Implantable medical devices biological structures

This example of vascular grafts devices points out the evolution of fibrous implantable medical devices and highlights the great potential offered by each scale level of fibrous structures for biocompatibility improvements. Fibers as well as whole fibrous stmctures should be considered as implantable devices that have inherent abilities to interact with the biological environment at each of the three predetermined scale levels. Study of characteristics and specificities of fibers, fibrous siuface, and fibrous volume should then provide a more forward-looking approach in the textile substitute s area for design and achievement of smart medical implantable textile devices. 

All these features, related to fibrous cohesive structures, are determinant in the whole textile strucmre final behavior. To gauge the impact of fibrous cohesiveness on implantable medical devices, each specific characteristic of interlaced fiber strucmres has to be correlated with the biological responses to which it relates. 

Depending on the nature of used material in fibrous implantable medical device design, degradation products take different forms. As previously described, polymer degradation usually results in monomer solubilization. Degradation of metallic material occurs by metal ions released at exposed weak surfaces of the material. Moreover, degradation of material in the biological environment may happen at the structural level and be associated with debris and particle release. 

Before implantation several in vitro tests were performed. For evaluation of a possible toxic reaction, we investigated the material and the whole devices in vitro with cell culture methods. Direct contact and extraction tests with a mouse fibroblasts cell line (L 929) and a neuroblastoma cell line (neuro-2-a) were performed according to the international standard ISO 10993 ( Biological Evaluation of Medical Devices ). The materials and devices showed no toxicity, i.e. no significant differences in membrane integrity of the cell membranes, mitochondrial activity and DNA synthesis rate. The neuro-2-a cell line is so sensitive that even small changes in process technology are detectable. The flexible polyimide structures proved to be non toxic. 

Chapter 5 by Ishihara and Fukazawa focuses on polymers obtained from 2-methacryloylo>yethyl phosphorylcholine (MPC) monomer. Indeed, the molecular design of MPC polymers with significant functions for biomedical and medical applications is summarized in detail. It is especially shown that some MPC polymers can provide artificial cell membrane-like structures at the surface as excellent interfaces between artificial systems and biological systems. In the clinical medicine field, MPC polymers have been used for surface modification of medical devices, including long-term implantable artificial organs to improve biocompatibilily. Thus some MPC polymers have been provided commercially for these applications. 

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