Monocyte activation on titanium-sputtered polystyrene surfaces in vitro: The effect of culture conditions on interleukin-1 release

The release of interleukin-1 alpha (IL-1 alpha) by human peripheral blood monocytes cultured for 24 and 48 h on polystyrene (PS) and titanium-sputtered polystyrene (Ti) was evaluated. Magnetron sputtering of the PS surfaces resulted in a formation of a 50-nm-thick coat, consisting of an outer layer of TiO2. Monocytes released IL-1 alpha without the addition of exogenous stimuli. A doubling of the culture time from 24 to 48 h did not have a major effect on the amount of IL-1 alpha released. The IL-1 alpha levels were increased by addition of lipopolysaccharide (LPS). High concentrations of PS particles (1 and 3 mu m diameter) were equally effective stimuli for IL-1 alpha release as LPS. Preadsorption of fibronectin to culture plates augmented LPS-stimulated IL-1 alpha secretion, whereas preadsorbed fibrinogen had an inhibitory effect. Our observations indicate a direct activation of monocytes by PS and Ti, resulting in IL-1 alpha secretion, which is modified by protein adsorption and exogenous stimuli.