Drug Release from Novel Rubbery Coatings

Poly(styrene-b-isobutylene-b-styrene) (SIBS) block copolymer, a thermoplastic elastomer, is used in clinical practice as the drug-eluting polymeric coating on the Taxus ® coronary stent. We have been developing new architectures comprising an arborescent arbPIB core synthesized by inimer-type living carbocationic polymerization of isobutylene (IB) by the 4 -( 2 -methoxy-isopropyl)styrene and 4-(1,2-oxirane-isopropyl)styrene inimers in conjunction with TiCl 4 , from which polystyrene is blocked (D_SIBS). These novel self-assembling "double" networks have unique properties. ElectroNanospray ™ , a proprietary technology developed at the University of Minnesota, was used to coat coronary stents with selected D_SIBS polymers loaded with Dexamethasone, a model drug. This paper will demonstrate how drug release profiles can be influenced by both the molecular weight of the DIB midblock and spraying conditions of the polymer-drug mixture.