Functional Chitosan
Author: Sougata Jana,Subrata Jana
Publsiher: Springer Nature
Total Pages: 489
Release: 2020-04-10
ISBN 10: 9811502633
ISBN 13: 9789811502637
Language: EN, FR, DE, ES & NL

Functional Chitosan Book Review:

Thanks to their unique properties, chitosan and chitosan-based materials have numerous applications in the field of biomedicine, especially in drug delivery. This book examines biomedical applications of functional chitosan, exploring the various functions and applications in the development of chitosan-based biomaterials. It also describes the chemical structure of chitosan and discusses the relationship between their structure and functions, providing a theoretical basis for the design of biomaterials. Lastly, it reviews chemically modified and composite materials of chitin and chitosan derivatives for biomedical applications, such as tissue engineering, nanomedicine, drug delivery, and gene delivery.

Hydrogels

Hydrogels
Author: Lacramioara Popa,Mihaela Violeta Ghica,Cristina Dinu-Pirvu
Publsiher: BoD – Books on Demand
Total Pages: 132
Release: 2019-04-10
ISBN 10: 1789858755
ISBN 13: 9781789858754
Language: EN, FR, DE, ES & NL

Hydrogels Book Review:

Hydrogels, as three-dimensional polymer networks, are able to retain a large amount of water in their swollen state. The biomedical application of hydrogels was initially hampered by the toxicity of cross-linking agents and the limitations of hydrogel formation under physiological conditions. However, emerging knowledge in polymer chemistry and an increased understanding of biological processes have resulted in the design of versatile materials and minimally invasive therapies.The novel but challenging properties of hydrogels are attracting the attention of researchers in the biological, medical, and pharmaceutical fields. In the last few years, new methods have been developed for the preparation of hydrophilic polymers and hydrogels, which may be used in future biomedical and drug delivery applications. Such efforts include the synthesis of self-organized nanostructures based on triblock copolymers with applications in controlled drug delivery. These hydrogels could be used as carriers for drug delivery when combined with the techniques of drug imprinting and subsequent release. Engineered protein hydrogels have many potential advantages. They are excellent biomaterials and biodegradables. Furthermore, they could encapsulate drugs and be used in injectable forms to replace surgery, to repair damaged cartilage, in regenerative medicine, or in tissue engineering. Also, they have potential applications in gene therapy, although this field is relatively new.

Biological Activities and Application of Marine Polysaccharides

Biological Activities and Application of Marine Polysaccharides
Author: Emad Shalaby
Publsiher: BoD – Books on Demand
Total Pages: 328
Release: 2017-01-11
ISBN 10: 9535128590
ISBN 13: 9789535128595
Language: EN, FR, DE, ES & NL

Biological Activities and Application of Marine Polysaccharides Book Review:

Marine organisms have been under research for the last decades as a source for different active compounds with various biological activities and application in agriculture, pharmacy, medicine, environment, and industries. Marine polysaccharides from these active compounds are used as antibacterial, antiviral, antioxidant, anti-inflammation, bioremediations, etc. During the last three decades, several important factors that control the production of phytoplankton polysaccharides have been identified such as chemical concentrations, temperature, light, etc. The current book includes 14 chapters contributed by experts around the world; the chapters are categorized into three sections: Marine Polysaccharides and Agriculture, Marine Polysaccharides and Biological Activities, and Marine Polysaccharides and Industries.

