A nanostructured microfluidic device for plasmon-assisted electrochemical detection of hydrogen peroxide released...

Non-invasive liquid biopsies offer hope for a rapid, risk-free, real-time glimpse into cancer diagnostics. Recently, hydrogen peroxide (H₂O₂) was identified as a cancer biomarker due to its continued release from cancer cells compared to normal cells. The precise monitoring and quantification of H₂O₂ are hindered by its low concentration and the limit of detection (LOD) in traditional sensing methods. Plasmon-assisted electrochemical sensors with their high sensitivity and low LOD make a suitable candidate for effective detection of H₂O₂, yet their electrical properties need to be improved. Here, we propose a new nanostructured microfluidic device for ultrasensitive, quantitative detection of H₂O₂ released from cancer cells in a portable fashion. The fluidic device features a series of self-organized gold nanocavities, enhanced with graphene nanosheets having optoelectrical properties, which facilitate the plasmon-assisted electrochemical detection of H₂O₂ released from human cells. Remarkably, the device can successfully measure the released H₂O₂ from breast cancer (MCF-7) and prostate cancer (PC3) cells in human plasma. Briefly, direct amperometric detection of H₂O₂ under simulated visible light illumination showed a superb LOD of 1 pM in a linear range of 1 pM-10 μM. We thoroughly studied the formation of self-organized plasmonic nanocavities on gold electrodes via surface and photo-electrochemical characterization techniques. In addition, the finite-difference time domain (FDTD) simulation of the electric field demonstrates the intensity of charge distribution at the nanocavity structure edges under visible light illumination. The superb LOD of the proposed electrode combining gold plasmonic nanocavities and graphene sheets paves the way for the development of non-invasive plasmon-assisted electrochemical sensors that can effectively detect low concentrations of H₂O₂ released from cancer cells.