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Biomaterials: A Systems Approach to Engineering Concepts
Many believe that it is impossible to write a book relating to materials used in medicine. There are several reasons for this dilemma. Books that emphasize the materials’ concepts are founded on volumetric replacement and biological response and less on a mechanical or other analysis of the design environment. The gap is even larger when considering organ function that will require materials integration. Other monographs that are focused on tissue engineering are also hard to gauge, because there is so much detail needed to define a scaffold structure, optimize the culturing environment, identify an implantation protocol, test in appropriate animal models, to establish when and how to assay, and to confirm a successful outcome. It is simply a grand challenge to settle on an optimum strategy to address a specific disease and that could be why tissue engineering has been so much the realm of vibrant research but not as many commercial products. Also depending on the cell source, one may need to consider long-term immune suppression to reduce the risk of host/graft attack. It is simply hard to compare the promise of a tissue engineered solution with stopgap measures being implemented and optimized as current practice, even if an organic cellular solution is preferred. It is also harder to value new engineering approaches since the marketplace prevents one from disclosing a complete story, lest they give away a competitive corporate advantage. The clinical books are also focused more closely on the aspects of biocompatibility and the subtleties associated with materials, compositional variations, or/and end mechanical function are sometimes lacking. These comments are made not to criticize the discipline but more to establish the landscape. Many of them are excellent sources of information and I have cited them here.
There are many summaries of content in biomaterials that can satisfy the instructor and students of this discipline. For those who desire a textbook option, the choices coincide with what one is more comfortable supplementing. There are monographs and compendia in which often some of the most noted researchers are recruited to offer perspective on their area of expertise. These monographs are often quite deep, but for a senior/graduate class, foundation level materials to support what research reviews are about can be incomplete, and the links between one research topic and another require that all authors are aware of what the other authors are contributing. As a result there are often few examples or problems to consider more deeply.
There are several recent contributions to the discipline in biomaterials that do a more comprehensive job of satisfying the goal of establishing learning objectives in what look more like conventional textbooks. They all have their merits and it is encouraging to see the discipline taking such a wide variance on several conventional textbooks. I applaud the authors of new textbooks in the last several years, as I know that the original ideas go back a long time and it is not an easy process to complete anything like this. I remained committed to my own ideas that were likely formed during the same interval in which these other books have been produced. It is encouraging to see that, for example, there is more attention being placed on nanoparticles as part of enhanced diagnostics and phase contrast fluids; the commitment to include new and distinct areas of biomaterials offers both a distinct pivot in the engineering element of biomaterials and makes teaching biomaterials less of a history lesson.
The book is organized into 15 chapters and is structured as a cumulative presentation with three main themes, but with an understanding that the clinical relevance is distributed where it is sensible to do. The first section ( Chapter 1: Cell Biology, Chapter 2: Cell Expression: Proteins and Their Characterization, Chapter 3: Bones and Mineralized Tissues, Chapter 4: Soft Tissues, Chapter 5: Property Assessments of Tissues, and Chapter 6: Environmental Effects on Natural Tissues) assumes that there is some basic understanding of biochemistry focusing not on the nuances of cell physiology, but more on the outcomes that arise in terms of cell expression, protein structure, and attributes to characterize both cells and proteins. These differences are used to justify the need to analyze normal and diseased tissues and fluid extractions focusing on diagnostics and gauging cell and tissue health adjacent to biomaterial installations. It is important to understand that structural proteins such as collagen keratin and silk have different sequences and forms (collagen has many different forms actually), and these are organizationally different than regulatory proteins (immunoglobulins), hormonal proteins (insulin and glucagon), and contractile proteins (actin and myosin) expressed in muscular tissues.
It is also worth noting that subsets of people can have different connective tissue structures, as noted in Chapter 3, Bones and Mineralized Tissues, and Chapter 4, Soft Tissues. It is known, for example, that people with Ehlers Danlos syndrome have hyperelastic skin (statistically different than the normal population) that makes them more flexible, but also at larger risk for aortic dissection and other cardiovascular abnormalities. Within bioengineering, we never explicitly discuss how subsets of people with a different collagen makeup have different clinical outcomes nor are we aware of its specific function for traces of other minute forms of collagen which might serve some crucial role in development. It is appropriate to at least sensitize engineers and scientists that a deeper understanding is needed considering proteins as tissue in the long run. There might be hundreds of similar examples each instructor could give to students and these are simply ice breakers to make students think whether it be for hard or soft tissues.
