Adhesion of L1210 cells to sulfonated styrene copolymer surfaces in the absence of serum

Abstract

The initial adhesive interaction of living L1210 cells with sulfonated surfaces of (styrene/methyl methacrylate) copolymers (S/MMA), in the absence of serum in the medium, was examined. The surfaces of S/MMA copolymers were modified by sulfonation with sulfur trioxide at the gas/copolymer interface. The variation in styrene content in the copolymer (from 5 to 50 mol% of styrene) causes a change of the content of sulfonic groups bonded to the aromatic rings of styrene at the copolymer surface. It was shown by means of X-ray photoelectron spectroscopy that the sulfur atomic concentration S increases linearly with the styrene mer content in the copolymer. It was also shown that the contact angle θ of water on the surfaces is a decreasing linear function of S. Cells were allowed to interact with the surfaces, under stationary conditions for time t int up to the moment at which the shearing force F, caused by the medium flow, was started. The early adhesion of cells to the surfaces was examined ( t int was within the range of seconds), and the results were expressed by means of a quantity A as a function of one variable, for various empirical variables. The quantity A is defined as a ratio of the number of cells adhering to the surface during t int and remaining adherent despite the application of F, to the number of sedimented cells. The following results were obtained. (1) The function A( t int) increases and reaches a plateau at 100% adhesion. For the surfaces of wettability characterized by θ = 58°, 52° and 12°, the times t int of reaching the plateau are in the ratio of 12:9:1, respectively. (2) The function A( F) decreases for the surfaces of low wettability. (3) The function A( S) linearly increases and the function A( θ) linearly decreases, owing to the increase in the SO 3H group content at the surfaces. Results (1) and (3) are obtained at F = 3.9 × 10 −9 N, and results (2) and (3) at t int = 10 s. The Brownian motion of cells was examined. For its duration d, from the moment of cell sedimentation onto the surface to the moment of the absence of determinable cell oscillations, it was shown that the function d( S) linearly increases while the function d( θ) linearly decreases. It was shown that the initial contact of living L1210 cells with the substratum, in the absence of serum proteins, is affected by sulfonic groups. The number of cells strongly adhering, within a few seconds, to the S/MMA copolymer surfaces increases linearly with the content of the sulfonic groups at these surfaces.