| Abstract
| - The temperature-responsive behavior of poly(N-isopropyl acrylamide) (pNIPAM) directly affects theattachment and detachment of cells cultured on these surfaces. At culture temperatures, cells behavesimilarly to those on tissue culture polystyrene (TCPS), while at room temperature, cells cultured onpNIPAM spontaneously detach as a confluent sheet. In comparison, cells grown on TCPS remain attachedindefinitely after the temperature drop, requiring enzymatic or mechanical removal. In this work, wepresent an examination of the response of bovine aortic endothelial cells (BAECs) and extracellular matrix(ECM) proteins to plasma polymerized NIPAM (ppNIPAM) surfaces using X-ray photoelectron spectroscopy(XPS), time-of-flight secondary ion mass spectrometry (ToF-SIMS), and immunostaining. Immunoassayresults reveal that, although fibronectin, laminin, and collagen closely associate with the cell sheet, somecollagen may be associated with the surface, as well. Our XPS results indicate that ppNIPAM surfacesafter cell liftoff differ from their blank counterparts, the primary distinction being the presence of amideand alcohol species on ppNIPAM surfaces used for cell culture, possibly owing to the presence of aproteinaceous film. Finally, a comparison between ppNIPAM-treated surfaces used for cell culture versuscontrol surfaces by principal component analysis of the ToF-SIMS data confirms that the surfaces differ;the presence of molecular ion fragments from amino acids (e.g., alanine, glycine, and proline) is the chiefreason for this difference. Therefore, from our surface characterization of ppNIPAM-coated TCPS aftercell liftoff, we conclude that although low-temperature liftoff of the BAEC monolayer is accompanied bythe majority of the components of the ECM, some of the ECM proteins still remain at the surface.
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