Synthesis and properties of arborescent polyisobutylene derivatives and a paclitaxel conjugate: Towards stent coatings with prolonged drug release

• Arborescent polyisobutylene was functionalized to afford different derivatives.
• Acid-functionalized polyisobutylene was conjugated to the drug paclitaxel.
• Covalent conjugation slowed drug release, prolonging the lifetime of the coating.
• Polar groups or paclitaxel affected mechanical and rheological properties.
• Arborescent polyisobutylene–paclitaxel conjugates are potential stent coatings.

Polyisobutylene (PIB) and its copolymers are used in a wide range of commercial products owing to their high chemical stability, impermeability, elasticity, and biocompatibility. The development of arborescent PIB (arb-PIB) opens many new possibilities for tuning PIB’s properties and for introducing new functionalities. In this work, arb-PIB with short isoprene-rich terminal sequences (arb-PIB-co-IP) was functionalized to provide arborescent epoxide, allylic alcohol, and carboxylic acid derivatives of PIB. The carboxylic acid derivative was used to conjugate the antiproliferative agent paclitaxel (PTX) for investigation as a potential vascular stent coating. The thermal, tensile, and rheological properties of all of the functionalized arb-PIB materials were studied and compared to their linear analogues in order to gain insight into the effects of polymer architecture on these properties as well as to determine their suitability as potential medical device coatings. A coating using the PTX conjugate was found to release PTX much more slowly than control formulations with physically encapsulated drug, yet was still able to prevent cell adhesion and proliferation on their surfaces.

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