Chitosan Based Biomaterials Volume 2

Chitosan Based Biomaterials Volume 2
Author: Jessica Amber Jennings,Joel David Bumgardner
Publsiher: Woodhead Publishing
Total Pages: 296
Release: 2016-09-28
ISBN 10: 0081002564
ISBN 13: 9780081002568
Language: EN, FR, DE, ES & NL

Chitosan Based Biomaterials Volume 2 Book Review:

Chitosan Based Biomaterials: Tissue Engineering and Therapeutics, Volume 2, provides the latest information on chitosan, a natural polymer derived from the marine material chitin. Chitosan displays unique properties, most notably biocompatibility and biodegradability. It can also be easily tuned to modify its structure or properties, making chitosan an excellent candidate as a biomaterial. Consequently, chitosan is being developed for many biomedical functions, ranging from tissue engineering and implant coatings to drug and gene delivery. This book provides readers with a full coverage of the applications of chitosan-based biomaterials. Presents specific focus on tissue engineering and therapeutics Provides comprehensive treatment of all biomaterial applications of chitosan Contains contributions by leading researchers with extensive experience in the material

Chitin and Chitinases

Chitin and Chitinases
Author: Pierre Jollès (prof. dr.),Riccardo A. A. Muzzarelli
Publsiher: Unknown
Total Pages: 340
Release: 1999
ISBN 10:
ISBN 13: UOM:39015048536927
Language: EN, FR, DE, ES & NL

Chitin and Chitinases Book Review:

Handbook of Chitin and Chitosan

Handbook of Chitin and Chitosan
Author: Sabu Thomas,Anitha Pius,Sreerag Gopi
Publsiher: Elsevier
Total Pages: 858
Release: 2020-07-22
ISBN 10: 0128179678
ISBN 13: 9780128179673
Language: EN, FR, DE, ES & NL

Handbook of Chitin and Chitosan Book Review:

The Handbook of Chitin and Chitosan: Chitin and Chitosan Based Polymer Materials for Various Applications, Volume Three, is a must-read for polymer chemists, physicists and engineers interested in the development of ecofriendly micro and nanostructured functional materials based on chitin and their various applications. The book addresses their isolation, preparation and properties and their composites, nanomaterials, manufacturing and characterizations. This is the third of three volumes in a series that contains the latest on the major applications of chitin and chitosan based IPN’s, blends, gels, composites and nanocomposites, including environmental remediation, biomedical applications and smart material applications. Provides a comprehensive overview of Chitin and Chitosan materials, from their synthesis and nanomaterials, to their manufacture and applications Volume Three focuses on the applications of Chitin and Chitosan Includes contributions from leading researchers across the globe and from industry, academia, government and private research institutions Highlights current status and future opportunities

Chitin and Chitosan Properties and Applications

Chitin and Chitosan  Properties and Applications
Author: Lambertus A. M. van den Broek,Carmen G. Boeriu,Christian V. Stevens
Publsiher: John Wiley & Sons
Total Pages: 536
Release: 2020-01-28
ISBN 10: 1119450438
ISBN 13: 9781119450436
Language: EN, FR, DE, ES & NL

Chitin and Chitosan Properties and Applications Book Review:

Offers a comprehensive guide to the isolation, properties and applications of chitin and chitosan Chitin and Chitosan: Properties and Applications presents a comprehensive review of the isolation, properties and applications of chitin and chitosan. These promising biomaterials have the potential to be broadly applied and there is a growing market for these biopolymers in areas such as medical and pharmaceutical, packaging, agricultural, textile, cosmetics, nanoparticles and more. The authors – noted experts in the field – explore the isolation, characterization and the physical and chemical properties of chitin and chitosan. They also examine their properties such as hydrogels, immunomodulation and biotechnology, antimicrobial activity and chemical enzymatic modifications. The book offers an analysis of the myriad medical and pharmaceutical applications as well as a review of applications in other areas. In addition, the authors discuss regulations, markets and perspectives for the use of chitin and chitosan. This important book: Offers a thorough review of the isolation, properties and applications of chitin and chitosan. Contains information on the wide-ranging applications and growing market demand for chitin and chitosan Includes a discussion of current regulations and the outlook for the future Written for Researchers in academia and industry who are working in the fields of chitin and chitosan, Chitin and Chitosan: Properties and Applications offers a review of these promising biomaterials that have great potential due to their material properties and biological functionalities.

