Quantification of plasma-derived blood coagulation factor VIII by real-time biosensor measurements

Plasma-derived blood coagulation factor VIII was analyzed in real time usin g biosensor technology. Monoclonal antibodies directed against the heavy an d against the light chain of factor VIII were immobilized on different carb oxymethyl dextran surfaces. Different factor VIII concentrations were injec ted over the antibody surfaces in parallel acid response levels were determ ined from the dissociation phase at a fixed time after sample injection. Se rial dilutions of plasma-derived factor VIII with known concentrations dete rmined by a commercial FVIIIC:Ag ELISA were used as standards. A quantifica tion limit of 0.9 I.U./ml with antibody 530p and 1.5 I.U./ml with antibody 531p was calculated. Intra-assay precision expressed as percent coefficient of variation was below 10% for concentrations above 0.6 I.U./ml. Inter-ass ay precision for antibody 530p was below 20% for concentrations higher than 0.6 I.U./ml. For 531p, inter-assay precision was below 10% for concentrati ons higher than 2 I.U./ml. A sensor chip lifetime in respect to regeneratio n of at least 100 cycles for both antibodies was found. The small sample re quirement of 35 mul allows fast analysis of different FVIII products and th e use of two monoclonal antibodies directed against two different FVIII dom ains provides additional information about the integrity of the FVIII molec ule. (C) 2001 Elsevier Science B.V. All rights reserved.