ABSTRACT
AIM: von Willebrand factor (VWF) plays an important role in the regulation of hemostasis and thrombosis formation, particularly under a high shear rate. However, the adhesive force due to the molecular interaction between VWF and glycoprotein Ibα (GPIbα) has not been fully explored. Thus, we employed atomic force microscopy to directly measure the adhesive force between VWF and GPIbα. METHODS: We measured the adhesive force between VWF and GPIbα at the molecular level using an atomic force microscope (AFM). An AFM cantilever was coated with recombinant N-terminus VWF binding site of GPIbα, whereas a cover glass was coated with native VWF. RESULTS: The adhesive force at the molecular level was measured using an AFM. In the presence of 1 µg/mL VWF, the adhesion force was nearly 200 pN. As per the Gaussian fit analysis, the adhesive force of a single bond could have been 54 or 107 pN. CONCLUSION: Our consideration with the Gaussian fit analysis proposed that the adhesive force of a single bond could be 54 pN, which is very close to that obtained by optical tweezers (50 pN).
Subject(s)
Blood Platelets/metabolism , Hemostasis/physiology , Microscopy, Atomic Force/methods , Platelet Glycoprotein GPIb-IX Complex/chemistry , Thrombosis/blood , von Willebrand Factor/chemistry , Blood Platelets/ultrastructure , Humans , Molecular Structure , Platelet Glycoprotein GPIb-IX Complex/ultrastructure , Thrombosis/diagnosis , von Willebrand Factor/ultrastructureABSTRACT
The performance of hepatitis B surface antigen (HBsAg) screening assays is continuously improved to reduce the risk of transfusion-associated hepatitis B. In this study, a semiautomated immune complex transfer chemiluminescence enzyme immunoassay (ICT-CLEIA) for the detection of HBsAg, which is as sensitive as hepatitis B virus (HBV) DNA PCR, was developed; the ICT-CLEIA assay performance was compared with the performance of the Architect HBsAg QT assay and HBV DNA PCR. The specificities in the initial assay and after retesting were 99.50% (1,988/1,998 samples) and 99.95% (1,997/1,998 samples), respectively. The analytical detection limit was determined to be 0.2 mIU/ml using the 2nd International WHO HBsAg standard, and the cutoff value (0.5 mIU/ml) of the ICT-CLEIA assay was 8.0 standard deviations (SD) above the mean of the HBsAg-negative specimens. The ICT-CLEIA assay could detect HBsAg even in the presence of anti-HBs antibodies and demonstrated a 23.6-day-shorter window period using commercially available HBsAg seroconversion panels than the Architect HBsAg QT assay. Furthermore, the monitoring of the viral kinetics by the ICT-CLEIA assay and the HBV DNA PCR produced very similarly shaped curves during both the HBsAg seroconversion and reverse seroconversion periods. Therefore, the ICT-CLEIA assay may be useful not only for an earlier detection of HBV reactivation but also for the monitoring of hepatitis B patients.
