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The suitability of polymeric biomaterials as surfaces for the attachment and growth of cells has often been investigated in tissue culture. In this study the contribution that adsorption of serum fibronectin (Fn) or vitronectin (Vn) make to the attachment and spreading of fibroblast cells during the first 90 min following seeding was determined for two modified tissue culture polystyrenes, as model biomaterial surfaces. The amount of serum Vn and Fn which adsorbed onto tissue culture grade polystyrene (TCP) from different serum concentrations over the range of 0.1-30% (v/v) were determined and compared to attachment of cells of the BHK-21 and HT1080 fibroblast lines. There was no simple correlation between the amount of Fn or the amount of Vn adsorbed and cell attachment and spreading. The requirement for Fn or Vn for attachment and spreading of BHK-21 or HT1080 cells onto modified polystyrene (either TCP or to Primaria) during the first 90 min of cell culture was directly tested by selective removal of Fn or Vn from the serum prior to addition to the culture medium. Attachment and spreading of BHK-21 or HT1080 cells onto TCP or Primaria surfaces were reduced in a concentration-dependent manner when the cells were seeded in medium containing 2% (v/v) or higher concentrations of Vn-depleted serum. BHK-21 cells or HT1080 cells seeded in medium containing Fn-depleted serum (which contained Vn) attached and spread onto TCP or Primaria. Both BHK-21 cells and HT1080 cells failed to attach to TCP or Primaria when seeded in medium containing serum depleted of both Vn and Fn. The requirement for serum Vn or Fn for fibroblast attachment to TCP was also tested using cells of a human dermal fibroblast strain. The attachment of the dermal fibroblasts to TCP during the first 90 min of culture was not decreased by depletion of Vn from the 15% (v/v) serum, but there was a reduction in the proportion of the attached cells which had spread. Selective depletion of serum Fn did not have any effect on either cell attachment or spreading. Our results show that for fibroblast cells, particularly with cell lines such as BHK-21 or HT1080 but also with cell strains, the first binding of cells onto tissue culture polystyrene when plated in medium containing serum is a result of adsorption onto the surface of serum Vn. The adsorption of serum Vn onto the surface overcomes the effect of serum components which tend to decrease cell attachment.

Tissue culture polystyrene (TCPS) supports good attachment of adherent cells whereas unmodified polystyrene (PS) does not, but the mechanism of this difference is not well characterized. We have compared TCPS and PS for the amounts of vitronectin (Vn) and fibronectin (Fn) which adsorb from the fetal bovine serum (FBS) component of the culture medium. The significance of the amounts of Vn and Fn which adsorbed onto TCPS and PS was determined by reference to the concentration dependence of the cell attachment activity of Vn and Fn when adsorbed onto TCPS and PS, assayed using human vein endothelial cells and BHK-21 fibroblasts. The amount of Vn which adsorbed onto TCPS from medium containing 3-30% (v/v) FBS was supraoptimal for the attachment of endothelial cells and fibroblasts. On PS, the amount of Vn which adsorbed from this medium was less than for TCPS and was suboptimal for cell attachment. Higher levels of Fn adsorbed onto TCPS than to PS, but even the amounts of Fn which adsorbed onto TCPS were suboptimal for cell attachment. We propose that the principal mechanistic difference between TCPS and PS for the initial attachment and spreading of cells is that more Vn adsorbs onto TCPS from the serum component of the culture medium.

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