Correlation of the Adhesive Properties of Cells to N-Isopropylacrylamide/N-tert-Butylacrylamide Copolymer Surfaces with Changes in Surface Structure Using Contact Angle Measurements, Molecular Simulations, and Raman Spectroscopy

• Published in: Chemistry of materials Vol. 17; no. 15; pp. 3889 - 3898
• Main Authors: Lynch, Iseult, Blute, Irena A, Zhmud, Boris, MacArtain, Paul, Tosetto, Miriam, Allen, Lorcan T, Byrne, Hugh J, Farrell, Garrett F, Keenan, Alan K, Gallagher, William M, Dawson, Kenneth A
• Format: Journal Article
• Language: English
• Published: American Chemical Society 26.07.2005
• Subjects: Chemical Sciences; Kemi; Materialkemi; Materials Chemistry; Natural Sciences; Naturvetenskap
• ISSN: 0897-4756; 1520-5002
• DOI: 10.1021/cm0506959

A series of copolymers of N-isopropylacrylamide (NIPAM) and the more hydrophobic comonomer N-tert-butylacrylamide (NTBAM), with increasing NTBAM content (i.e., increasing hydrophobicity) were prepared. The adhesion of human epithelial cells on polymer films prepared from copolymers of NIPAM:NTBAM was observed to increase with increasing polymer hydrophobicity. However, in the absence of serum, cell adhesion to the different surfaces was statistically indistinguishable. Thus, it appears that the copolymer films differentially support cell adhesion due to selective adsorption of proteins from the physiological environment (the serum). Using contact angle measurements, molecular simulations, and Raman spectroscopy to characterize the different surfaces, we show evidence that the different behavior of cells on the films of increasing hydrophobicity is actually due to the different chemical properties of the surfaces with increasing content of NTBAM in the copolymers. As the NTBAM content is increased, the number of NH residues at the surface decreases, due to the additional steric hindrance of the bulkier NTBAM group, which results in decreased hydrogen bonding and thus decreased adsorption of proteins such as albumin. However, in some cases, the adsorption is driven by hydrophobic interactions, and proteins such as fibronectin were found to adsorb more to the films with a higher content of NTBAM. There appears, thus, to be a direct correlation between surface composition, i.e., the functional groups exposed at the surface, and protein binding and subsequent cell adhesion.