Albumin polymers, having an average diameter of 1020 +/- 250 nm, were prepared by the disulfide polymerization of recombinant human serum albumin (rHSA) by controlling of the pH and temperature. Fibrinogen could be conjugated on the surface of an albumin polymer using N-succinimidyl 3-(2-pyridyldithio)propionate (SPDP). Under flow conditions, the fibrinogen-conjugated albumin polymers (fibrinogen-albumin polymers) were irreversibly attached to the platelet-immobilized surface in the reconstituted blood at a low platelet concentration ([platelet] = 5.0 x 10(4)/microL, a 5-fold diluted platelet concentration), and the attachment was suppressed by the addition of anti-GPIIb/IIIa monoclonal antibodies. It was confirmed that fibrinogen-albumin polymers specifically interacted with GPIIb/IIIa expressed on the surface of the activated platelets. Although platelets with a low platelet concentration were hardly attached to the platelet-immobilized surface under the flow conditions, the addition of fibrinogen-albumin polymers enhanced the attachment of the remaining platelets to the surface, indicating that the fibrinogen-albumin polymers would help the hemostatic ability of platelets at the site of vascular injury of patients in thrombocytopenia.