THE EFFECT OF PROTEIN ADSORPTION ON APO-B REMOVAL AND SELECTIVITY IN PLASMA FRACTIONATION BY MEMBRANE

This paper investigates the contribution of adsorption of lipoproteins and albumin to the selectivity and removal efficiency of cellulose diacetate plasma fractionation membranes. These membranes are used in the second stage of cascade filtration for selective plasma treatment. Human plasma from donors was used with waste retentate from hypercholesterolemic patients to increase ApoB concentration, and was circulated in vitro through the test filter while recycling both permeate and retentate. The amount of adsorbed protein was calculated from the protein loss in the tank, taking into account the mass extracted in the collected samples. The loss of ApoB was high and reached 40% of the initial mass of ApoB after the processing of one tank volume of plasma (defined to have a volume to surface ratio of 3 l/m2), and the losses of ApoA1 and albumin were respectively 15% and 6%. For ApoB the time rate of adsorption reached a maximum after 20 min of filtration, and adsorption was complete after 1 h. When the same experiments were run in cross-flow mode, with the retentate discarded, it was found that adsorption accounted for almost 50% of total removal of ApoB and ApoA1. In cross-flow filtration, the selectivity of fractionation between ApoB and ApoA1 was higher (42%) than when the retentate was recycled. A model for predicting protein loss in the reservoir was set up, and yielded a good agreement with data for cross-flow filtration but underestimated adsorption when retentate was recycled.