Simple degradable cyclodextrin polyester with chelator-based crosslinker for stent-based drug delivery

Cyclodextrins are a class of molecules which inclusion complexes with small hydrophobic drugs, and has historically been used to improve solubility and bioavailability of labile drugs in pharmaceutical applications. More recently, polymerized cyclodextrin has been applied in various applications as implantable drug delivery depots and as medical device coatings (e.g. polymeric hernia meshes) due to their ability to sustain and control drug delivery as well as prevent biofouling. Cyclodextrin polymers as coatings for metal medical devices, like screws or stents, is less explored; due to the high mechanical property mismatch between polymers and metals, a polymer coating is liable to delaminate easily, especially during device deformation. Novel methods for facilitating attachment to metal substrates have been explored, but coating longevity is still an issue, and these methods typically require the use of multiple reagents and complex methods. We report here the development and characterization of a cyclodextrin polymer with a chelator-based crosslinker with respect to appearance, chemistry, drug release profiles, erosion, pH-dependence. We found that increasing the crosslinking ratio (crosslinker:cyclodextrin) slowed down degradation and decreased drug loading as well. Drug release of the anti-restenotic drug sirolimus proceeded for over 4 weeks. The ability of the polymer to stably coat metal stents was verified, and the coating procedure is a simple, single step protocol.