Electrochemical surface plasmon resonance sensing with absorptive redox mediator film

Surface plasmon resonance (SPR) spectroscopy has been used for the detection of reversible refractive index changes that occur in a redox mediator film during potentiostatic oxydoreduction. We investigated the theoretical and experimental parameters of electrochemical SPR (eSPR) sensing using as an example of the electroactive labels the Methylene Blue (MB) organic dye. The optimal eSPR interrogation method for MB sensing in a solution and in a uniform interfacial thin film formed by stem-loop oligonucleotides tagged with MB are evaluated. Electrochemical activation of the optical SPR response depends on the local MB concentration and can be used to design sensitive and highly selective biosensing approaches.