Chapter 6, Environmental Effects on Natural Tissues, is a perfect example of how a systems approach can be taken to understand disease progression in aging, chronic conditions, and diseases that remain frustratingly insoluble even now. By understanding the disease progression from a systems perspective, there is a chance to understand how to value organic, synthetic, and clinical efforts to manage disease. It can provide some insight why breast tissue self-examinations are a powerful first gauge in understanding the biophysical changes in tumorous tissues among others.
The second section ( Chapter 7, Metallic Biomaterials, Chapter 8, Ceramic Biomaterials, Chapter 9, Polymeric Biomaterials, and Chapter 10, Nanomaterials and Phase Contrast Imaging Agents) presents the composition, structure, and performance characteristics of materials commonly accepted and used as biomaterials. Presented here is the engineering content to analyze the structure of these materials, how physical, electrical, and optical properties are measured, how these metals, ceramics, and polymers are produced, how phase determinations are performed, and pointing to opportunities to new materials development. For example:
- how are properties determined (mechanical behavior, yielding, etc.),
- how is it that structure is measured (X-ray diffraction and scattering, microscopy, etc.).
For that matter, dynamic issues such as how are changes in tissue structure (bone density, cataracts) arise in aging of natural tissues; how corrosion, amalgamation, and other chemical reactions that occur in vivo evolve; and how are these measured should be included. The scale of materials from nano to meso can be presented, showing examples where nanoscale matters (phase contrast fluids, drug delivery vehicles, diffusional barriers, etc.). Key science and mathematical content can support the quantitative elements of the course here (modulus and yield point determinations, Braggs Law, Snell’s law, calorimetry, gravimetric determinations, etc.).
The final section ( Chapters 11: Orthopedics, Chapter 12: Neural Interventions, Chapter 13: Cardiovascular Interventions: The Alliteration of P’s Relating to Medicine. Proper Perfusion Prevents Pervasive Procedures Proffered to Improve Cardiovascular Health, Chapter 14: Artificial Organs, and Chapter 15: Special Topics: Assays Applied to Both Health and Sports) is a medical subdiscipline by subdiscipline area assessment that helps to define current issues being experienced by clinics now and for the immediate future. The main takeaway and the major crux of this book are focused on the fact that while tissue engineering might be the long-term future for medical engineering professionals and clinicians, graduating engineers and incoming medical professionals need to be much more aware of the current state of the art in a range of disciplines using materials as replacement tissues, organs, and repairs. Again, this book is more about the value of competitive technological interventions and clinical procedures that are used today and likely to be further optimized. This book is an empowering treatise that gives credit to how clinicians can design their own solutions based on their own problem solving skills. As an example, tissue engineering could be used to produce heart valves to fix compromised valves that are calcified but clinicians and medical engineers and scientists need to understand how clinicians fix defective valves today through their deployment of sutures, threads, annuloplasty rings, and scalpels. The theme is that graduating engineers who are taught a more objective view of the field of medical intervention need to have a stronger understanding of how medicine is practiced now in the clinic on their terms and using their language.
- Provides a fully comprehensive treatment relating to the construction and use of materials in medicine
- Presents perspectives of disease states to encourage the design of materials and systems targeted at specific conditions
- Defines current issues experienced by clinics to enable optimized engineering solutions
The highly interdisciplinary field of materials science examines elements of applied physics and chemistry, as well as chemical, mechanical, civil, and electrical engineering. Nanoscience and nanotechnology in particular have yielded major innovations in this area, such as graphene and carbon nanotubes. Elsevier’s authoritative content in this area ranges from undergraduate textbooks to multi-volume reference works investigating the relationships between the structure of materials and their properties. Our journals (including Materials Today), books, and eBooks help researchers stay abreast of developments in this swiftly advancing field, coving major sub-disciplines like energy and power; metals and alloys; ceramics; composite materials; polymer science and biomaterials; interdisciplinary materials science; and structural materials.