Page 20 - Magnesium-based supports for stem cell therapy of vascular disease - Mónica Echeverry Rendón

CHAPTER 2
The multidisciplinary nature of stent development and clinical applications urged us to bridge clinical science, bio- logical concepts, chemistry, engineering and materials sciences in the prospect of current and future treatment of vascular disease Fig.1.
Fig.1 Novel concepts and technology are emerging in order to find new alternatives for patient that need reliable and fast solutions for a plethora of diseases. Implantable medical devices have frequently used to repair or replace damaged tissues and organs. In this case the interaction of biomaterials with the implant tissue microenvironment will induce specific biological responses. Bioactive interfaces can lead the regeneration or functional recovery of damaged tissue in terms of time, quality and cost. The multidisciplinary understanding of the problem is crucial in the different stages of the process.
2. Biomaterials for stent manufacture
Metals are ubiquitously used to manufacture vascular stents, due to their favorable mechanical properties (e.g. toughness and resilience) and near absent chemical reactivity in the extreme corrosive biological environment. Yet, recurrence of restenosis is a problem, while thrombosis risk is increased too, in particular for degradable BMS [19]. Thus, the use of current conventional BMS, can be considered as a transitory solution because it can lead to future problems once insertion in the lumen of the vessel is completed [24]. This challenge has been recently addressed by introducing the slow-release of surface-loaded drugs on stents [21,22]. This approach improves the biological response of stents, however this solution is at best transient because the drug release is temporary. In addition, there is an increased risk for thrombus formation compared to traditional bare metal stents [21,23,24]. As a consequence of this problem, new designs and formulations of stents have been examined with the purpose to generate a biode- gradable material that can heal and repair the tissue and subsequently resorbs without inducing an adverse foreign body response (FBR) [10,15,25–28]. Thus, the device needs to be a temporal vascular scaffold which allows radial support while simultaneously avoiding vessel recoil. Previous studies have identified magnesium as a potentially suitable material for use in cardiovascular applications due to its biological and structural properties, however mag- nesium in its pure state is limited by its highly reactive chemical condition. Obviously, adjusting the chemical nature prevents adverse tissue responses and will be discussed below. Important design issues for optimum performance
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