Study On QCM Immunosensor For The Detection Of Estradiol

In this paper, a piezoelectric immunosensor was developed for detection of estradiol(E2). The QCM-chip was self-assembly modified with mercaptopropionic acid(MPA) followed by the activation with carbodiimide(EDC) / n-hydroxylsuccin- imide(NHS) to immobilize the E2-antibody. The resonant frequency shift resulted from the binding of E2 with the immobilized antibodies was correlated to the antigen concentration. The building up of the sensing matrix was confirmed by the electrochemical impedance spectroscopy(EIS). Two analytical modes, equilibrious or dynamic mode, were explored. The output Δf responds to the concentration of E2 with a detection limit of 0.04 μg/mL and a linear range of 0.1 to 10 μg/mL with the equilibrious mode. Besides, under the manner of immersion dynamic analysis, the presence of E2 induced in a synchronous sensing output along with the incubation of Ag-Ab affinity reactions. During the first dozens of seconds, there is a linearly increased output on sensing-chip depended on the time, and the slope of this output is in linear relation with the concentration of E2 with a detection limit of 0.06 μg/mL. Thus, a faster sensing technique is established for rapid analysis required only several seconds other than the dip-and-dry mode which needs a complete incubation period for at least 60 minutes. This finding greatly promoted the applicability of immunosensor for rapid, real-time or in-site analysis.