Natural and Synthetic Biomedical Polymers

Sangamesh G. Kum bar, Cato Laurencin, Meng Deng

• Publisher: Elsevier Science
• Year: 2014
• ISBN:
  9780123972903
• Topic: Technologie et ingénierie
• Subtopic: Science des matériaux

Polymers are important and attractive biomaterials for researchers and clinical applications due to the ease of tailoring their chemical, physical and biological properties for target devices. Due to this versatility they are rapidly replacing other classes of biomaterials such as ceramics or metals. As a result, the demand for biomedical polymers has grown exponentially and supports a diverse and highly monetized research community. Currently worth $1.2bn in 2009 (up from $650m in 2000), biomedical polymers are expected to achieve a CAGR of 9.8% until 2015, supporting a current research community of approximately 28, 000+.

Summarizing the main advances in biopolymer development of the last decades, this work systematically covers both the physical science and biomedical engineering of the multidisciplinary field. Coverage extends across synthesis, characterization, design consideration and biomedical applications. The work supports scientists researching the formulation of novel polymers with desirable physical, chemical, biological, biomechanical and degradation properties for specific targeted biomedical applications.

• Combines chemistry, biology and engineering for expert and appropriate integration of design and engineering of polymeric biomaterials
• Physical, chemical, biological, biomechanical and degradation properties alongside currently deployed clinical applications of specific biomaterials aids use as single source reference on field.
• 15+ case studies provides in-depth analysis of currently used polymeric biomaterials, aiding design considerations for the future

Chapter 1

Polymer Synthesis and Processing

Mahadevappa Y. Kariduraganavar *; Arjumand A. Kittur ^†; Ravindra R. Kamble * ^* Department of Studies in Chemistry, Karnatak University, Dharwad, India
^† Department of Chemistry, SDM College of Engineering & Technology, Dharwad, India

Abstract

Polymer scientists have made an extensive research in the development of biodegradable polymers, which could find enormous applications in the area of medical science. Today, various biopolymers have been prepared and utilized in different biomedical applications. Despite the apparent proliferation of biopolymers in medical science, the science and technology of biopolymers is still in its early stages of development. Tremendous opportunities exist and will continue to exist for the penetration of biopolymers in every facet of medical science through intensive research and development. Therefore, this chapter addresses different polymerization methods and techniques employed for the preparation of biopolymers. The emphasis is on the general properties of biopolymers, synthetic protocols, and their biomedical applications. In order to make the useful biomedical devices from the polymers to meet the demands of medical science, various processing techniques employed for the development of devices have been discussed. Further, perspectives in this field have been highlighted and conclusions arrived at. The relevant literature was collected from different sources, including Google sites, books, and reviews.

Keywords

Biopolymers

Polymerization techniques

Polymer extraction

Biomedical applications

Polymer processing

Chapter Outline

1.1 Introduction

1.2 Types of Polymerization

1.2.1 Addition Polymerization

1.2.2 Condensation Polymerization

1.2.3 Metathesis Polymerization

1.3 Techniques of Polymerization

1.3.1 Solution Polymerization

1.3.2 Bulk (Mass) Polymerization

1.3.3 Suspension Polymerization

1.3.4 Precipitation Polymerization

1.3.5 Emulsion Polymerization

1.4 Polymers: Properties, Synthesis, and Their Biomedical Applications

1.4.1 Polycaprolactone

1.4.2 Polyethylene Glycol

1.4.3 Polyurethane

1.4.4 Polydioxanone or Poly-p-Dioxanone

1.4.5 Polymethyl Methacrylate

1.4.6 Polyglycolic Acid or Polyglycolide

1.4.7 Polylactic Acid or Polylactide

1.4.8 Polylactic-co-Glycolic Acid

1.4.9 Polyhydroxybutyrate

1.4.10 Polycyanoacrylates

1.4.11 Polyvinylpyrrolidone

1.4.12 Chitosan

1.4.13 Gelatin

1.4.14 Carrageenan

1.4.15 Hyaluronic Acid

1.4.16 Xanthan Gum

1.4.17 Acacia Gum

1.4.18 Alginate

1.5 Processing of Polymers for Biomedical Devices

1.5.1 Fabrication of Polymer Films

1.5.1.1 Solution Casting

1.5.1.2 Melt Pressing

1.5.1.3 Melt Extrusion

1.5.1.4 Bubble Blown Method

1.5.2 Spinning Industrial Polymers

1.5.2.1 Solution Spinning

1.5.3 Fabrication of Shaped Polymer Objects

1.5.3.1 Compression Molding

1.5.3.2 Injection Molding

1.5.3.3 Reaction Injection Molding

1.5.3.4 Blow Molding

1.5.3.5 Extrusion Molding

1.5.4 Calendaring

1.6 Future Perspectives

1.7 Conclusions

Acknowledgments

The authors wish to thank the UGC, New Delhi, for providing the financial support under UPE-FAR-I program (Contract No. 14-3/2012 [NS/PE]). The authors are grateful to the Department of Tool Design, NTTF, Dharwad, for neatly designing the polymer processing illustrations.

