The dual-modes of QCM immunosensing for estradiol analysis via dynamic or round-off calibration

Abstract

ABSTRACTIn this work, a piezoelectric immunosensor is developed for the detection of estradiol (E2). The gold-coated chip of quartz crystal microbalance was modified by a 3-mercaptopropionic acid self-assembly monolayer, activated by carbodiimide/n-hydroxylsuccinimide, and then to immobilise the E2 antibody via the interaction with their amine groups. The resonance frequency change resulted by the binding of E2 on immobilised antibody differs from that of a blank (ΔF), was correlated to the antigen concentration. The construction of the sensing interface was confirmed by electrochemical impedance spectroscopy. Both round-off or dynamic modes were explored as analytical detection strategy in this work. Using round-off mode, the output ΔF responds to the concentration of E2 with a detection limit of 0.04 μg mL−1 and a linear range from 0.1 to 10 μg mL−1. Meanwhile, using a dynamic mode, the presence of E2 induced in a real-time sensing output along with the incubation of antigen. The slope of sensing output is in linear relation with the concentration of E2 with a detection limit of 0.06 μg mL−1. Thus, a faster immunesensing technique is established for rapid analysis requiring only several seconds other than the round-off mode which needs a complete incubation period for at least 60 min. This finding will greatly promote the applicability of immunosensor for rapid, real-time or in-site assays.