Preface

Surfaces are highly critical in dictating the response of a biomaterial, hence the book, Biosurfaces: A Materials Science and Engineering Perspective is targeted for materials scientists, biomedical engineers, biologists, and design engineers to be able to comprehend the importance of biosurfaces and initiate a dialog between them. More importantly, this book provides a perspective of materials scientist and engineer that will allow parallel communication of materials scientists with biotechnologists, practitioners (dentists, surgeons, etc.) and biomedical professionals alike.

The contribution of understanding the material, being able to design the bulk components, has saturated in recent past, but the idea of engineering the surfaces and using them as potential sites for targeted interaction in vivo has triggered the research and funding in the area of biomaterials and bioengineering. Since primary interaction rests with the surface, appropriate selection (chemistry), design (surface topography and patterning), and performance (both biological and mechanical) are critical in imparting significant upliftment to the current technological applications. This book encompasses the fundaments of materials, the interaction of biomaterials at molecular and cellular levels, surface and biological characterization followed with engineering aspects for practical dental/bone implants and as engineered devices. This book has been conceived in order to motivate the students (especially senior undergraduate and post-graduate) and young researchers alike. In addition, this book will serve as a handbook for experts for easy referral both in academia and in industry.

In this perspective, the present book provides a background and introduces the importance of biomaterials to a reader, who does not have a background on biosurfaces. Furthermore, the book develops the concepts of biomaterials, and provides an insight to the mechanisms and fundaments of designing biosurfaces from an engineering perspective. The book has been structured into various chapters as described in the following sections.

In Chapter 1 on Introduction to Biomaterials, starting with the evolving definition of biomaterial, the content covers the classification of biomaterials. Although a complex interconnection of bioinertness to bioactivity is covered in later chapters, this chapter focuses on the class of polymeric, metallic, and ceramic materials. This chapter outlines the associated challenges and utility in terms of selection of materials for specific applications.

Chapter 2 focuses on the interaction between biomaterials and the tissue. The role of protein adsorption on inducing cell migration and controlled cell deposition is presented in this chapter. The role of extracellular matrix in supporting the cellular growth, proliferation, and adhesion is portrayed. Later, biologically controlled biomineralization, and its utility in supporting the skeletal system, is depicted in detail in this chapter.

Response to implanted materials initially via activation of the immune system (recognizing antigen as foreign body) followed by humoral and cell-mediated immunity is described in Chapter 3. Activation of lymphoctyes (B-cells) and bone marrow (T-cells) cells differentiating into helper and cytotoxic cells is introduced. In addition, release of cytolytic granules by natural killer cells, which lead to target cell lysis, monocytes and macrophages performing phagocytosis apart from releasing other immune substances such as cytokines, is also described in this chapter. Furthermore, the role of granulocytes, mast cells, dendritic cells and follicular dendritic cells in causing allergic reaction and phagocytosis, generating proteins, activation of T-cells and selective maturation of B cells is also presented. Moreover, in vitro agar diffusion test, direct contact method, elution/extract dilution and MTT assay are presented for quantification of cellular response. Designing an in vivo response and the test strategy and performing the sensitization and irritation tests are also detailed in this chapter.

Surface properties of biomaterials are described in Chapter 4. The phenomena of protein adsorption and cell adhesion in resulting biocompatibility is elicited. Following biomimetics, biodegradation is defined. Methods of surface modification (such as immobilization of molecules, organic films, self-assembly, etc.) are described in order to achieve engineered biosurface.

Chapter 5 provides an insight to Multi-Length Scale Hierarchy in Natural Materials, wherein biomimicking aspects in natural materials are discussed. This chapter includes fascinating aspects of (i) high toughness of human bone, turtle shell and nacre, (ii) high compression strength of wood, (iii) tensile strength of spider silk, (iv) sticking and de-sticking of gecko feet and (v) superhydrophobicity of lotus leaf. Furthermore, a few engineering aspects of making the gecko feet structures and mimicking the lotus leaf superhydrophic structure are discussed.

