In vivo and in vitro characterization of poly(styrene‐b‐isobutylene‐b‐styrene) copolymer stent coatings for biostability, vascular compatibility and mechanical integrity

Abstract

The TAXUS Express 2 Paclitaxel Eluting Coronary Stent System employs a coating consisting of the thermoplastic elastomer, poly(styrene-b-isobutylene-b-styrene; SIBS), selected for its drug-eluting characteristics, vascular compatibility, mechanical properties, and biostability. This study was conducted to evaluate the impact of different SIBS (17-51 mole % styrene) compositions on mechanical properties, chemical stability, and vascular compatibility. Mechanical property (stress-strain measurements) and stability studies were conducted on polymer films with five different styrene contents (17, 24, 32, 39, and 51 mole %). The ultimate tensile strength did not change significantly with composition, but the elongation at break decreased with increased styrene content. A pulsatile fatigue test further confirmed the mechanical stability of SIBS up to 39 mole % styrene. The vascular compatibility of five different SIBS compositions was assessed using SIBS-only coated stents, in the coronary and carotid arteries in a porcine model study. The stability of the vessel wall, rate/degree of endothelialization, inflammation, and thrombus at timepoints from 30 to 180 days were evaluated. The results confirm vascular compatibility over the range of 17-51 mole % styrene.

Synthesis of Poly(methyl methacrylate)-poly(poly(ethylene glycol) methacrylate)-polyisobutylene ABCBA Pentablock Copolymers by Combining Quasiliving Carbocationic and Atom Transfer Radical Polymerizations and Characterization Thereof

“…properties, it is of special importance that both polymers possess non-immunogeneity and bioand blood compatibility (6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17). For all these reasons, it is expected that the integration of these two types of polymer segments into one macromolecule may lead to a variety of new application possibilities.…”

Encapsulation of paclitaxel in ultra-fine nanoparticles of acrylic/styrene terpolymer for controlled release

“…The similarities of hydrophobic characteristics between PTX and monomers of styrene and methyl methacrylate supports facile encapsulation of PTX and provides efficient drug loading in the poly(MMA-ST-AA) nanospheres. Previous studies separately demonstrated that PTX is compatible either with co-polymers consisting of MMA or ST [8,[26][27][28].…”

The effect of water absorption on the viscoelastic properties of poly(styrene-block-isobutylene-block-styrene) for use in biomedical applications

“…Styrene blocks give the material a glassy region providing its mechanical rigidity, while the isobutylene blocks provide enhanced chain mobility. Compositions with higher content of styrene have behavior closer to that of a toughened plastic, while the higher isobutylene compositions behave as an elastomeric plastic [1,2,[4][5][6].…”

“…Poly(Styrene-block-Isobutylene-block-Styrene) (SIBS) copolymer is a thermoplastic elastomer that has been proposed to be used in biomedical applications because it is extremely biocompatible and has a very low foreign body reaction [1][2][3]. Mechanical properties of SIBS are similar to polyurethanes and silicone rubbers, which make it ideal for use in stents, drug carriers, MIDI-tubes, heart valves, etc.…”

“…Biocompatibility is not affected by changing the block composition of SIBS [1], which allows tailoring of the mechanical properties according to the specific needs of different implants. Also, it has been shown that the hemocompatiblity can be further improved by modifying SIBS with phospholipids, resulting in a reduction of platelet adhesion by a factor of 10 but simultaneously reducing tensile strength by 30% [7].…”