Protein adsorption and macrophage activation on polydimethylsiloxane and silicone rubber

Static and dynamic human blood adsorption studies on polydimethylsiloxane, PDMS, and silicone rubber show that these materials are similar, but not identical, in their protein adsorption behavior. Fibrinogen, immunoglobulin G, and albumin were the predominant proteins identified on the material surfaces with fibronectin, Hageman factor (factor XII), and factor VIII/vWF adsorbing at intermediate levels. While the protein adsorption characteristics for the two materials were similar, higher levels of the respective proteins were identified on silicone rubber compared to PDMS. Monocytes/macrophages incubated on PDMS, silicone rubber and low density polyethylene, LDPE, with or without protein adsorption produced variable levels of IL-1 beta, IL-6 and TNF-alpha dependent on the polymer and adsorbed protein. PDMS showed lower levels of the cytokines when compared to the polystyrene control and polyethylene. Protein preadsorption on the PDMS, polystyrene, and LDPE surfaces showed lower levels of cytokines when compared to the respective quantities produced with no protein adsorption suggesting a passivating effect by the protein adsorption phenomenon on monocyte/macrophage activation. Preadsorption of IgG, fibrinogen or fibronectin decreased the quantitative expression of IL-1 beta but increased the functional activity in the thymocyte proliferation assay indicating the presence of monocyte/macrophage activation products which either downregulated the activity of IL-1 beta or upregulated thymocyte proliferation in an independent fashion.