Bandyopadhyay / Bose Characterization of Biomaterials

1. Auflage 2013
ISBN: 978-0-12-415863-4
Verlag: Elsevier Science & Techn.
Format: EPUB
Kopierschutz: 6 - ePub Watermark

E-Book, Englisch, 450 Seiten

One of the key challenges current biomaterials researchers face is identifying which of the dizzying number of highly specialized characterization tools can be gainfully applied to different materials and biomedical devices. Since this diverse marketplace of tools and techniques can be used for numerous applications, choosing the proper characterization tool is highly important, saving both time and resources.Characterization of Biomaterials is a detailed and multidisciplinary discussion of the physical, chemical, mechanical, surface, in vitro and in vivo characterization tools and techniques of increasing importance to fundamental biomaterials research.Characterization of Biomaterials will serve as a comprehensive resource for biomaterials researchers requiring detailed information on physical, chemical, mechanical, surface, and in vitro or in vivo characterization. The book is designed for materials scientists, bioengineers, biologists, clinicians and biomedical device researchers seeking input on planning on how to test their novel materials, structures or biomedical devices to a specific application. Chapters are developed considering the need for industrial researchers as well as academics. - Biomaterials researchers come from a wide variety of disciplines: this book will help them to analyze their materials and devices taking advantage of the multiple experiences on offer - Coverage encompasses a cross-section of the physical sciences, biological sciences, engineering and applied sciences characterization community, providing gainful and cross-cutting insight into this highly multi-disciplinary field - Detailed coverage of important test protocols presents specific examples and standards for applied characterization

Autoren/Hrsg.