1.1 Introduction

Polymers are the most versatile class of biomaterials, being extensively used in biomedical applications such as contact lenses, pharmaceutical vehicles, implantation, artificial organs, tissue engineering, medical devices, prostheses, and dental materials [1–3]. This is all due to the unique properties of polymers that created an entirely new concept when originally proposed as biomaterials. For the first time, a material performing a structural application was designed to be completely resorbed and become weaker over time. This concept was applied for the first time with catgut sutures successfully and, later, with arguable results, on bone fixation, ligament augmentation, plates, and pins [4,5].

Current research on new and improved biodegradable polymers is focused on more sophisticated biomedical applications to solve the patients' problems with higher efficacy and least possible pains. One example is tissue engineering, wherein biodegradable scaffolds seeded with an appropriate cell type provide a substitute for damaged human tissue while the natural process of regeneration is completed [6,7]. Another important application of biodegradable polymer is in the gene therapy that provides a safer way of gene delivery than use of viruses as vectors [8,9].

Recently, an implant prepared from biodegradable polymer played a tremendous beneficial role in replacing the stainless steel implant during the surgery [10]. This has not necessitated a second surgical event for the removal. In addition to this, the biodegradation may offer other advantages. For example, a fractured bone, fixated with a rigid, nonbiodegradable stainless steel implant, has a tendency for refracture upon removal of the implant. The bone does not carry sufficient load during the healing process, since the load is mainly carried by the rigid stainless steel. However, an implant prepared from biodegradable polymer can be engineered to degrade at a rate that will slowly transfer load to the healing bone [11]. Another exciting application for which biodegradable polymers offer tremendous applications is the basis for the drug delivery, either as drug delivery system alone or in conjunction with functioning as a medical device. In orthopedic applications, the delivery of a polymer-bound morphogenic protein may be used to speed up the healing process after a fracture or delivery of an antibiotic may help to prevent osteomyelitis following surgery [12–14]. Biodegradable polymers also make possible targeting of drugs into sites of inflammation or tumors. Prodrugs with macromolecular carriers have also been used for such purposes. The term prodrug has been coined to describe a harmless molecule, which undergoes a reaction inside the body to release the active drug. Polymeric prodrugs are obtained by conjugating biocompatible polymeric molecules with appropriate drugs. Such macromolecular conjugate accumulates positively in tumors, since the permeability of cell membranes of tumor cells is higher than that of normal cells [1,15,16].

Polymers used as biomaterials can be naturally occurring and synthetic or combination of both. Natural polymers are abundant, usually biodegradable, and offer good biocompatibility [11,17]. The biocompatibility of a polymer depends on the specific adsorption of protein to the polymer surface and the subsequent cellular interactions. These interactions with the surrounding medium are governed mostly by the distribution of functional groups on the surface of biomaterial. Several useful biocompatible polymers of microbial origin are being produced from natural sources by fermentation processes. They are nontoxic and truly biodegradable [18]. Biodegradation is usually catalyzed by enzymes and may involve both hydrolysis and oxidation. Aliphatic chains are more flexible than aromatic ones and can easily fit into the active sites of enzymes, and hence, they are easier to biodegrade. Crystallinity hinders polymer degradation. Irregularities in chain morphology prevent crystallization and favor degradat...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright page
• Dedication
• Contributors
• Foreword
• Chapter 1: Polymer Synthesis and Processing
• Chapter 2: Hierarchical Characterization of Biomedical Polymers
• Chapter 3: Proteins and Poly(Amino Acids)
• Chapter 4: Natural Polymers: Polysaccharides and Their Derivatives for Biomedical Applications
• Chapter 5: Chitosan as a Biomaterial: Structure, Properties, and Applications in Tissue Engineering and Drug Delivery
• Chapter 6: Poly(α-ester)s
• Chapter 7: Polyurethanes
• Chapter 8: Poly(Ester Amide)s: Recent Developments on Synthesis and Applications
• Chapter 9: Progress in Functionalized Biodegradable Polyesters
• Chapter 10: Polyanhydrides
• Chapter 11: Polyphosphazenes
• Chapter 12: Pseudo Poly(Amino Acids) Composed of Amino Acids Linked by Nonamide Bonds such as Esters, Imino Carbonates, and Carbonates
• Chapter 13: Polyacetals
• Chapter 14: Biomaterials and Tissue Engineering for Soft Tissue Reconstruction
• Chapter 15: Dendrimers and Its Biomedical Applications
• Chapter 16: Design Strategies and Applications of Citrate-Based Biodegradable Elastomeric Polymers
• Chapter 17: Nucleic Acid Aptamers for Biomaterials Development
• Chapter 18: Biomedical Applications of Nondegradable Polymers
• Chapter 19: Polymeric Biomaterials for Implantable Prostheses
• Chapter 20: Polymeric Materials in Drug Delivery
• Chapter 21: Polymeric Biomaterials in Tissue Engineering and Regenerative Medicine
• Chapter 22: Polymeric Biomaterials for Medical Diagnostics in the Central Nervous System
• Chapter 23: Polymeric Biomaterials in Nanomedicine
• Index