Fungal Nanobionics Principles and Applications

Fungal Nanobionics  Principles and Applications
Author: Ram Prasad,Vivek Kumar,Manoj Kumar,Shanquan Wang
Publsiher: Springer
Total Pages: 316
Release: 2018-07-27
ISBN 10: 9811086664
ISBN 13: 9789811086663
Language: EN, FR, DE, ES & NL

Fungal Nanobionics Principles and Applications Book Review:

Fungal nanobionics has great prospects for developing new products with industrial, agriculture, medicine and consumer applications in a wide range of sectors. The fields of chemical engineering, agri-food, biochemical, pharmaceuticals, diagnostics and medical device development all employ fungal products, with fungal nanomaterials currently used in a wide range of applications, ranging from drug development to food industry and agricultural sector. The fungal agents emerge as an environmentally friendly, clean, non‐toxic agent for the biogenic metal nanoparticles and employs both intracellular and extracellular methods. The simplicity of scaling up and downstream processing and the presence of fungal mycelia affording an increased surface area provide key advantages. In addition, the larger spectrum of synthesized nanoparticle morphologies and the substantially faster biosynthesis rate in cell-free filtrate (due to the higher amount of proteins secreted in fungi) make this a particularly enticing route. Understanding the diversity of fungi in assorted ecosystems, as well as their interactions with other microorganisms, animals and plants, is essential to underpin real and innovative technological developments and the applications of metal nanoparticles in many disciplines including agriculture, catalysis, and biomedical biosensors. Importantly, biogenic fungal nanoparticles show significant synergistic characteristics when combined with antibiotics and fungicides to offer substantially greater resistance to microbial growth and applications in nanomedicine ranging from topical ointments and bandages for wound healing to coated stents.

Sustainable Agriculture Reviews 35

Sustainable Agriculture Reviews 35
Author: Grégorio Crini,Eric Lichtfouse
Publsiher: Springer
Total Pages: 338
Release: 2019-06-04
ISBN 10: 3030165388
ISBN 13: 9783030165383
Language: EN, FR, DE, ES & NL

Sustainable Agriculture Reviews 35 Book Review:

This book reviews recent research and applications of chitin and chitosan, as natural alternatives of fossil fuel products, in green chemistry, energy, biotechnology, bioprinting, medicine, water treatment, agriculture and food science. Chitin and chitosan products are polysaccharides derived from food waste of crustaceans and fungi, and thus are cheap, abundant, sustainable, non-toxic, recyclable and biocompatible.

Chitin and Chitosan Derivatives

Chitin and Chitosan Derivatives
Author: Se-Kwon Kim
Publsiher: CRC Press
Total Pages: 527
Release: 2013-12-04
ISBN 10: 1466566280
ISBN 13: 9781466566286
Language: EN, FR, DE, ES & NL

Chitin and Chitosan Derivatives Book Review:

A natural long-chain polymer, chitin is the main component of the cell walls of fungi, the exoskeletons of arthropods (including crustaceans and insects), the radulas of mollusks, and the beaks and internal shells of cephalopods. However, marine crustacean shells are the primary sources of the chitin derivative chitosan. Chitin and chitosan are useful for various biological and biomedical applications, although they have been limited by poor solubility in the past. Current research focuses on increasing their solubility and bioactivity through molecular modifications. The resulting derivatives are receiving much attention for interesting properties, such as biocompatibility, biodegradability, and nontoxicity, that make them suitable for use in the biomedical field. Chitin and Chitosan Derivatives: Advances in Drug Discovery and Developments presents current research trends in the synthesis of chitin and chitosan derivatives, their biological activities, and their biomedical applications. Part I discusses basic information about the synthesis and characterization of a variety of derivatives, including the preparation of chitin nanofibers. Part II covers chitin and chitosan modifications as the basis for biological applications. It describes antioxidant, anti-inflammatory, anticancer, antiviral, anticoagulant, and antimicrobial activities. Part III addresses chemically modified and composite materials of chitin and chitosan derivatives for biomedical applications, such as tissue engineering, nanomedicine, drug delivery, and wound dressing. A must-have reference for novices and experts in biotechnology, natural products, materials science, nutraceuticals, and biomedical engineering, this book presents a wide range of biological and biomedical applications of chitin and chitosan derivatives for drug discovery and development.

