Polyurethane devices for drug delivery in cardiovascular applications

5 Polyurethane devices for drug delivery in cardiovascular applications 

Due to the high versatility of their chemical structure (which allows the modulation of their physicochemical properties and degradation kinetics by simply varying the building blocks), biodegradable and biostable PURs have been proposed for drug delivery devices (Sartori et al., 2014 Chemg et al., 2013). 

In the case of biostable PURs, that is, materials that remain stable under physiological conditions, drug delivery is mainly controlled by drug diffusion from the material structure. In contrast, for biodegradable PURs the release rate of pharmacologically active molecules is mostly governed by the degradation rate of the polymer, which in turn depends on several different parameters (Storey and Hickey, 1994). 

Several authors have studied the dependence of the degradation rate on the composition and molecular weight of the macrodiol, the crystallinity of the polymer, and the presence of enzymatically cleavable sequences. 

It has been shown that PURs with hydrophilic soft segments are more susceptible to hydrolytic degradation due to facilitated water uptake. Moreover, more crystalline polymers and polymers prepared with higher molecular weight biostable macrodiols have lower degradation rates (Chemg et al., 2013). 

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