Structures of Biomaterials

The blood-materials interactions section contains a review article dealing with surface characterization. Consideration of the surface structure of biomaterials is critical to every study in this volume. This section contains 16 chapters dealing with the choice of in vivo and in vitro methods of biomaterials evaluation, biomaterials selection and modification, and cellular interactions with candidate surfaces. Individual papers dealing with the use of dogs, baboons, and goats for in vivo blood-materials evaluation can be found together with in vitro methods. There are also several contributions on polyurethanes, which are prime candidates for use in blood contacting devices. 

The structure of biomaterials deforms when dried. This is due to the surface tension of water during drying. In order to avoid this phenomenon, evaporation can be done at a critical point where there is no surface tension observed. Unfortunately, it is not practical because the critical point of water is 374°C at 22.06 MPa. In contrast, the critical point of carbon dioxide is 31.4°C at 7.375 MPa. 

Bio-inspired chemistry is not, however, confined to attempts to mimic the exquisite hybrid structures of biomaterials. The advent of... 

Understanding the relationship between molecular structure and materials piroperties or biological activity is one of the most important facets of biomaterials synthesis and new-drug design. This is especially true for polyphosphazenes, where the molecular structure and properties can be varied so widely by small modifications to the substitutive method of synthesis. 

Skinner, J. C., Prosser, H. J., Scott, R. P. Wilson, A. D. (1986). Adhesion of carboxylate cements to hydroxyapatite. I. The effect of the structure of aliphatic carboxylates on their uptake by hydroxyapatite. Biomaterials, 7, 438-40. 

Fig. 2.3 Concept of hybridization of inorganic structures with biomaterials to provide bio-silica hybrids.

In this volume, we have collected a series of important critical articles on the present and future of biomaterials science as viewed by some of the leading chemical engineers of the field. It was not our intention to cover all aspects of biomaterials science but rather to unify certain synthetic, structural, and biological topics, and to point out the significant contributions of chemical engineers to the field. It is not a coincidence that this book is part of the well-known series of Advances in Chemical Engineering. 

II. Structure of Three-dimensional Polymeric Networks as Biomaterials... 

In this second volume, following volume no. 107, we have collected review articles by leading authorities in the field of biomaterials who address the structure, properties and medical uses of a number of new polymers. All reviews have a strong emphasis on the polymer aspects of the biomedical development and offer ample evidence of how the structure can influence the medical behavior of these systems. 

Knowledge of the surface structure of CaHAP panicles is fundamentally needed not only in medical and dental sciences but also in application of synthetic CaHAP particles to bioceramics and adsorbents for biomaterials, because the affinity of CaHAP surface to biomaterials is an important factor in all the cases. The surface structure of CaHAP was investigated by various means including infrared (IR) (38,39), NMR (40). TPD (41), and XPS (42). Among these methods, IR spectroscopy is most appropriate for the surface characterization of CaHAP particles. 

Figure 5.125 Structure of collagen fibers based on collagen molecule, microfibrils and fibrillar aggregation. Reprinted, by permission, from I. V. Yannas, in Biomaterials Science, B. D. Ratner, A. S. Hoffman, F. J. Schoen, and J. E. Lemons, eds., p. 86. Copyright 1996 by Academic Press.

The increasing demand for synthetic biomaterials, especially polymers, is mainly due to their availability in a wide variety of chemical compositions and physical properties, their ease of fabrication into complex shapes and structures, and their easily tailored surface chemistries. Although the physical and mechanical performance of most synthetic biomaterials can meet or even exceed that of natural tissue (see Table 5.15), they are often rejected by a number of adverse effects, including the promotion of thrombosis, inflammation, and infection. As described in Section 5.5, biocompatibility is believed to be strongly influenced, if not dictated, by a layer of host proteins and cells spontaneously adsorbed to the surfaces upon their implantation. Thus, surface properties of biomaterials, such as chemistry, wettability, domain structure, and morphology, play an important role in the success of their applications. 

One strategy is to fabricate a template structure using polymeric material (thus, using the same chemistry as described in Sects. 5.2 and 5.3) and back-fill or coat this structure with inorganic materials. For example, surface modification, followed by electroless deposition of Ag [217-219] or Cu [220], or by chemical reduction of Au solutions by surface functionalities [220], has been used to obtain metallized structures, while infiltration of polymeric photonic bandgap-type structures with Ti(0 Pr)4 solution, followed by hydrolysis and calcination, has been used to obtain highly refractive inverted Xi02 structures [221]. Au has also been deposited onto multiphoton-patterned matrices of biomaterials [194]. 

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