The effect of protein adsorption on substratum surface free energy, infrared absorption and cell spreading

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Abstract
In this study we determined the influence of protein adsorption on substratum surface free energy, infrared absorption and cell spreading. We adsorbed bovine serum albumin, bovine fibronectin and foetal bovine serum during two hours onto three substrata: fluoroethylenepropylene copolymer, a low surface free energy material, polyvinylfluoride, a medium surface free energy material, and tissue culture polystyrene, a high surface free energy material. We determined the influence of protein adsorption by means of Fourier Transformed Infrared Spectroscopy (ATR‐mode), by measuring the changes in substratum surface free energy and by deterniining the equilibrium spreading of fibroblasts (approximately 2 h) from RPMI 1640 medium. Infrared spectra showed Amide I and Amide II bands, indicative for protein adsorption, located at different wavenumbers for different substrata. After protein adsorption, substratum surface free energies converged slowly, but a distinct influence of the bare substratum surface free energy remained. Ceil spreading slightly increased on protein‐coated substrata, but remained according to the pattern expected on basis of the surface free energy of the uncoated substrata, i.e. low on low‐energy substrata and high on high‐energy substrata. Only fibronectin caused a significant increase in cell spreading, possibly due to the specific interaction of adsorbed fibronectin with specific cellular receptors.