title: Synthesis, characterization, properties, and drug release of poly(alkyl methacrylate-b-isobutylene-b-alkyl methacrylate).
abstract: Polyisobutylene (PIB)-based block copolymers have attracted significant interest as biomaterials. Poly(styrene-b-isobutylene-b-styrene) (SIBS) has been shown to be vascularly compatible and, when loaded with paclitaxel (PTx) and coated on a coronary stent, has the ability to deliver the drug directly to arterial walls. Modulation of drug release from this polymer has been achieved by varying the drug/polymer ratio, by blending SIBS with other polymers, and by derivatizing the styrene end blocks to vary the hydrophilicity of the copolymer. In this paper, results are reported on the synthesis, physical properties, and drug elution profile of PIB-based block copolymers containing methacrylate end blocks. The preparation of PIB-poly(alkyl methacrylate) block copolymers has been accomplished by a new synthetic methodology using living cationic and anionic polymerization techniques. 1,1-Diphenylethylene end-functionalized PIB was prepared from the reaction of living PIB and 1,4-bis(1-phenylethenyl)benzene, followed by the methylation of the resulting diphenyl carbenium ion with dimethylzinc (Zn(CH(3))(2)). PIB-DPE was quantitatively metalated with n-butyllithium in tetrahydrofuran, and the resulting macroinitiator could initiate the polymerization of methacrylate monomers, yielding block copolymers with high blocking efficiency. Poly(methyl methacrylate-b-isobutylene-b-methyl methacrylate) (PMMA-b-PIB-b-PMMA) and poly(hydroxyethyl methacrylate-b-isobutylene-b-hydroxyethyl methacrylate) (PHEMA-b-PIB-b-PHEMA) triblock copolymers were synthesized and used as drug delivery matrixes for coatings on coronary stents. The PMMA-b-PIB-b-PMMA/PTx system displayed zero-order drug release, while stents coated with PHEMA-b-PIB-b-PHEMA/PTx formulations exhibited a significant initial burst release of PTx. Physical characterization using atomic force microscopy and differential scanning calorimetry of the formulated PMMA-b-PIB-b-PMMA coating matrix indicated the partial miscibility of PTx with the PMMA microphase of the matrix.
authors.affiliation: Department of Chemistry, University of Massachusetts Lowell, One University Avenue, Lowell, Massachusetts 01854, USA.
authors.forename: Jae Cheol
authors.initials: JC
authors.lastname: Cho
authors.forename: Guanglou
authors.initials: G
authors.lastname: Cheng
authors.forename: Dingsong
authors.initials: D
authors.lastname: Feng
authors.forename: Rudolf
authors.initials: R
authors.lastname: Faust
authors.forename: Robert
authors.initials: R
authors.lastname: Richard
authors.forename: Marlene
authors.initials: M
authors.lastname: Schwarz
authors.forename: Ken
authors.initials: K
authors.lastname: Chan
authors.forename: Mark
authors.initials: M
authors.lastname: Boden
mesh_terms: D002152:Calorimetry, Differential Scanning; D004337:Drug Carriers; D009682:Magnetic Resonance Spectroscopy; D018625:Microscopy, Atomic Force; D008855:Microscopy, Electron, Scanning; D011090:Polyenes / Q000138:chemical synthesis* / Q000737:chemistry; D011108:Polymers / Q000138:chemical synthesis* / Q000737:chemistry; D013056:Spectrophotometry, Ultraviolet; D015607:Stents
chemical_list: D004337:Drug Carriers; D011090:Polyenes; D011108:Polymers; C008967:polyisobutylene