Chapter 6 starts with the natural surfaces rendering superhydrophobicity, following with the learning from nature and being able to mimic such surfaces. The role of surface chemistry and roughness at multi-length scale makes mimicking of natural structures highly challenging. A new dimension of mechanical aspects of surface is also covered in describing the nature of wetting. A few fabrication techniques are listed that can be used in fabricating artificial superhydrophobic surfaces. In the end, engineering of controlled wettability surface is discussed that might open doors for applications in space, biomedical, automotive and other sectors.

Chapter 7 allows the reader to learn the need for altering the surface and applying a surface coating. Various classes of biosurfaces, namely inert, porous, bioactive and resorbable surfaces, are defined and related to surface activity and cellular response. Furthermore, key requirements for depositing a coating are listed, and extensively used substrate materials are also described for the reader. Surface preparation is of high importance in order to deposit the coatings successfully, and use of appropriate technique for depositing coatings (especially orthopedic, knee, dental, cardiac, and drug delivery devices) is also provided in the chapter. Various surface characterization techniques are also introduced to facilitate the reader.

Chapter 8 provides the engineering of micro- and nano-fabrication of biomaterials via laser prototyping. Use of laser technology in fabricating neural, ophthalmic and cardiovascular devices is described. Furthermore, making micro-needles via laser technology can be highly useful in providing controlled transdermal delivery of pharmacologic agents and vaccines.

Processing of carbon nanotubes (CNTs)-reinforced hydroxyapatite (HA) via electrophoretic deposition, aerosol deposition, laser processing and plasma spraying is presented in Chapter 9. In order to develop a free-standing HA-CNT composite via sintering, hot pressing and spark plasma sintering are also described. More importantly, the mechanical and tribological characterization (both at macro- and micro-length scale) is elicited. In order to physically perceive the adhesion strength, nano-scratch is used to quantify the adhesion force of bone cells. Furthermore, novel TiO2- and boron-nitride-nanotubes-reinforced HA are also discussed in the chapter.

Chapter 10 deals with the implantable devices (such as bone and dental implants, stents, surgical devices and scaffolds, prosthesis, etc.) that allow the actual usage of bioengineered surfaces in enhancing the quality of life. The role of drug delivery in using the functionalization of specific molecules and using nanoparticles capsules is also presented herewith.

The last section of the book, in Chapter 11, covers the safety, societal and ethical aspects of using nanobiomaterials. Governmental Environment and Health Safety Organization Protocols and related safety hazards are discussed, and an approach toward developing safety protocols for the laboratory environment is listed. Current scenarios in the capability of capturing nanoparticles, and being able to evolve safety measures are presented. In addition, recommendations are provided in order to maintain safety while ethically using biomaterials for enhancing the quality of life.

The construction of these chapters will allow an easy understanding for students, academicians and industrial researchers working in the area of biosurfaces. In particular, this book has been sectioned in following major sections: (i) overview, fundamentals and class of biomaterials, (ii) biosurfaces and their role in initiating first response, (iii) processing and deposition of coatings as biosurfaces, (iv) engineering of biosurfaces (and performance evaluation) for biological applications, and (v) nanosafety and nanoethics.

Hence, this book can: (i) serve as a text book for teaching/academic purposes, (ii) provide research ideas in broader range of topics, while eliciting variety of materials (ceramics, polymers and metals), and biological response (both molecular and cellular), (iii) help adopting commercial technology for processing of biocoatings, (iv) guide in evaluating the performance of coatings, and (v) help implementing safety protocols, and listing ethical aspects of biomaterials.

It is important to mention that this book is an outcome of several years of teaching undergraduate and postgraduate level courses in the area of materials science and engineering, biomaterials processing and characterization, and surface phenomena related to materials. These have laid the foundation...