Kinetics Of Adsorption Of Proteins From Human Plasma Onto Foreign Surfaces

It is believed that adsorption of proteins is the first occurrence after blood/foreign surface contact. The composition of the protein layer, how it depends on surface properties, and how it changes with time are essentially unknown. The objective of this work was to develop data relevant to these questions. To this end, the quantities of �albumin, fibrinogen and IgG adsorbed on seven surfaces from human plasma as a function of time were measured. Human plasma (ACD anticoagulant) was diluted 1:4 with tris buffer. Purified proteins were labelled with iodine isotopes using the IC1 method and added to the plasma as tracers. Materials studied include several segmented polyether-urethanes, both hydrophilic and hydrophobic, glass, siliconized glass (SG), polystyrene (PS) and polyethylene (PE). The results may be summarized as follows: Fibrinogen: Within the 2 min to 3 h range of contact times, fibrinogen was not detected on any of the hydrophilic surfaces. On PE and SG the quantity adsorbed passed through a maximum between zero time and 2 min, then declined to near zero. Only on PS was adsorption substantial (0.4 μg cm-2) and constant with time, similar to that from a solution of fibrinogen. Albumin: Albumin was also not detected on the hydrophilic materials. In general its surface concentration when it was adsorbed (hydrophobic surfaces) was similar to that observed for solutions of albumin. IgG: IgG was detected on all surfaces. The surface concentrations were low (about 0.1 μg cm-2) compared to solution values but were generally constant with time. The following conclusions are drawn: (1) The plasma itself modifies adsorption. Therefore solution adsorption data cannot be used to predict plasma adsorption. (2) Contrary to popular belief, fibrinogen is absent or transient on most surfaces. (3) IgG appears to be ubiquitous as a component of protein layers adsorbed from Plasma.