Biomaterial biocompatibility

Keywords carbon nanotubes, biomaterials, biocompatibility, toxicity, nanomaterials... 

Biological environment must not impair the functioning of the biomaterial Biocompatibility... 

In the scientific literature, we often describe the evaluation of biomaterials biocompat-ibUity by tests that should be predictive of the clinical outcome. Such tests make sense from a regulatory standpoint whereby biocompatibility is assessed by a series of tests to determine the potential toxicity resulting from the contact of the components of medical devices or combination products with the body. 

The use of collagen as biomaterial, biocompatible and bioresorbable for the connective tissues prosthesis in which collagen is the basic protein is very well known. 

Similarly, after a longer time of incubation, no significant changes in the cell proliferation rate was detected, as can be seen in the data for 72 h (Figure 13). In fact, this was expected due to the biocompatible nature of xylan. As a natural polyssacharide, this type of biomaterial is considered to be highly stable, non-toxic and hydrophilic (Liu et al., 2008). Accordingly, the alkaline extraction of xylan from corn has proved to be a safe approach for obtaining the polymer with no relevant toxicity (Unpublished data). 

Tessier, P. Y., Pichon, L., VUlechaise, P, Linez, P., Angleraud, B., MubumbUa, N., Fouquet, V, Straboni, A., Milhet, X., and Hildebrand, H. F., Carbon Nitride Thin Films as Protective Coatings for Biomaterials Synthesis, Mechanical and Biocompatibility Characterizations, Diamond Relat. Mater, Vol. 12,2003,pp. 1066-1069. 

El Fray, M., Prowans, P., Puskas, J.E., and Altstadt, V. Biocompatibility and fatigue properties of polystyrene-polyisobutylene-polystyrene, an emerging thermoplastic elastomeric biomaterial. Biomacromolecules, 7, 844-850, 2006. 

Sundback CA, Shyu JY, Wang YD, Faquin WC, Danger RS, Vacanti JP, and Hadlock TA. Biocompatibility analysis of poly(glycerol sebacate) as a nerve guide material. Biomaterials, 2005, 26, 5454-5464. 

Our interest in the synthesis of poly (amino acids) with modified backbones is based on the hypothesis that the replacement of conventional peptide bonds by nonamide linkages within the poIy(amino acid) backbone can significantly alter the physical, chemical, and biological properties of the resulting polymer. Preliminary results (see below) point to the possibility that the backbone modification of poly(amino acids) circumvents many of the limitations of conventional poly(amino acids) as biomaterials. It seems that backbone-modified poly (amino acids) tend to retain the nontoxicity and good biocompatibility often associated with conventional poly (amino acids)... 

Although the initially reported tissue compatibility tests for subcutaneous implants of poly(BPA-iminocarbonate) were encouraging (41,42), it is doubtful whether this polymer will pass more stringent biocompatibility tests. In correspondence with the properties of most synthetic phenols, BPA is a known irritant and most recent results indicate that BPA is cytotoxic toward chick embryo fibroblasts in vitro (43). Thus, initial results indicate that poly(BPA-iminocarbonate) is a polymer with highly promising material properties, whose ultimate applicability as a biomaterial is questionable due to the possible toxicity of its monomeric building blocks. 

Yang CY, Song BB, Ao Y et al (2009) Biocompatibility of amphiphilic diblock copolypeptide hydrogels in the central nervous system. Biomaterials 30 2881-2898... 

In an attempt to identify more biocompatible diphenols for the design of degradable biomaterials, we studied derivatives of tyrosine dipeptide as potential monomers. After protection of the amino terminus and the carboxylic acid terminus, the reactivity of tyrosine dipeptide (Figure 1) could be expected to be similar to the reactivity of industrial diphenols. Thus, derivatives of tyrosine dipeptide could be suitable replacements for BPA in the synthesis of a variety of new polymers that had heretofore not been accessible as biomaterials due to the lack of diphenolic monomers with good biocompatibility. 

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. 

Successful applications of materials in medicine have been experienced in the area of joint replacements, particularly artificial hips. As a joint replacement, an artificial hip must provide structural support as well as smooth functioning. Furthermore, the biomaterial used for such an orthopedic application must be inert, have long-term mechanical and biostability, exhibit biocompatibility with nearby tissue, and have comparable mechanical strength to the attached bone to minimize stress. Modem artificial hips are complex devices to ensure these features. 

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