Electrochemical surface plasmon resonance biosensor for study of DNA desorption and hybridization

We report a system, which combines electrochemical and surface plasmon resonance (SPR) techniques on the same sensing chip. Each channel of a four-channel laboratory SPR sensor is supplemented with two planar gold electrodes (the reference and the counter electrodes), whereas the gold layer of SPR chip is used as the working electrode. A custom electronics enables to set an arbitrary potential between the reference and working electrodes and to measure the current flow between the counter and the working electrodes. Information from standard electrochemical techniques, i.e. cyclovoltammetry and chronoamperometry can be acquired with the system while simultaneously monitoring the shift in the surface plasmon resonance. The electrochemical SPR biosensor was used to study desorption of thiolated DNA probes with a negative potential. By comparing the acquired electrochemical and SPR signals, we show that DNA probes as well as a monolayer of alkanethiols can be desorbed by applying negative potentials to the SPR chip surface. Moreover, it is shown that the DNA probes can be reabsorbed on the SPR sensor surface and the complementary DNA can be detected without loss in detection sensitivity.