Cardiovascular implants biocompatibility

Low flow in vivo venous modds have been suggested for hematocompatibiUty evaluation. However, these systems are not appropriately and adequatdy justified for use in assessing the long-term biocompatibility required for cardiac and cardiovascular implants. 

Hydrogels of CNCs have many desirable properties, including low cost, nontoxicity, hydrophilicity, biocompatibility, and biodegradability, all of which contribute to their potential applications in bioengineering and biomedicine. For example, CNC dispersed in a solution of cellulose, sodium hydroxide, and urea formed a gel that steadily released bovine semm albumin into a simulated body fluid [161]. Nanocomposites of CNC and poly(vinyl alcohol), a hydrophilic biocompatible polymer, exhibited a broad range of mechanical properties that could be tuned to mimic those of cardiovascular tissues and, therefore, have potential applications as cardiovascular implants [162]. 

Cardiovascular tissue engineering aims to create functional tissue scaffolds that can re-establish the structure and function of injured sites of the cardiovascular system. A considerable amount of cardiovascular therapeutics, particularly for major and serious disorders, involves the use of devices. Some of these may be implanted by surgery, whereas others are inserted via minimally invasive procedures involving catheterization. Although different synthetic materials have been used for the development of cardiovascular devices, PUs have several advantages over the others. Besides their biocompatibility and their mechanical flexibility [100-103], PUs have very high flexural endurance compared to most elastomers, making them prime candidates for cardiovascular implants. 

A potential application of BOSS nanocomposites is the coating of implants. Farti-cularly cardiovascular implants got a great deal of interest [102]. The use of the inorganic structures in biocompatible nanocomposites resulted in improved hemocompatibility, antithrombogenicity, calcification resistance, reduced inflammatory response, as well as the already known enhanced mechanical and stuface properties. For example, FOSS/poly(carbonate-urea)urethane nanocomposites were prepared to coat NiTi stent alloys, which enhanced surface resistance and improve biocompatibility [103]. 

The conclusion drawn from the above-discussed features of native endothelium is that—where feasible—construction of host endothelium on the surface of synthetic implants—i.e. engineered endothelialization—may present a promising pathway for fundamentally resolving the biocompatibility and bio-functionality of artificial cardiovascular transplantation. This proposed biocompatibility is, however, not simply thromboresistance (or blood compatibility) plus blood-cell compatibility, but a real bioactive, self-renewable and specifically functional alliance of tissues and synthetics. 

This chapter addresses the application of polymeric biomaterials in the context of implantable devices intended for long-term functionality and permanent existence in the recipients. Basic concepts of biocompatibility as well as mechanical and structural compatibility are discussed to provide appropriate background for the understanding of polymer usage in cardiovascular, orthopedic, ophthalmologic, and dental prostheses. Furthermore, emerging classes... 

State of the art testing at the time, but we wanted more long term in vivo data for cardiovascular. In vitro and ex vivo testing demonstrated that the materials were biocompatible and stable in the intended environment (as it was understood at the time) [6]. Just to be sure, however, we implanted the materials in the subcutis of rabbits for 2 years, conducting extensive characterization tests as a function of time. No untoward biocompatibility or biostability issues were revealed. Device tests were conducted in canines for 12 weeks, which had been shown to be sufficient time to characterize acute and chronic performance. Human clinical evaluations over 1-2 years (depending on the models) demonstrated that the devices had superior performance compared to their predecessors [7, 8]. Four polyurethane-insulated lead models were market released in the United States in April 1980 with FDA approval. 

Diagnostic and therapeutical treatments implicate the contact between tissue, blood and the implanted material. In the cardiovascular field, a variety of biomaterial is implanted in heart and vessels, such as catheters, stents, heart valves and sondes for pacemakers and defibrillators. Using polymers for new technologies has been a revolutionary advance in the therapy of cardiovascular disease [47]. Nevertheless, there is increasing evidence that the polymer coating could be responsible for adverse effects (e.g. in-stent-restenosis, stent thrombosis, chronicle foreign body reactions). Therefore, a feasible biocompatible material should provide a complete re-endothelialisation of the surface, less thrombogenicity as well as anti-inflammatory properties in order to improve clinical outcomes. 

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