Degradable, Multifunctional Cardiovascular Implants: Challenges and Hurdles
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Multifunctional Cardiovascular Implants: Challenges and Hurdles Friedrich Jung, Christian Wischke, and Andreas Lendlein
Abstract Polymer-coated and polymer-based cardiovascular implants are essential constituents of modern medicine and will proceed to gain importance with the demographic changes toward a society of increasing age-related morbidity. Based on the experiences with implants such as coronary or peripheral stents, which are presently widely used in clinical medicine, several properties of the next generation of cardiovascular implants have been envisioned that could be fulfilled by multifunctional polymers. The challenge is to combine tailored mechanical properties and rapid endothelialization with controlled drug release in order to modulate environmental cells and tissue. Additionally, degradability and sensitivity to external stimuli are useful in several applications. A critical function in terms of clinical complications is the hemocompatibility. The design of devices with improved hemocompatibility requires advanced in vitro test setups as discussed in depth in this article. Finally, degradable, multifunctional shape-memory polymers are introduced as a promising family of functional polymers that fulfill several requirements of modern implants and are of high relevance for cardiovascular application (e.g., stent technology). Such multifunctional polymers are a technology platform for future cardiovascular implants enabling induced autoregeneration in regenerative therapies.
Introduction The recent demographic development is associated with an increase of atherosclerotic morbidity during the last few decades. Therefore, clinical medicine has to deal increasingly with diseases, leading to a loss of function of important cells, tissue, or organs. In many cases, these diseases cannot be cured using current therapies, and patients have to remain in permanent therapy, causing high costs. Regenerative medicine is a highly interdisciplinary
approach and deals with the restitution, substitution, and regeneration of nonfunctional tissues or organs by biological replacement (e.g., by tissues produced in vitro) or through the stimulation of the body’s own regeneration processes (endogenous regeneration).1–3 An important field in regenerative medicine is the induced autoregeneration of cells or tissues. Here, polymer-based biomaterials are used to selectively enable the
MRS BULLETIN • VOLUME 35 • AUGUST 2010 • www.mrs.org/bulletin
growth of specific cell types, to act as a degradable support and guidance to build up three-dimensional tissue structures,4 or to attract cells and modulate their function by the release of bioactive molecules and by providing a suitable microenvironment.5 An example illustrating the potential of polymeric materials to induce regenerative processes is the full regeneration of a critical defect in a rat stomach using a polymeric implant (AB polymer networks from n-butyl acrylate and poly(ε-caprolactone) dimethacrylate segments).6,7 This development is the result of comprehensive
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