Determination of fibrinogen content in cryoprecipitated antihemophilic factor by fluorescence quenching method

Objective To establish a new method for the determination of fibrinogen content in cryoprecipitated antihemophilic factor. Methods Fibrinogen (Fib) could bind with sheep anti-human fibrinogen (anti-Fib) specifically and further form antigen-antibody complex. When the Fib was present in the solution, the fluorescence of fluorescein isothiocyanate (FITC) labeled on the anti-Fib (FITC-anti-Fib) was quenched due to the formation of immune complex. The fluorescence quenching degree of FITC-anti-Fib was positively correlated with Fib concentration (cFib) in a certain concentration range. Results The linear relationship between fluorescence quenching degree [(I0-I)/I0] of FITC-anti-Fib and ln(cFib) was (I0-I)/I0=15.53ln(cFib)+ 80.79 (R2=0.99) when the cFib was in the range of (0.007 8-0.560 0) g/L. The recovery of Fib was (96.77-102.43) %. When the method was applied to determine Fib at high, medium, and low concentrations, the obtained intra-day variation coefficients were 0.31%, 0.56%, and 0.49%, respectively, and the inter-day variation coefficients were 3.81%, 3.06%, and 4.13%, respectively. There was no significant difference between the results measured by fluorescence quenching method and coagulation method (t=-0.075, P>0.05). Conclusion In this work, a new fluorescence method for the determination of Fib in cryoprecipitated antihemophilic factor was successfully established based on the specific combination of fib and FITC-anti-Fib. The method is simple and rapid. The obtained results were accurate and reliable by using this method to determine Fib.