Novel Polyisobutylene-Based Materials and Surfaces; Enzyme-Catalyzed Functionalization and ?Modular? Surface Construction

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TECHNICAL SUMMARY:This award, co-funded by the Division of Materials Research and the Office of International Science and Engineering, aims at the synthesis and characterization of novel self-assembling nanostructured thermoplastic elastomeric (TPE) biomaterials based on polyisobutylene (PIB). Specifically, efforts to synthesize new "Entropy-driven" TPEs (ENTPE) will continue. Under the current NSF support it was discovered that the dendritic (arborescent or tree-like) arbPIB midblock of ENTPEs facilitates phase separation and TPE behavior even with very short plastic and elastomeric end blocks. These novel ENTPE materials were further reinforced with nano-size fillers (carbon and silica) to yield strong rubbery nanocomposites (ENTPEC), and their biocompatibility was demonstrated in vitro and in vivo in rabbits. Based on this discovery, new ENTPEs will be synthesized with short end blocks, capable of hydrogen bonding (e.g., polypeptides). Compounding these materials with nanofillers will yield new ENTPEC nanocomposites. In order to control surface chemistry and patterning for improved tissue integration, a new "modular" approach using ElectroNanoSprayingTM is proposed, which allows the construction of gradient surfaces with various chemistries and topologies. Spraying ENTPE onto the surface of ENTPEC will yield well-controlled nanopatterns of the same chemistry. Surface chemistry will be controlled by spraying low molecular weight (MW) functionalized PIBs (PIB-F) where F is a biologically active compound (nucleic acid base, peptide, protein, etc.) onto the surface of ENTPECs. The PIB-Fs will be precision synthesized from PIB-OH made by living carbocationic polymerization and functionalized using a novel enzyme-catalyzed transesterification process that yields complete conversion under mild conditions this also emerged from the current grant. The "modular" approach will give unprecedented control over surface chemistry and surface patterning independently, and will contribute to new fundamental understanding of the effects of surface properties on the biocompatibility of polymeric materials. NON-TECHNICAL SUMMARY:This project is aimed at the synthesis and characterization of novel biomaterials based on polyisobutylene (PIB). These materials are soft and transparent like silicone rubber, but self-assemble into a network without any chemical treatment which is necessary to make silicone rubber. In 2004, one PIB-based material was FDA-approved as the coating on drug-eluting coronary stents. More than a million of those stents have been implanted into patients, saving lives. The proposed new materials will have improved combination of properties. In addition, a new approach to surface modification to improve biocompatibility will be tested in this project. For this goal new polymers will be synthesized via "green polymer chemistry" using enzymes as catalysts, and sprayed to the surface of the novel biomaterials. This new "modular" approach will give independent control over surface chemistry and patterning, providing unprecedented insight into the effect of these properties on biocompatibility. The new materials may replace silicone rubber in certain applications (for example, as the shell of breast implants where impermeability is required). This project is interdisciplinary, building on collaborators (Nanocopoeia Inc. Minnesota, BioMedical Research Associates Akron, the University of Washington, Pomeranian Medical Academy of Poland, University of Bordeaux, France). It is complementary to a recently approved grant by German Research Foundation (DFG) as well as the grant approved by the Polish Ministry of Science and Education, to test various properties of the new biomaterials. The grant will support 1 partial female Post-doctoral fellow (Nanocopoeia's NSF grant will complement this to full time), four Ph. D. students (3 Americans - two of them females, one Hispanic), future REU (Research Experience for Undergraduates) students, an RET (Research Experience for Teachers), and high school students. It will also support international student exchanges and project meetings directly, and international students indirectly. The project will expose students to a great variety of scientific disciplines (polymer chemistry, organic chemistry, material science, biochemistry, surface science, polymer engineering, biomedical engineering, proteomics etc.). They will also have a chance to carry out part of their research in Germany, Poland and Ireland. Exposure to different cultures, organizations and work ethics will prepare the students to work better in the global economy, making them more attractive to potential employers. We will also embark on a new program connecting science and art, in collaboration with the Myers School of Art at the University of Akron to broaden the horizon for students of both disciplines.