COATING OF HUMAN DECAY-ACCELERATING FACTOR (HDAF) ONTO MEDICAL DEVICES TO IMPROVE BIOCOMPATIBILITY

In passing blood through an artificial circulatory system, the blood i s exposed to surfaces that result in activation of the complement syst em. The consequences of the activation of complement can be extremely serious for the patient ranging from mild discomfort to respiratory di stress and even anaphylaxis. An entirely novel approach was to express recombinant GPI anchored human decay accelerating factor (hDAF) using the baculovirus system and then coat the recombinant protein onto the surfaces of these materials to reduce complement activation. Expressi on of hDAF in Sf9 cells was shown by ELISA, FAGS analysis, and Western blot. Functional activity was tested by CH50 assay. For the coating e xperiments a small scale model of a cardiovascular bypass circuit cons tructed from COBE(TM) tubing was used. hDAF was either coated onto the circuit using adsorption or covalently linked via the photoreactive c rosslinker, p-azidobenzoyl hydrazide. After coating, heparinised human blood was pumped around the circuit and samples were collected into E DTA collection tubes at different time points. Complement activation w as measured using a Quidel(TM) C3a-des-arg EIA. The photolinked circui ts gave a reduction in C3a production of 20-50%, compared to 10-20% se en with an absorbed hDAF circuit. Furthermore, the inhibition of compl ement was seen over the whole time scale of the photolinked circuit, 6 0-90 min, whilst in the adsorbed circuit inhibition was not seen to a significant degree after 60 min. The time scale of a standard cardiac bypass is 45-90 min, therefore, the photolinked circuit results are en couraging, as significant inhibition of complement activation is seen within this time frame. (C) 1997 Elsevier Science B.V.