Natural Polysaccharides in Drug Delivery and Biomedical Applications

Natural Polysaccharides in Drug Delivery and Biomedical Applications
Author: Md Saquib Hasnain,Amit Kumar Nayak
Publsiher: Academic Press
Total Pages: 654
Release: 2019-07-23
ISBN 10: 0128170565
ISBN 13: 9780128170564
Language: EN, FR, DE, ES & NL

Natural Polysaccharides in Drug Delivery and Biomedical Applications Book Review:

Natural Polysaccharides in Drug Delivery and Biomedical Applications provides a fundamental overview of natural polysaccharides, their sources, extraction methodologies, and characterizations. It covers specific natural polysaccharides and their effective application in drug delivery and biomedical use. Additionally, chapters in the book discuss key topics including the sources and extraction methodologies of natural polysaccharides, their role in tissue engineering applications, polysaccharide-based nanoparticles in biomedical applications, and their role in the delivery of anticancer drugs. Written by industry leaders and edited by experts, this book emphasizes recent advances made in the field. Natural Polysaccharides in Drug Delivery and Biomedical Applications provides academics, researchers, and pharmaceutical health care professionals with a comprehensive book on polysaccharides in pharmaceutical delivery process. Provides fundamental concepts of natural polysaccharides as it applies to the pharmaceutical, biomedical, and biotechnology industries Includes contributions from global leaders and experts from academia, industry, and regulatory agencies in the application of natural polysaccharides in pharmaceutical products and biomedical utilization Offers practical examples, illustrations, chemical structures, and research case studies to help explain natural polysaccharides concepts in drug delivery and biomedical applications

Chitin Chitosan Oligosaccharides and Their Derivatives

Chitin  Chitosan  Oligosaccharides and Their Derivatives
Author: Se-Kwon Kim
Publsiher: CRC Press
Total Pages: 666
Release: 2010-07-14
ISBN 10: 1439816042
ISBN 13: 9781439816042
Language: EN, FR, DE, ES & NL

Chitin Chitosan Oligosaccharides and Their Derivatives Book Review:

Biopolymers found in marine animals and plants offer tremendous, largely untapped pharmaceutical potential. Research shows that these biopolymers can be used to combat various infectious as well as inflammatory, oxidative, and carcinogenic factors. Chitin, Chitosan, Oligosaccharides and Their Derivatives: Biological Activities and Applications cove

Chitosan Based Hydrogels

Chitosan Based Hydrogels
Author: Kangde Yao,Junjie Li,Fanglian Yao,Yuji Yin
Publsiher: CRC Press
Total Pages: 521
Release: 2016-04-19
ISBN 10: 1439821151
ISBN 13: 9781439821152
Language: EN, FR, DE, ES & NL

Chitosan Based Hydrogels Book Review:

Due to their unique properties, chitosan-based materials have emerged as useful resources in a variety of medicines, drug controlled-release carriers, tissue engineering scaffolds, and immobilized enzymes. But many of these materials have yet to reach the commercial market. Therefore, more work must be completed to fill the gap between research and production. Exploring the state of the field, Chitosan-Based Hydrogels: Functions and Applications details the latest progress in the research and development of chitosan-based biomaterials. The book introduces the formation and chemical structure of chitosan-based hydrogels. It also discusses the relationship between their structure and functions, which provides a theoretical basis for the design of biomaterials. In addition, many real-world examples illustrate the potential application of chitosan-based hydrogels in various areas, including materials science, biotechnology, pharmaceuticals, regenerative medicine, and cell engineering. By examining the structure and functions of chitosan-based hydrogels in living systems, this book provides the foundation for future research. It encourages readers to contribute to further research and development of these unique biomaterials.

