Isolation and some of the physicochemical and immunologic properties of a platelet adhesion inhibitor from human serum

Passivating protein coatings for implantable glucose sensors: Evaluation of protein retention

The long-term function of implantable biosensors is limited by the foreign-body reaction (FBR). Since the acute phase of the FBR involves macrophage attachment mediated by adsorbed fibrinogen, preadsorption, and retention of other proteins might reduce the FBR. The retention of preadsorbed albumin, hemoglobin, von Willebrand's factor, and high-molecular-weight kininogen was therefore measured after exposure to plasma. The retention of preadsorbed proteins after incubation with monocyte cultures and implantation in rats was also measured. Fibrinogen adsorption from plasma to the preadsorbed surfaces was also measured. Hemoglobin adsorption was higher than that for other proteins, and it also had the greatest retention after exposure to blood plasma. When surfaces preadsorbed with hemoglobin were incubated with monocytes, more of the hemoglobin was displaced than that after incubation in plasma, while still more hemoglobin was displaced when the surfaces were implanted in vivo. Protein preadsorption on polystyrene greatly reduced fibrinogen adsorption. However, polyurethane surfaces used for glucose sensors had low fibrinogen adsorption compared with polystyrene, and this low level was not further reduced by preadsorption with other proteins. Preadsorbed proteins on polymers appear to be removed by passive exchange and/or displacement by plasma proteins and by proteases released by monocytes.

Disulfide linking of albumin to the hinge region of immunoglobulin G in normal human serum

A protein-protein complex from human serum was isolated and characterized as a two-component system, containing albumin and IgG in a 1:1 mole ratio. The observations reported here suggest that the albumin-IgG complex may have formed through intermolecular disulfide bonds between albumin and IgG. Immunoelectrophoretic analysis of papain-digested fragments of albumin-IgG complex revealed that the combining sites for albumin may be located in the hinge region between the Fab and the Fc fragments of IgG.