Molecular design and patterning of biosurfaces on poly(tetrafluoroethylene) (PTFE)

Nattharika Aumsuwan

Abstract

This dissertation describes the design, synthesis, and development of biocompatible poly(tetrafluoroethylene) (PTFE) surfaces that exhibit anti-microbial, anticoagulant, and dual functional surface properties. It consists of two parts: (1) design, synthesis, and analysis of antimicrobial and anti-coagulant PTFE surfaces, and (2) controllable micropatterning of anti-microbial and anti-coagulant species on the surface. PTFE was modified by Ar microwave plasma reactions in the presence of maleic anhydride, which upon hydrolysis creating COOH groups. These COOH primers were utilized as a platform for further surface reactions to attach polyethylene glycol (PEG) spacers, and penicillin (PEN) or ampicillin (AM) onto the PTFE surfaces. The use of a PEG spacer facilitates enhanced antimicrobial effectiveness of the antibiotics by increasing their mobility, allowing easier contact with the bacteria. Utilizing spectroscopic analysis combined with scanning electron microscopy these studies showed for the first time covalent attachment of PEN or AM leading to antimicrobial activities against Gram (+) and/or Gram (-) bacteria. Such chemically and morphologically modified PTFE surfaces showed effectiveness against Gram (+) Staphylococcus aureus and AM-modified PTFE surface are effective against Gram (+), Staphylococcus aureus, Bacillus thuringiensis, and Enterococcus faecalis, and Gram (-), Escherichia coli, Pseudomonas putida, and Salmonella enterica bacteria. Anti-coagulant PTFE properties were achieved by covalent attachment of alternating multilayers (CAM) of heparin (HP) and PEG, with homogenous coverage and enhanced hemocompatibility, as manifested by a 75¡√ì1% decrease of the platelet adhesion and a 60¡√ì5% decrease of platelet activation. Finally, dual functional PTFE surfaces were generated by the simultaneous inkjet printing of biotinylated ampicillin (B-AM) and biotinylated heparin (B-HP) on streptavidin (STR) functionalized surfaces. Using this bioconjugation approach dots with a spatial resolution of 20 μm were printed side-by-side and in an alternating stripe pattern. The micropatterned surface showed antimicrobial activity against S. aureus bacteria.