Abstract

Biomaterials are defined as nonviable materials and devices intended to interact with biological systems.[1] Since these interactions occur through their surfaces and since surface properties affect cellular response and proliferation,[2] it is vitally important to control the surface properties of biomaterials. Chemical vapor deposition (CVD) polymerization is a surface modification technique that allows for fabrication of thin films on substrates.

Reactive coatings obtained via CVD polymerization of [2.2]paracyclophanes have recently shown precise control over surface chemistries, independently from the bulk material.[3] Substituted [2.2]paracyclophanes serve as precursors for producing functional polymer films, so-called “reactive coatings”. These coatings carry anchor groups (e.g. ATRP initiator, alkynes, aldehyde) for further chemical surface modification, especially surface initiated controlled polymerizations techniques.

As synthetic zwitterionic polymer coatings are able to sustain long-term human embryonic stem cell growth,[4] the development of controllable and well-defined zwitterionic polymer coatings is of major interest. Our project aims to expand surface modification via CVD-polymerization for the production of functional coatings suitable for cell culture applications.

In particular, efforts have been focused on the following: 1) The synthesis and CVD-polymerization of substituted [2.2]paracyclophanes bearing suitable functional groups for surface-initiated controlled radical polymerization (ATRP, RAFT). 2) The synthesis of new, potentially bioactive methacryl-based zwitterionic monomers. 3) The application of these zwitterionic monomers in surface-initiated controlled radical polymerization (ATRP, RAFT) using vapor-based initiator coatings. 4) Evaluation of these zwitterionic polymer coatings as potential cell culture substrates. Here we describe new synthetic routes used to generate a library of novel zwitterionic monomers.

Additionally, [2.2]paracyclophanes with functional groups suitable for initiating ATRP or RAFT polymerizations were successfully synthesized and then polymerized onto different substrates (e.g. Au, Si) as a base coating. Subsequently, the coatings with an ATRP initiator group were exploited in the controlled grafting-from polymerization of this library of newly synthesized zwitterionic monomers.

In contrast, the surfaces used to initiate RAFT polymerization required an alkyne CVD coating in combination with subsequent binding of clickable RAFT agents. Going forward, these novel biomaterials may show promise as cell culture substrates.

[1] D. F. Williams, Definitions in Biomaterials. Progress in Biomedical Engineering 4, Elsevier Amsterdam, 1987.

[2] D. Falconnet, G. Csucs, H. M. Grandin, M. Textor, Biomaterials. 2006, 27, 3044.

[3] H.-Y. Chen, M. Hirtz, X. Deng, T. Laue, H. Fuchs, J. Lahann, J. Am. Chem. Soc. 2010, 132, 18023.

[4] L. G. Villa-Diaz, H. Nandivada, J. Ding, N. C. Nogueira-de-Souza, P. H. Krebsbach, K. S. O´Shea, J. Lahann, G. D. Smith, Nat. Biotechnol. 2010, 28, 581.