| The first covalent functionalization of fluorous thin films using the Cu-catalyzed azide-alkyne cycloaddition reaction (CuCAAC, a "click" reaction) is presented. The "clickable" azido or ethynyl fluorous slides were easily prepared by non-covalent immobilization based on strong fluorous interactions between the fluorous-tagged alkynes or azides and the commercial perfluorocarbon-coated glass slides. CuCAAC reaction with the azide- or alkyne-derivatives was readily performed on these "clickable" slides. Using this approach, a variety of biomolecules were attached onto the surfaces under aqueous conditions and in a microarray format.;As compared to the direct fluourous immobilization, an obvious advantage of immobilization of biomolecules via CuAAC reaction is that it can be performed in aqueous buffer solutions to improve solubility and avoid denaturing of the biomolecules. Significantly, we demonstrate that our method may also improve the performance of the functionalized surfaces. Thus, oligo(ethylene) glycol (OEG)-presenting surfaces were prepared by the two immobilization methods, using ethynyl-terminated or fluorous-modified OEG derivatives. XPS and cell adhesion results showed that protein (fibrinogen) adsorbed on the fluorous-OEG modified surfaces. Significantly, the OEG surfaces prepared via CuAAC reaction completely repelled fibrinogen. Furthermore, these surfaces remained effective in preventing adhesion of NIH 3T3 fibroblast cells for up to 8 weeks.;This approach was also applied to present antimicrobial peptides (AMPs) on fluorous-based contact lens. Specifically, LL-25, an AMP with an azido tag, was tethered using the conventional carbodiimide coupling and the CuCAAC reaction. It was observed that although the peptide density for the carbodiimide-immobilized was estimated to be higher as compared to the CuAAC-immobilized, the latter was more effective in preventing bacterial colonization. However, x-ray photoelectron spectroscopy (XPS) revealed gradual desorption of CuAAC-immobilized AMPs, probably due to the insufficient binding strength between the single perfluorocarbon chains with the fluorous surface. To address this issue, a fluoroustagged generation 5 (G5) poly(amido amine) (PAMAM) dendrimer modified with multiple perfluorocarbon chains and terminal alkynes was used to form a stable platform presenting ethynyl groups on the surface. The AMPs immobilized on these platforms via CuAAC reaction prevented the desorption of the AMP on the contact lens while maintaining its vi bactericidal activity against Pseudomonas aeruginosa and non-cytotoxicity on human corneal epithelial cells (HCECs). |
