SPR could be used in association with electrochemistry (EC-SPR) where the thin metal film on the
substrate is used not only to excite surface plasmons, but also acts as a working electrode for
electrochemical detection or control [109,110]. With the EC-SPR configuration is possible to
simultaneously obtain information about the electrochemical and optical properties of films with
thicknesses in the nanometer range (Figure 2D). Georgiadis et al. and Heaton et al. monitored the in
situ hybridization of DNA in the presence of different electrochemical fields [109,110].
The mass of the absorbed molecules is the measured parameter also in the piezoelectric sensors.
The method used is based on the change in oscillating frequency resulting from the increase in mass on
the crystal surface, which accompanies the hybridization. A quartz crystal microbalance affinity
biosensor was used by Mannelli and collaborators to detect genetically modified organisms [105] and
recently chemically modified piezoelectrodes were utilized to develop a biosensor for the
determination of genetically modified soybean [106]. This approach is used for the identification of
genetically modified organisms (GMOs) because the production of GM crops is increasing and there is
a growing requirement for methodologies that allow the accurate and easy determination of the content
of GMOs [111].