PROTEIN ADSORPTION AND MACROPHAGE ACTIVATION ON POLYDIMETHYLSILOXANE AND SILICONE-RUBBER

Static and dynamic human blood adsorption studies on polydimethylsilox ane, PDMS, and silicone rubber show that these materials are similar, but not identical, in their protein adsorption behavior. Fibrinogen, i mmunoglobulin 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 prot ein adsorption characteristics for the two materials were similar, hig her levels of the respective proteins were identified on silicone rubb er compared to PDMS. Monocytes/macrophages incubated on PDMS, silicone rubber and low density polyethylene, LDPE, with or without protein ad sorption produced variable levels of IL-I beta, IL-6 and TNF-alpha dep endent on the polymer and adsorbed protein. PDMS showed lower levels o f the cytokines when compared to the polystyrene control and polyethyl ene. Protein preadsorption on the PDMS, polystyrene, and LDPE surfaces showed lower levels of cytokines when compared to the respective quan tities produced with no protein adsorption suggesting a passivating ef fect by the protein adsorption phenomenon on monocyte/macrophage activ ation. Preadsorption of IgG, fibrinogen or fibronectin decreased the q uantitative expression of IL-1 beta but increased the functional activ ity in the thymocyte proliferation assay indicating the presence of mo nocyte/macrophage activation products which either downregulated the a ctivity of IL-1 beta or upregulated thymocyte proliferation in an inde pendent fashion.