Extracellular Sugar Based Biopolymers Matrices

Extracellular Sugar Based Biopolymers Matrices
Author: Ephraim Cohen,Hans Merzendorfer
Publsiher: Springer
Total Pages: 820
Release: 2019-07-02
ISBN 10: 3030129195
ISBN 13: 9783030129194
Language: EN, FR, DE, ES & NL

Extracellular Sugar Based Biopolymers Matrices Book Review:

The extracellular matrix (ECM) is an acellular three-dimensional network composed of proteins, glycoproteins, proteoglycans and exopolysaccharides. It primarily serves as a structural component in the tissues and organs of plants and animals, or forms biofilms in which bacterial cells are embedded. ECMs are highly dynamic structures that undergo continuous remodeling, and disruptions are frequently the result of pathological processes associated with severe diseases such as arteriosclerosis, neurodegenerative illness or cancer. In turn, bacterial biofilms are a source of concern for human health, as they are associated with resistance to antibiotics. Although exopolysaccharides are crucial for ECM formation and function, they have received considerably little attention to date. The respective chapters of this book comprehensively address such issues, and provide reviews on the structural, biochemical, molecular and biophysical properties of exopolysaccharides. These components are abundantly produced by virtually all taxa including bacteria, algae, plants, fungi, invertebrates and vertebrates. They include long unbranched homopolymers (cellulose, chitin/chitosan), linear copolymers (alginate, agarose), peptoglycans such as murein, heteropolymers like a variety of glycosaminoglycans (hyaluronan, dermatan, keratin, heparin, Pel), and branched heteropolymers such as pectin and hemicellulose. A separate chapter is dedicated to modern industrial and biomedical applications of exopolysaccharides and polysaccharide-based biocomposites. Their unique chemical, physical and mechanical properties have attracted considerable interest, inspired basic and applied research, and have already been harnessed to form structural biocomposite hybrids for tailor-made applications in regenerative medicine, bioengineering and biosensor design. Given its scope, this book provides a substantial source of basic and applied information for a wide range of scientists, as well as valuable textbook for graduate and advanced undergraduate students.

Applications of Chitan and Chitosan

Applications of Chitan and Chitosan
Author: Mattheus F. A. Goosen
Publsiher: CRC Press
Total Pages: 329
Release: 2020-08-19
ISBN 10: 100015436X
ISBN 13: 9781000154368
Language: EN, FR, DE, ES & NL

Applications of Chitan and Chitosan Book Review:

The main driving force behind the development of new applications for chitin and its derivative chitosan lies with the fact that these polysaccharides represent a renewable source of natural biodegradable polymers. Since chitin is the second most abundant natural polymer, academic as well as industrial scientists are faced with a great challenge to find new and practical applications for this material. This book provides an examination of the state of the art, and discusses new applications as well as potential products. Applications of Chitin and Chitosan deals almost exclusively with applications. Previous books in the field have devoted less than 30% of their material to commercial or medical uses. In the past thirty years, substantial progress has been made on fundamental and applied research in chitosan technology. One of the driving forces behind this rapid development has been the decrease in the supply of natural resources. At the same time there has been an increased realization that there are abundant alternative bioresources. Two factors-economics and versatility-have also stimulated interest in chitosan's utilization in various fields. Chitin and chitosan derivatives have applications in fields that range from fertilizers to pharmaceuticals. Chitosan is no longer just a waste by-product from the seafood processing industry. This material is now being utilized by industry to solve problems and to improve existing products, as well as to create new ones. Applications of Chitin and Chitosan is illustrated with over 100 photos, charts, graphs and figures and more than 40 tables. Applications of Chitin and Chitosan will be of interest to industrial personnel involved in bioprocessing as well as bioengineering students, specialists in the biomedical and biopharmaceutical industry, biochemists, food engineers, environmentalists, and microbiologists and biologists who specialize in chitosan technology. Publication: Fall 1996.

