Electrochemistry-Assisted Surface Plasmon Resonance Biosensor for Detection of CA 15-3

In this work, we describe an innovative methodology based on combined surface plasmon resonance (SPR) and electrochemical responses (eSPR) in the same immunoassay for screening CA 153 cancer biomarker with high sensitivity (and selectivity), in a very simple, label-free, accurate, and fully automated manner. Detection was achieved by performing two simple steps. In the first step, direct SPR was used to monitor CA 153 interaction with surface immobilized antibody. Two linear response ranges were obtained and the detection limit achieved is poor (LOD of 21 U mL1). However, in the second detection step, electrochemical measurements at the SPR gold surface were performed to measure the decrease of redox probe peak current upon antigenantibody interaction, providing a suitable amplification strategy to lower detection levels of CA 153 (LOD of 0.0998 U mL1), without the need of additional complex and/or expensive amplification steps to enhance the sensitivity. Moreover, selectivity studies were performed against other common cancer biomarkers and the results showed that the eSPR immunosensor is selective for the CA 153 protein. Finally, the clinical applicability of the developed eSPR biosensing methodology was successfully applied to detect CA 153 in human serum samples at clinically relevant levels due to the high sensitivity of electrochemical readout. The same concept may be further extended to other proteins of interest.
This research had the financial support of FCT (Fundaca̧õ para a Ciencia e Tecnologia) and co ̂ financed by the European Union (FEDER funds) under the Partnership Agreement PT2020, Research Grants Pest-C/QUI/UIDB/00081/2020 (CIQUP) and NORTE-01-0247-FEDER-017834 (project RamSERS). J.A.R. (ref SFRH/BPD/105395/2014) and C.M.P. (ref SFRH/BSAB/150320/2019) acknowledge FCT under the QREN − POPH − Advanced Training, subsidized by European Union and national MEC funds. We thank BioMark/ISEP researchers Felismina Moreira and Joana Guerreiro for all the support to perform the ellipsometry measurements
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