Chemical modifications, implant materials

Chemical etching, porous templates, 171-172 Chemical modifications, implant materials, 147-148... 

Orthopedic and dental implant materials bioceramics, 145-146 chemical modifications, 147-148 comparing mechanical properties of, and bone, 146 conventional, 127 costs, 126-127 current materials, 145-148 fate of implanted device, 140-141 integration into surrounding tissue, 127 integrin expression on osteoblasts, 144 integrins, 143-144 metals, ceramics, and polymers, 145 next generation, 127,148-159... 

Classical polymers have become increasingly used in medicine as components of biomedical devices, but with the development of new techniques for functionaUzalion, more sophisticated polymers have been developed, for instance as constituents of implants and drug delivery. In addition, chemical modification applied to polymers by y-irradiation to create new materials and applications is an effective alternative to reintegrate some polymers whose use has been limited due to problems associated with biocompatibility, toxicity, or bacterial colonization. All monomers and synthetic polymers presented in this chapter and their corresponding abbreviations are given in Table 10.1. 

Surface engineering aims for a defined physical, chemical, or biomolecular modification of material surfaces in order to create biofunctional surfaces that ensure biocompatibility (noninteractive materials) and in many cases additionally bioactivity of the material (interactive biomaterials) for a certain application. The design of appropriate biofunctional surfaces is important for the proper function of biosensors, membranes or implants, for the use as... 

Ion beam-induced chemical modification of polymers, even at low doses, is accompanied by a strong compacting of a polymer host that leads to an increase of the refractive index n [113,114], For instance, in the case of polymethyl methacrylate (PMMA), the relative variation in the refractive index upon ion implantation ranges up to -1-30% [114], which considerably exceeds the changes in the refractive index resulting from ion beam-induced amorphization of a-quartz (A /n = -4%), LaTaOj (An/n = -5%), and other optical materials [114,115]. Moreover, the refractive index of PMMA can be readily controlled because the almost linear An... 

The appearance of this type of bioceramics bom of the need to eliminate the interface movement that takes place with the implantation of bioinert ceramics. Consequently, L. L. Hench proposes in 1967 to the U.S.A. Army Medical Research and Development Command, a research based on the modification of the chemical composition of ceramics and glasses so that they have chemical reactivity with the physiological system and form chemical bond between the adjacent tissue and the surface of implant materials. 

As the basic component of medical textile materials, the structures and properties of the constituent polymers have a significant effect on the biodegradability, biocompatibility, absorbency, antimicrobial property, and other functional performances of the final medical textile products. Functional modifications of polymers have far-reaching effects on the fibers, yams, fabrics, and textile materials that are processed in a series of downstream operations. In order to generate the desired product performance characteristics for their diverse applications such as hygiene, protection, therapeutic, nonimplantable or implantable materials, extracorporeal devices, etc., the chemical and physical structures of the relevant polymers should be engineered to suit their required specifications. 

Although contributions to the above-mentioned international conferences give a fairly complete picture of the state of the art of ion implantation, especially in commercial applications, there are two areas (in addition to that of better understanding of basic physical and chemical effects) on which successful use of ion beam modification of materials depends ... 

Surface modification of a contact lens can be grouped into physical and chemical types of treatment. Physical treatments include plasma treatments with water vapor (siUcone lens) and oxygen (176) and plasma polymerization for which the material surface is exposed to the plasma in the presence of a reactive monomer (177). Surfaces are also altered with exposure to uv radiation (178) or bombardment with oxides of nitrogen (179). Ion implantation (qv) of RGP plastics (180) can greatiy increase the surface hardness and hence the scratch resistance without seriously affecting the transmission of light. 

Substrate Treatment. When the desired image is developed in the resist, the pattern created provides a template for substrate modification. The various chemical and physical modifications currently used can be classified into additive and subtractive treatments. Examples of additive treatments include the insertion of dopants (by either diffusion or ion implantation) to alter the semiconductor characteristics and metal deposition (followed by lift-off or electroplating) to complete a conduction network. In most cases, however, the substrate material is etched by a subtractive process. 

In this chapter we discuss how solid surfaces can be modified. Surface modification is essential for many applications, for example, to reduce friction and wear, to make implants biocompatible, or to coat sensors [405,406], Solid surfaces can be changed by various means such as adsorption, thin film deposition, chemical reactions, or removal of material. Some of these topics have already been discussed, for example in the chapter on adsorption. Therefore, we focus on the remaining methods. Even then we can only give examples because there are so many different techniques reflecting diverse applications in different communities. 

All electrodes react with their environment via the surfaces in ways which will determine their electrochemical performance. Properly selected surface modification can effectively enhance the electrode heterogeneous catalysis property, especially selectivity and activity. The bulk materials can be chosen to provide mechanical, chemical, electrical, and structural integrity. In this part, several surface modification methods will be introduced in terms of metal film deposition, metal ion implantation, electrochemical activation, organic surface coating, nanoparticle deposition, glucose oxidase (GOx) enzyme-modified electrode, and DNA-modified electrode. 

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