Biocompatibility description

Despite the evidence for the cytotoxicity of CNTs, there are an increasing number of published studies that support the potential development of CNT-based biomaterials for tissue regeneration (e.g., neuronal substrates [143] and orthopedic materials [154—156]), cancer treatment [157], and drug/vaccine delivery systems [158, 159]. Most of these applications will involve the implantation and/or administration of such materials into patients as for any therapeutic or diagnostic agent used, the toxic potential of the CNTs must be evaluated in relation to their potential benefits [160]. For this reason, detailed investigations of the interactions between CNTs/CNT-based implants and various cell types have been carried out [154, 155, 161]. A comprehensive description of such results, however, is beyond the scope of this chapter. Extensive reviews on the biocompatibility of implantable CNT composite materials [21, 143, 162] and of CNT drug-delivery systems [162] are available. 

Fig. 23.5 Aqueous-organic two-liquid-phase system for microbial production of flavour compounds. Here the formation of 2-phenylethanol from L-phenylalanine is exemplarily shown [120]. The organic solvent used for in situ extraction has to be carefully selected on the basis of multiple criteria, such as biocompatibility, non-flammability and legislative regulations. For a more detailed description of flavour production in two-phase systems, see Chap. 24 by Larroche et al.

Water-based barrier dressings are attractive for application to injured tissue because of the biocompatibility between water and tissue. The concept of a water-based dressing initially consisted of latex-type particles of polymer suspended in an aqueous emulsion. The emulsion would be liquid applied to the tissue, water would evaporate and the particles would coalesce to form a continuous film. The rate of evaporation of water is slow compared to solvents as ethanol that was recognized to be a limitation to application time (time to place on the tissue and harden). The following description of miniemulsions (miniEP) involves a batch type... 

While the composition and sequence of the amino acids have been known since 1983 (2,3), methods for increased-scale extraction were not developed until 1985. This scaled production has allowed for the development of single-part adhesive systems (Cell-Tak adhesive) for the immobilization of biologically active moieties to inert substrates. It has also permitted research on two-part adhesive formulations for the bonding of tissues. This paper specifically addresses the biocompatibility issue with descriptions of the immobilization of cells to Cell-Tak protein-coated plasticware, methods for wound closure, and preliminary toxicology data. 

From the description above we can deduce some functions that artificial implants must fulfill if they are to promote nerve regeneration in vivo. A general requirement of biocompatibility, which applies to materials implanted anywhere in the body, demands that the implanted construct must not induce inflammatory reactions or tumor formation and is not rejected or encapsulated by scar tissue. 

An adequate treatment of the subject should involve a discussion of production materials. Thus we have referred to a large variety of materials (i.e., natural and synthetic polymers) for nanofibre fabrication, including the choice and use of them, and a description of how their properties influence processing parameters and properties (biocompatibility, cytotoxicity, etc.) of the product. 

Merritt, K. (1986) Chapter 6. Immunological testing of biomaterials. Techniques of Biocompatibility Testing, D.F. Williams (ed.), Vol. II, CRC Press, Boca Raton Description of possible test methods. 

The preceding description of the factors which together determine the biocompatibility of an implant shows the diversity of the processes. Until now it has not been possible to completely understand these processes or to comprehend them quantitatively. This understanding is, however, a precondition for the development of biocompatible materials and the prevention of unwanted reactions. 

The description of contact guidance (i.e., the cell reaction with the topographical features in its local environment) in mammalian cells dates back to 1964 [26]. Since then, thanks to the development of various techniques for the topographical patterning of biocompatible materials, an increasing number of cell types have been shown to modulate their behavior when contacting flat or topographically-patterned surfaces [27]. 

Decisions will be needed to resolve conflicting information sources and arrive at a concise description of the medical factors, user needs, and purpose(s) to be addressed by the medical device. Following these decisions, it is necessary to define, from a black box perspective, the requirements of the medical device in measurable engineering terms. The actual requirements in the DIR will fall into two broad categories the standards that the product shall meet such as sterility, biocompatibility, International electrical standards and American National Standards Institute (ANSI), etc., and those specific to the medical device (i.e., functional, performance, and interface requirements). 

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