Advances in Chitin Chitosan Characterization and Applications

Advances in Chitin Chitosan Characterization and Applications
Author: Marguerite Rinaudo,Francisco M. Goycoolea
Publsiher: MDPI
Total Pages: 414
Release: 2019-04-23
ISBN 10: 3038978027
ISBN 13: 9783038978022
Language: EN, FR, DE, ES & NL

Advances in Chitin Chitosan Characterization and Applications Book Review:

Functional advanced biopolymers have received far less attention than renewable biomass (cellulose, rubber, etc.) used for energy production. Among the most advanced biopolymers known is chitosan. The term chitosan refers to a family of polysaccharides obtained by partial de-N-acetylation from chitin, one of the most abundant renewable resources in the biosphere. Chitosan has been firmly established as having unique material properties as well as biological activities. Either in its native form or as a chemical derivative, chitosan is amenable to being processed—typically under mild conditions—into soft materials such as hydrogels, colloidal nanoparticles, or nanofibers. Given its multiple biological properties, including biodegradability, antimicrobial effects, gene transfectability, and metal adsorption—to name but a few—chitosan is regarded as a widely versatile building block in various sectors (e.g., agriculture, food, cosmetics, pharmacy) and for various applications (medical devices, metal adsorption, catalysis, etc.). This Special Issue presents an updated account addressing some of the major applications, including also chemical and enzymatic modifications of oligos and polymers. A better understanding of the properties that underpin the use of chitin and chitosan in different fields is key for boosting their more extensive industrial utilization, as well as to aid regulatory agencies in establishing specifications, guidelines, and standards for the different types of products and applications.

Chitin and Chitosan for Regenerative Medicine

Chitin and Chitosan for Regenerative Medicine
Author: Pradip Kumar Dutta
Publsiher: Springer
Total Pages: 389
Release: 2015-09-04
ISBN 10: 8132225112
ISBN 13: 9788132225119
Language: EN, FR, DE, ES & NL

Chitin and Chitosan for Regenerative Medicine Book Review:

The book is an excellent reference for scientists, researchers and students working in the field of areas of biopolymeric biomaterials, biomedical engineering, therapeutics, tissue engineering and regenerative medicine. The book is divided into two parts: Part I will focus on the tissue engineering and Part II focuses on therapeutics, functionalization and computer-aided techniques. The book consists of 13 chapters contributed by 20 international contributors who are leading experts in the field of biopolymers and its applications. It will focus on the advancements of chitin and chitosan in regenerative medicine. Regenerative medicine in tissue engineering is the process of replacing or regenerating human cells, tissues, or organs to restore or establish normal function. It is an incredibly progressive field of medicine that may, in the near future, help with the shortage of life-saving organs available through donation for transplantation vis-a-vis regenerative medicine focuses on therapeutics, functionalization and computer-aided techniques. It also covers physical and chemical aspects of chitin and chitosan, structural modifications for biomedical applications, chitosan based scaffolds and biomodelling in tissue engineering, nanomedicines and therapeutic applications. With the broad range of applications, the world is waiting for biopolymers to serve as the basis for regenerative medicine and biomedical applications.

Chitin

Chitin
Author: Eugene Khor
Publsiher: Elsevier
Total Pages: 154
Release: 2014-06-12
ISBN 10: 0080999409
ISBN 13: 9780080999401
Language: EN, FR, DE, ES & NL

Chitin Book Review:

The second edition of Chitin underscores the important factors for standardizing chitin processing and characterization. It captures the essential interplay between chitin's assets and limitations as a biomaterial, placing the past promises of chitin in perspective, addressing its present realities and offering insight into what is required to realize chitin's destiny (including its derivative, chitosan) as a biomaterial of the twenty-first century. This book is an ideal guide for both industrialists and researchers with a vested interest in commercializing chitin. An update on the research since 2001 as it pertains to the biomaterials and biomedical applications of chitin and chitosan An expanded discussion on positioning chitin and chitosan for biomedical applications Presents regulatory aspects of chitin and chitosan