Electrochemical enhanced plasmonic optical fiber grating sensor for cancer biomarker detection

Plasmonic optical fiber Bragg gratings offer a large range of opportunities in many biosensing applications by providing well-suited solutions for continuous and accurate monitoring. One of the most preferred configurations relies on surface plasmon resonance (SPR) implemented on tilted fiber Bragg grating (TFBG) by covering it with a very thin metal sheath (mostly gold), responsible for a drastic sensitivity improvement. When bioreceptors are immobilized onto the sensitive area, a plasmonic TFBG-based sensor leads to a highly sensitive and specific biosensor. Nevertheless, all possibilities using such a versatile platform were not totally investigated yet. Indeed, in addition to generate a plasmonic effect, the gold layer can also serve as a working electrode in an electrochemical set-up. By applying an electric field, it is possible to attract and detect molecules in solution. In this work, we developed the technique in the frame of the detection of the HER2 (Human Epidermal Growth Factor Receptor-2) protein, a relevant biomarker in breast cancer diagnosis. For that purpose, we biofunctionalized the probe using anti-HER2 aptamers with a high affinity to HER2 before performing a specific electrophoresis on gold-coated gratings. Results show a significant improvement in the sensitivity in comparison with the common non-electrochemical approach. The strength of this new sensing method is based on the ability to tweeze and detect targeted biomarkers with the same sensor. This method opens the way to more robust and reliable biosensing measurements with enhanced sensitivity.