(193h) Electrochemical Piezoelectric Cantilever Sensors: Vibration-Induced Release from Biosensor Surface

Objectives.  The
objective of this study is to develop a sensor that uses the principles of
cantilever mechanics and electrochemical impedance spectroscopy (EIS) for detecting
a biological analyte, and to subsequently release it through cantilever
resonance vibration. The ?de-binding' technique can be used as a confirmation
step, or to regenerate the sensing surface. The model analytes used in this
study to demonstrate the principles are:  Protein G and E. coli O157:H7.

Methods. Piezoelectrically-excited
cantilevers were designed with a sputtered gold electrode to facilitate
impedance spectroscopy measurements at the cantilever surface. Impedance
spectroscopy was used in tandem with classic dynamic cantilever resonance for
detecting target analyte; the measured resistance to charge transfer from the
electrode to ferricyanide in solution, and cantilever
resonant frequency served as the measured signals of the two techniques,
respectively. All resonant frequency and EIS measurements were conducted within
a specially-designed flow cell, which incorporated a reference electrode,
platinum counter electrode, and the sensor gold surface as a working electrode.
After Protein G or E. coli O157:H7
were attached to the sensor surface, the applied excitation potential which
induces vibration due to the bonded piezoelectric material to the glass
cantilever, was increased until the surface acceleration was sufficient to release
the target analytes. Finite element modeling was employed to evaluate the
relative surface accelerations for various dynamic modes present in liquid.

Results. The immobilized Protein G or E. coli cells were removed from the
sensor electrode when the excitation potential was increased from 100 mV to 10
V, with the assistance of a negative DC potential applied to the electrode. The
resistance to charge transfer decreased by ~ 40% when the 10V excitation
potential was applied to a sensor saturated with Protein G with the assistance of
a  -700 mV DC potential applied to the
electrode. Little to no removal of analyte was observed with the DC potential
alone. The signal returned to its original value when the surface was exposed
to fresh Protein G, indicating regeneration of the sensing surface.

 Conclusion. . The vibration of the
piezoelectric sensor triggered release of the physisorbed Protein G and
antibody-bound E. coli with the
assistance of electrostatic repulsion. The vibration-induced release approach
is useful for repeated sensing requirement applications, and can be used to
separate dilute analytes from complex matrix. 
We show in this study that sensor surface can be regenerated.