Biotinylated polypyrrole modified quartz crystal microbalance for the fastand reagentless determination of avidin concentration

A quartz crystal microbalance (QCM) bioaffinity sensor for avidin, based on electropolymerized biotinylated polypyrrole film, was developed. The funct ionalization of one of the Au quartz electrode has been achieved by control led potential oxidation of a biotinyl pyrrole monomer in CH3CN. The modifie d quartz resonator was placed in a QCM flow cell. In the presence of avidin solutions, gravimetric measurements indicated the reproducible formation o f a compact avidin layer via the specific avidin-polymerized biotin interac tion. The polymerized biotin retained identical bioaffinity properties for avidin over a period of one month. The initial slope of the frequency chang e as a function of time was recorded and related to avidin concentrations. Avidin concentration in the range 1.5 x 10(-9)-3.7 x 10(-5) M can be measur ed by this method.