Bandyopadhyay, Amit

Bose, Susmita

Leseproben

Chapter 1 Introduction to Biomaterials Susmita Bose and Amit Bandyopadhyay, W. M. Keck Biomedical Materials Research Lab, School of Mechanical and Materials Engineering, Washington State University, Pullman, WA, USA Chapter Outline 1.1. Introduction 1.2. Types of Materials 1.3. Biomaterials and Biocompatibility 1.4. Types of Biomaterials 1.5. Properties of Biomaterials 1.6. Biomaterials Characterization and Outline of this Book 1.7. Summary Suggested Further Reading 1.1 Introduction
With the evolution of human civilization, the field of biomaterials evolved involving different materials at multiple length scales from nano- to micro- to macrolevel with a simple focus to extend human life and improve the quality of life. Over 1000 years back, silver in different forms was used as an antimicrobial agent to prevent infection. Different types of surgical procedures can also be found during early stages of civilization. However, probably the most significant developments took place in the field of biomaterials over the years 1901–2000. Artificial joints improved the quality of life for millions of people over the past 60 years, resorbable sutures simplified surgical procedures, and different cardiovascular devices saved millions of lives, just to name a few. The advent of tissue engineering and organ regeneration is pushing the frontiers of science today to make the years 2001–2100 more exciting in the field of biomaterials. However, to appreciate the benefits, it is not just the design of biomaterials that is important, but sound engineering design and appropriate materials and device characterization are also needed. Moreover, for a biomedical device to see the commercialization light, it is also important to carry out testing following appropriate standards to get regulatory approval. Overall, benefits of biomaterials research can only be appreciated when these materials are characterized well at both the materials level and the device level following regulatory guidelines. Considering the multidisciplinary nature of the field, it is also not easy to carry out large variety of experiments using different techniques. Realizing this problem in biomaterials characterization, we have developed this book to offer an insight on various characterization tools focusing on biomaterials and biomedical devices. 1.2 Types of Materials
Materials can be classified into different groups based on their crystal structure, bonding, and macrostructures. Each subgroup of materials shows somewhat similar properties and then those materials can be clubbed together to study their performance for different applications. If we look at types of bonding, materials can be classified into three broad categories—metals, ceramics and polymers. Materials that are bonded via metallic bonds are called metals. Due to abundance of free electrons in metallic bonds, metals are both thermally and electrically conductive, and show malleability in terms of their mechanical properties. Materials that are primarily ionic and/or covalently bonded are called ceramics. Since ionic and covalent bonds do not offer any free electrons, ceramics are generally nonconducting materials both thermally and electrically. However, due to the movements of defects, some ceramics show conductivity at higher temperature. Materials that are based on long carbon chain and covalently bonded with some secondary bonding are polymers, where “mers” or units are connected in the long range. Due to covalent bonding, most polymers are nonconducting. When any three of these main materials are mixed together without losing its inherent characteristics, then we form a new class of materials, called composites. Some examples of natural composites are wood and bone. When we look at the unit cell, the basic building block of any material, we can classify materials into three groups—crystalline, semicrystalline and amorphous. If the unit cell is repeated in all three directions and maintains a long-range order, then those materials are called a crystalline material such as iron, titanium, chromium or polycrystalline ceramics. The basic unit cell, defined by the three-dimensional shape and atom positions, can be for example body centered cubic or face centered cubic or hexagonal close packed (hcp), where “cubic” or “hexagonal” are crystal systems defined by the shape of the unit cell and “body centered” or “face centered” are specific atom positions that defines the Bravais lattice of the unit cell. These kinds of simple structures are common for most metallic systems, which are mainly crystalline in nature. For many materials, unit cell does not repeat itself in three dimension for long range, but only shows short-range repetition. Those materials with short-range ordering of unit cells are called amorphous materials or glass. Due to lack of ordering, glassy materials show unique properties such as glass transition temperature (Tg), where a liquid phase transforms to a solid rubbery phase. There are also a group of materials that are partially glassy and partially crystalline. Those materials are called semicrystalline materials. Among others, many polymeric materials show semicrystalline nature. Materials can also be classified as natural or synthetic. Natural materials are those which are available in nature such as wood, rocks, corals and bones. Most natural materials are ceramics, polymers and their composites. Mother Nature designed these materials for a variety of purposes such as sensors, reservoirs, structural support or energy converters. Most of these materials have complex chemistry and structure and the mankind is still exploring those to enrich their learning. Synthetic materials are man-made materials designed for specific functionality. These materials include metallic materials such as steels for fracture management devices, to titanium and its alloys for implant, to polymers for ocular lenses and to ceramics for bone-tissue engineering. Synthetic materials are tailored for specific chemistry and structure for properties that can be utilized to improve our everyday life. Once processed, their physical, chemical, mechanical and sometimes biological property determination is necessary based on application need. Materials can also be classified based on their macrostructures such as dense or porous. Most natural materials such as rocks, tissues, wood are porous materials. Porosity in these materials can serve various purposes. Most ceramic materials have residual porosity. Porosity can be nonuniform and vary in size and distribution. Porosity in materials can vary from 1% to 10% such as in cortical bone to as high as >70% in some cancellous bones. Because of porosity, these materials are lighter weight, and many times show nonuniform properties at different directions. However, it is very difficult to mimic such natural materials in terms of composition, structure and properties. When materials do not show any porosity, those are called dense materials. Most metallic materials are dense in nature with residual porosity <1%. Dense materials are typically isotropic in nature and can be shaped easily by various forming techniques. Figure 1.1 schematically shows different types of materials. Any one material can also fall into many of these categories. For example, bone is a natural material, that is porous, and a ceramic–polymer composite. FIGURE 1.1 Different types of materials. 1.3 Biomaterials and Biocompatibility
A biomaterial is a material, synthetic or natural, that can be used in medical applications to perform a body function or replace a body part or tissue. A biomaterial is intended to interact at the interface of biological systems. It may also be used as a delivery system for drug or biological factor. Biomaterials are designed based on application needs. Reaching back to the beginnings of civilization, the Romans, Aztecs and Chinese used gold in dental applications. The Mayans were found to have fashioned dental implants out of sea shells with results indicating actual bone integration. A biomaterial must be biocompatible, i.e., it should be friendly to biological system and not do any harm to the system, whether at the cellular level or at the system level. A biocompatible material should elicit appropriate host response or able to perform its intended function in a specific application without the presence of adverse reactions. This is an emerging paradigm that requires and pushes unique multidisciplinary boundaries based on understanding and integration of concepts from various broad fields, but not limited to, chemistry, biology, materials science, mechanical, chemical and electrical engineering as well as medicine. Biomaterials are used to augment, repair or replace any tissue, organ, or function of the body that has been lost through trauma, disease or injury. Recent practice in medicine often times uses tissue reconstruction using autograft, where tissue graft or organ transplant from one point to another of the same individual takes place. However, limited availability, donor site morbidity and above all, the need for a second surgery restrict their application. On the other hand, potential alternative is the use of allograft, i.e. tissue graft or organ transplant from a donor of the same species as the recipient. The other...